Subject: 2005 UNITED STATES ANIMAL HEALTH REPORT
Date: October 13, 2006 at 11:25 am PST
2005 UNITED STATES ANIMAL HEALTH REPORT
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BSE Surveillance
Since 1990, the U.S. Department of Agriculture (USDA)
has taken aggressive measures to prevent the introduction
and potential spread of BSE. Following confirmation
of BSE in an imported cow in December 2003, USDA
designed and implemented an Enhanced BSE Surveillance
Program to more accurately determine the level of disease
present in the U.S. cattle population.
The Enhanced BSE Surveillance Program tested as many
cattle as possible in the targeted high-risk population
beginning June 1, 2004. Collection at an enhanced level
has continued beyond 18 months to ameliorate concerns
of trading partners. Experience in the United Kingdom
and Europe has shown that, if present, BSE is most likely
to be detected in adult cattle exhibiting clinical signs
consistent with the disease.
In general, the highest risk categories are adult cattle
showing clinical signs involving the central nervous
system (CNS) and dead and nonambulatory cattle with
clinical signs that could not be adequately evaluated. This
population was estimated to total 445,886 adult cattle per
year in the United States. This number was derived in part
from National Animal Health Monitoring System (NAHMS)
surveys of livestock producers and other estimates.
This estimate includes adult cattle in the following
categories:
Condemned at slaughter for CNS signs;
Moribund, dead, injured, or emaciated (FSIS data
2002);
CNS abnormalities reported for FAD investigations
(APHIS data 2003);
Died onfarm of unknown causes;
Lameness or injury that resulted in euthanasia; and
Cattle that died with signs of incoordination or severe
depression.
The sampling strategy was designed to target animals in
these categories.
Between June 1, 2004, and March 17, 2006, BSE samples
were collected from 5,776 unique locations across the
United States. These locations included slaughter plants,
renderers, farms, public health laboratories, veterinary
diagnostic laboratories, and salvage slaughter (3D–4D)1
plants.
To determine the extent to which the U.S. surveillance is
consistent with OIE guidelines, we have evaluated and
classified surveillance data over the past 7 years according
to OIE standards (table 5).
In May 2005, the OIE general Assembly approved a
new chapter and appendix for BSE surveillance. This
approach assigned point values to each sample, based on
animal age and the subpopulation it was from, and the
likelihood of detecting infected cattle of that age in that
subpopulation. (Prior to May 2005, OIE had recommended
a surveillance level based on the size of the adult cattle
population—for the United States that number was 433
samples with clinical signs consistent with BSE per year.)
Sample values were classified in the OIE system as
belonging to four surveillance strata (streams): clinical
suspect, casualty slaughter, fallen stock, and healthy
slaughter. Samples were also stratified by age.
Cattle were categorized in the clinical suspect stream
if they were submitted under the submission types of
highly suspicious for BSE, rabies suspects, CNS signs,
or antemortem-condemned by FSIS with condemnation
codes for CNS signs or rabies. In addition, many samples
with a clinical history of signs likely to be associated with
BSE were submitted in other categories. Many of these
represented valuable samples, but the OIE definition of
“clinical suspect” did not readily differentiate them from
animals with other clinical signs compatible with BSE.
Some of these cattle were subsequently categorized as
clinical suspects by comparing the likelihood of finding
the signs in histopathologically confirmed cases reported
in the United Kingdom2 with the likelihood of finding
the signs in uninfected animals from the enhancedsurveillance
targeted population. For example, if a sign or
combination of signs were found 30 percent of the time
in BSE cases but only once in every 1,000 uninfected
animals (0.1 percent), then it would be 0.30/0.001 = 300
times more likely to occur in the cases (likelihood ratio =
300 in this case). A likelihood ratio threshold of 807 was
established as a cutoff value for determination of clinical
suspects. This threshold was estimated using input data
from the United Kingdom in the BSurvE3 model, which
provided the average (expected) value for the ratio of
probability of an infected animal showing clinical signs
to an uninfected animal showing clinical signs. Thus, if a
sample was submitted from an animal with combinations
of clinical signs at least 807 times more likely to have
been seen in BSE cases than in the U.S. high-risk
population, it was classified as a clinical suspect.
Cattle with likelihood ratios below the threshold were
allocated into surveillance streams according to the
animal’s submission type as follows:
Submission types of “Nonambulatory” were classified
in the “casualty slaughter” stream;
Submission types of “Other clinical signs that may be
associated with BSE” were classified in the “casualty
slaughter” stream;
Submission types of “FSIS antemortem condemned”
were classified in the “casualty slaughter” stream as
long as the condemnation reason was not “dead”;
Submission types of “FSIS antemortem condemned”
with a condemnation code of “dead” were classified in
the “fallen stock” stream;
Submission types of “dead” were classified in the
“fallen stock” stream;
Submission types of “apparently healthy” were
classified in the “healthy slaughter” stream.
BSE surveillance samples from 1999 through 2003
were collected before the OIE surveillance streams
were established in 2005 and were not submitted with
the same clinical history as that used for the enhanced
surveillance in 2004–05. In order to apply the OIE point
tables, data about these samples were requested from
the National Veterinary Services Laboratories (NVSL) and
were sorted by Centers for Epidemiology and Animal
Health (CEAH) epidemiologists based on the history
included with the sample.
This information is excerpted from the report Summary
of BSE Surveillance in the United States accessed and
available on the Web as of May 2, 2006, at
aphis.usda.gov/newsroom/hot_issues/bse/content/
printable_version/SummaryEnhancedBSE-Surv4-26-
06.pdf>. Details on the Enhanced BSE Surveillance
Program are posted at
issues/bse/BSEOIg.pdf>.
2 Wilesmith, J. W.; Ryan, J. B.; Hueston, W. D. 1992. Bovine spongiform
encephalopathy: case-control studies of calf feeding practices and
meat and bonemeal inclusion in proprietary concentrates. Research in
Veterinary Science 52(3): 325–331.
3 Available, as of April 20, 2006, at . The
BSurvE tool is a Microsoft Excel™ spreadsheet application designed to
estimate BSE prevalence based on targeted sampling strategies.
35 Chapter 2: National Animal Health Surveillance System (NAHSS)
TABLE 5: OIE points from BSE surveillance in the U.S. accumulated for 7 years
Year of testing1
Total
samples2
Clinical
suspects
Fallen
stock
Casualty
slaughter
Healthy
slaughter OIE points3
10/1/05 to 03/17/064 181,564 438 142,337 18,991 19,798 285,491
FY5 2005 413,647 1,527 361,557 50,557 6 899,642
FY 2004 90,085 1,066 62,054 25,096 1,869 592,369
FY 2003 20,778 577 3,106 16,613 482 267,480
FY 2002 20,380 569 2,818 16,045 948 251,740
FY 2001 5,340 665 1 4,515 159 299,177
FY 2000 2,753 664 0 2,064 25 266,891
4/1/99 to 9/30/996 666 265 15 351 35 111,014
Total surveillance
(including enhanced surveillance)
7735,213 5,771 571,888 134,232 23,322 2,973,804
Total for enhanced surveillance only
6/1/04 to 3/17/06
667,767 2,602 559,546 84,534 21,085 1,583,127
1 Testing includes the most recent 7 years of data collected from Apr. 1, 1999, through March 17, 2006.
2 Number of samples and clinical suspects represents animals eligible for surveillance according to the Terrestrial Animal Health Code Article 3.8.4.
3 Note: Animals counted as eligible for OIE points included animals older than 1 year according to the OIE point allocation table. Removal of points from the “juvenile”
category of the OIE points table would decrease the total by 2,843 points. Other documents showing U.S. data may vary due to inclusion or exclusion of young animals.
4 Includes 6 months of fiscal year 2006.
5 The U.S. Government’s fiscal year extends from October 1 through September 30 (e.g., FY 2005 began on 10/1/2004 and ended on 9/30/2005).
6 Includes 6 months of FY 1999.
7 Total includes two positive indigenous animals and one positive animal imported from Canada.
1 3D–4D facilities are slaughter facilities that salvage meat from dead,
dying, disabled, or diseased animals, the meat from which would not
likely pass inspection for human consumption (i.e., edible meat). Much
of this meat goes into either pet food or rendering.
34 2005 United States Animal Health Report
Scrapie Surveillance Evaluation
In general, evaluating a surveillance program entails a
systematic review to assess the degree to which the
program fulfills its stated objectives and meets accepted
surveillance standards. Program strengths and areas for
improvement are identified, and the program’s ability to
adapt to changing situations is evaluated. Evaluating the
surveillance component of one VS program disease was
identified as a key action item in the NAHSS strategic
plan (see
nahss/NAHSS_Strategic_Plan_2005_0216.pdf>).
The surveillance component of the VS scrapie
program was chosen for evaluation. Led by the NSU,
an interdisciplinary working group was developed
consisting of an economist, statistician, several veterinary
epidemiologists, and an industry representative.
The evaluation process focused on four main areas:
surveillance structures (organization and communication),
surveillance processes (data collection, data analysis and
interpretation, and dissemination of results), qualitative
attributes (i.e., simplicity, flexibility, acceptability), and
resource distribution and utilization. Characteristics of the
system were compared with the draft VS Surveillance
Standards, as noted throughout the evaluation.
The evaluation and data gathered focused primarily on the
Regulatory Scrapie Slaughter Surveillance Program testing
and other nonslaughter surveillance testing in sheep
implemented since 2001. Although most of the evaluation
results should be applicable to scrapie surveillance in
goats, this component was not specifically evaluated.
Phone interviews were conducted with State and/or VS
field personnel involved in scrapie surveillance activities
in nine different States representing both APHIS’ Eastern
and Western Regions. Questions addressed the general
objectives, importance, and efficiency of the program; the
communication within the program; and the acceptability,
compliance, and coverage of the program. Personnel
interviewed were assured anonymity.
The evaluation report has been completed and delivered
to VS’ National Center for Animal Health Programs.
snip...
CHAPTER 3
Animal Disease Eradication Programs and Control and Certification Programs
The following Veterinary Services (VS) programs are
designed to eradicate, control, or prevent diseases that
threaten the biological and commercial health of the U.S.
livestock and poultry industries.
Eradication Programs
VS eradication programs include scrapie in sheep and
goats, tuberculosis in cattle and cervids, pseudorabies and
brucellosis in swine, and brucellosis in cattle and bison.
Scrapie in Sheep and Goats
Disease and Program History—Scrapie was first
discovered in the United States in 1947 in a Michigan
flock that, for several years, had imported sheep of
British origin from Canada. Since 1952, VS has worked
to control scrapie in the United States. As a result of
increasing industry and public concern about transmissible
spongiform encephalopathies (TSEs) and the discovery of
new TSE diagnostic and control methods, VS initiated an
accelerated scrapie eradication program in 2000.
Current Program—The primary aspects of the scrapie
eradication program are animal identification, surveillance,
tracing of positive and exposed animals, testing of sheep
and goats in exposed flocks, cleanup of infected flocks,
and certification of flocks.
Animal Identification—Identification of breeding
sheep and culled breeding sheep is mandatory when
ownership changes. The only sheep that do not have to
be identified are those less than 18 months old and, in
the case of ewes, those that also have not lambed or
become pregnant and are in slaughter channels. As of
September 30, 2005, 103,580 premises with sheep and/or
goats were recorded in the scrapie national database. (In
this database, a premises that contains both sheep and
goats might be listed once for each species.) Of these
premises, 73,807 have requested and received official
eartags (tags approved for use by the Animal and Plant
Health Inspection Service [APHIS] in the official scrapie
eradication program).
Regulatory Scrapie Slaughter Surveillance (RSSS)—
The RSSS program, initiated on April 1, 2003, is the
primary surveillance method for scrapie in the United
States. RSSS identifies scrapie-infected flocks through
targeted slaughter surveillance of sheep and goat
populations that have been recognized as having higherthan-
average scrapie prevalence. These are defined as
mature black- or mottle-faced sheep and any mature
sheep or goats showing clinical signs that could be
associated with scrapie, such as poor body condition,
wool loss, or gait abnormalities. Only sheep with some
form of identification (e.g., such as United States
Department of Agriculture [USDA]-approved eartags,
electronic ID, backtags, and tattoos or lot identification)
are sampled. This arrangement allows for tracing positive
animals back to the farm of origin.
During FY 2005, as part of the RSSS program, 30,247
sheep and goat samples, collected from 78 slaughter
plants in 24 States, were tested for scrapie using
immunohistochemistry on brain or lymphoid tissue, or
both. Of the 106 animals diagnosed as positive for scrapie,
93 were black-faced, 11 were mottle-faced, 1 was whitefaced,
and 1 was unknown.
Under the scrapie program, positive test results are traced
back to the animal’s flock of origin, and the flock is placed
under movement restrictions until all high-risk animals
(genetically susceptible females) are removed. High-risk
animals that had been moved from these flocks before
being placed under movement restrictions are traced and
tested.
Testing Summary—In response to epidemiologic
suspicions of disease, field Veterinary Medical Officers
conduct testing to determine if scrapie is present. Such
cases are known as regulatory field cases. In addition to
the 30,247 samples tested under the RSSS program in
2005, about 5,200 additional tests were conducted for
scrapie—either by third-eyelid testing or necropsy—in
response to epidemiologic suspicions of disease.
Case and Infected Flock Summary—In FY 2005, 165
newly identified infected flocks were reported, and
598 scrapie cases were confirmed and reported by the
National Veterinary Services Laboratories (NVSL) (table
6). A scrapie case is defined as an animal for which a
diagnosis of scrapie has been made by the NVSL using a
USDA-approved test (typically immunohistochemistry on
the obex or a peripheral lymph node). During FY 2005, two
scrapie cases were reported in goats. Figure 30 presents
the geographic location of U.S. mature ewe populations
(National Agricultural Statistics Service 2002 Census)
relative to flocks found to be positive for scrapie through
RSSS sampling or another regulatory or surveillance
method (denoted by NVSL-positive flocks).
40 2005 United States Animal Health Report
TABLE 6. Scrapie cases, FY 2003 through FY 2005
Number of cases
Tests or examinations FY 2003 FY 2004 FY 2005
Necropsies 315 374 461
Regulatory third-eyelid 32 20 31
RSSS 123 86 106
Total 370 480 598
1 Includes part of FY 2003 (April 1–September 30, 2003).
FIgURE 30: Distribution of mature ewe populations, by county, compared to positive flocks
(FY 2003–early FY 2006).
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Scrapie susceptibility in sheep in the United States has
been associated with two codons that encode for amino
acids in the PrP protein. These codons are at positions
136 and 171, the latter of which is thought to be the major
determinant of scrapie susceptibility in the United States.
For all the scrapie-positive sheep with known genotypes
in FY 2005, 98.4 percent were QQ at codon 171. Of these,
82.6 percent were AA at codon 136, 5.4 percent were
AV at codon 136, 0.4 percent were VV at codon 136, and
11.6 percent did not have results for codon 136. Of the
remaining 1.6 percent that were not QQ at codon 171,
0.3 percent were AAQH and 1.3 percent were AVQR at
codons 136 and 171.
Scrapie Flock Certification Program (SFCP)—The SFCP
is a cooperative effort among producers, State and Federal
animal health agencies, and industry representatives.
Through the SFCP, a flock becomes certified if, during
a 5-year monitoring period, no sheep in the flock are
diagnosed with scrapie and no clinical evidence of scrapie
is found in the flock. The program categories are described
in the following paragraphs.
Complete Monitored Category—A flock in this category
is approved to participate in the program. There are two
status levels for flocks in this category:
Enrolled flock: A flock entering the program is
assigned enrolled status and is a “complete monitored
enrolled flock.”
Certified flock: An enrolled flock that has met program
standards for 5 consecutive years advances to certified
status, meaning that it is unlikely to contain any sheep
infected with scrapie.
Selective Monitored Category—This category, though
open to any flock, was designed for producers of slaughter
lambs to allow for scrapie surveillance in large production
flocks. Only male animals over 1 year of age must have
official identification. Producers agree on the basis of
flock size to submit for scrapie diagnosis a portion of
the mature animals that are culled or die. Additionally,
an accredited veterinarian must inspect all cull ewes for
clinical signs of scrapie before slaughter. Selective status
is maintained indefinitely as long as the flock meets the
category requirements.
Trends in Plan Enrollment—Enrollment in the SFCP
has increased since 2002. As of September 30, 2005,
1,961 flocks were participating, and of these 188 were
certified flocks (table 7). One possible reason for the
increased number of certifications in 2005 was participant
awareness of standards changes, which now allow rams
from lower status flocks to be added to certified flocks
without lowering the certified flock’s status.
l
l
Challenges—For the coming year, major challenges
are to continue expanding surveillance efforts into
underrepresented areas and to increase the traceability of
sheep and goats presented for sampling. Traceability will
be enhanced by increasing compliance activities and by
improving methods for identifying and tracking sheep and
goats through review and testing of available identification
systems and integration with the National Animal
Identification System. A second tier of challenges includes
upgrading the scrapie national database, improving
field data collection by refining sample collection and
submission, and streamlining data entry and analysis.
snip...
Control and Certification Programs
Chronic Wasting Disease (CWD) in Cervids
Disease and Program History—First recognized in 1967
as a clinical “wasting” syndrome in mule deer at a wildlife
research facility in northern Colorado, CWD was identified
as a TSE in 1978. There is no known relationship between
CWD, which occurs in cervids, and any other TSE of
animals or humans.
In the mid–1980s, CWD was detected in free-ranging
deer and elk in contiguous areas of northeastern Colorado
and southeastern Wyoming. In May 1999, CWD was
found in free-ranging deer in the southwestern corner of
Nebraska (adjacent to Colorado and Wyoming) and later in
other areas in western and central Nebraska. Since 2002,
CWD has also been detected in wild deer, elk, or both
in south-central Wisconsin, southwestern South Dakota,
the western slope of the Rocky Mountains in Colorado,
southern New Mexico, northern Illinois, eastern and
central Utah, central New York, the eastern arm of West
Virginia, and northwestern Kansas. (Note: The Kansas
positive deer was harvested in late 2005, but test results
were not completed and confirmed until early 2006.)
The first infected free-ranging moose was detected in
Colorado in 2005.
49 Chapter 3: Animal Disease Eradication Programs and Control and Certification Programs
The first CWD-positive farmed elk herd in the United
States was detected in 1997 in South Dakota. Through
December 31, 2005, 31 additional CWD-positive farmed
elk herds and 8 CWD-positive farmed deer herds have
been found, for a total of 40 infected farmed cervid herds.
Current Program—APHIS–VS and State CWD surveillance
in farmed animals began in late 1997 and has increased
each year since. APHIS–VS pays laboratory costs for
all surveillance testing of farmed cervids. Responses
to onfarm CWD-positive cases include depopulation
with indemnity or quarantine. Additionally, VS conducts
traceforward and traceback epidemiologic investigations.
A proposed rule for a CWD herd-certification program for
farmed-cervid operations was published for comment in
the Federal Register on December 24, 2003. Program
goals are to control and eventually eradicate CWD from
farmed cervid herds. The program would certify herds
that demonstrate 5 years of CWD surveillance with no
evidence of disease. The proposed program requirements
include fencing, identification, inventory, and surveillance.
The rule is intended to limit interstate movement of
farmed cervids to herds enrolled in the herd-certification
program. State programs meeting or exceeding Federal
standards will be included in the Federal program. The final
rule for this program will be published and the program
implemented in 2006.
APHIS–VS has also supported CWD surveillance in wildlife
beginning in 1997. Since the national “Plan for Assisting
States, Federal Agencies, and Tribes in Managing Chronic
Wasting Disease in Wild and Captive Cervids” was
adopted in June 2002, APHIS–VS has cooperated with the
International Association of Fish and Wildlife Agencies to
promote uniform, nationwide surveillance while allowing
flexibility to meet individual State situations and needs.
Since beginning to receive line-item funding for CWD
in FY 2003, APHIS-VS has been providing assistance to
State wildlife agencies and tribes through cooperative
agreements to address the disease in free-ranging deer
and elk. This funding has covered surveillance testing
for some 90,000 hunter-killed and targeted animals in
the 2002–03 and the 2003–04 hunting seasons. Similar
numbers were projected for 2004–05 and 2005–06. All
50 States participated in the first 2 years of the program,
and 47 States requested and received funding in FY 2005.
Funding is distributed through a tiered system based on risk
of disease developed in consultation with the International
Association of Fish and Wildlife Agencies. In addition to
individual tribal assistance, an agreement with the Native
American Fish and Wildlife Society funds five regional CWD
tribal biologists to assist tribes with CWD activities.
Disease Status—In FY 2005, 15,628 farmed cervids were
tested for CWD as compared to more than 15,000 animals
in FY 2004 and more than 12,000 in FY 2003. From 1997
through 2005, CWD had been found in 32 farmed elk
herds and 8 farmed deer herds in 9 States (table 11).
Of the 40 positive herds identified as of December 31,
2005, 6 (4 in Colorado and 2 in Wisconsin) remained
under State quarantine and 33 had been depopulated.
The quarantine was lifted from one herd that underwent
rigorous surveillance for more than 5 years with no further
evidence of disease.
Challenges—The key challenges in managing CWD result
from the fact that cervids fall under multiple jurisdictions.
In 2002, at the request of Congress, an interagency group
was convened to develop a management plan to assist
States, Federal agencies, and Native American tribes in
managing CWD in captive and wild herds. Currently, this
plan is implemented by State and Federal agencies, as
budgets permit. A progress report on the implementation
of the plan was completed and presented to Congress in
May 2004.
Additional challenges are related to the difficulties
associated with testing wild cervids. High sample
throughput and more rapid test technology were needed
to meet the needs of wildlife agencies. By expanding
its contract group of State and university laboratories,
NVSL now has 26 laboratories approved to conduct CWD
testing. In addition, the Center for Veterinary Biologics has
approved four CWD antigen test kits based on enzymelinked
immunosorbent assay (ELISA), allowing faster
testing and greater throughput for surveillance testing of
wild cervids.
50 2005 United States Animal Health Report
snip...full text 120 pages ;
http://www.aphis.usda.gov/publications/animal_health/content/printable_version/2005_us_animal_health_report.pdf
PLEASE NOTE;
In cattle, BSE is one of the FAD differential diagnoses
of concern for the complaint of central nervous system
(CNS) signs, such as changes in temperament, abnormal
posture, and ataxia. In 2005, VS continued surveillance
for BSE through its Enhanced BSE Surveillance Plan
established in 2004, testing 419,268 brain submissions
and conducting
12 FAD investigations for the complaint of
CNS signs in bovines. ....
snip...FROM HOW MANY DOWNERS ???
Cattle Death Loss by Cause, 2005
Since 1990, the percentage of cattle inventory lost to all
causes has remained relatively constant at approximately
2 percent. The percentage of calf crop lost decreased
from 7.25 percent in 1990 to just over 6 percent in 2005
(fig. 27).
Cause of Loss—Predator and nonpredator cause-of-loss
estimates for cattle and calves started in 1991 and were
repeated for 1995, 2000, and 2005 as a cooperative effort
between NASS and APHIS. The most recent estimates
(2005) are presented here (fig. 28). Overall, 98.0 percent
of cattle losses and 93.3 percent of calf losses were due
to nonpredator causes. Important causes of loss for cattle
were calving problems (11.1 percent), digestive problems
(11.1 percent), and respiratory problems (24.8 percent).
The most frequently reported causes of loss for calves
were respiratory problems (31.8 percent), digestive
problems (21.2 percent), and calving problems
(17.7 percent) (fig. 29).
SNIP...CATTLE UNKNOWN CAUSE OF DEATH AT 13.3 % AND CALVES AT 11.5 %
NOW, for the rest of the story FROM ABOVE THAT ONLY ;
___12__ FAD investigations for the complaint of
CNS signs in bovines. .... WHAT A HOOT !!!
MORE FACTS BELOW AND REAL FIGURES ;
Non-Ambulatory Cattle and Calves
Released May 5, 2005, by the National Agricultural Statistics Service (NASS), Agricultural Statistics Board, U.S. Department
of Agriculture. For information on Non-ambulatory Cattle and Calves call Mike Miller at 720-3040, office hours 7:30 a.m. to
4:30 p.m. ET.
Non-Ambulatory Cattle and Calves
Non-ambulatory cattle and calves in the United States totaled 465,000 head during 2003 and
450,000 head during 2004. The number of non-ambulatory cattle 500 pounds or greater totaled
280,000 head in 2003 and 270,000 head in 2004. The number of calves under 500 pounds reported
as non-ambulatory totaled 185,000 head in 2003 and 180,000 head in 2004.
The number of operations that reported non-ambulatory cattle and calves was 103,000 in 2003 and
81,000 in 2004. In 2003, there were 66,800 beef cow operations reporting non-ambulatory cattle
and calves compared to 49,700 in 2004. There were 22,800 dairy operations reporting nonambulatory
cattle and calves in 2003 compared to 23,000 in 2004.
This report is released as a cooperative effort between the National Agricultural Statistics Service
and Animal and Plant Health Inspection Service - Veterinary Services. Data for this report were
collected on the January 1, 2004 and 2005 Cattle Surveys.
SNIP...FULL TEXT ;
http://usda.mannlib.cornell.edu/usda/current/nacac/nacac-05-05-2005.pdf
Audit Report
Animal and Plant Health Inspection Service
Bovine Spongiform Encephalopathy (BSE) Surveillance Program – Phase II
and
Food Safety and Inspection Service
Controls Over BSE Sampling, Specified Risk Materials, and Advanced Meat Recovery Products - Phase III
Report No. 50601-10-KC January 2006
Finding 2 Inherent Challenges in Identifying and Testing High-Risk Cattle Still Remain
Our prior report identified a number of inherent problems in identifying and testing high-risk cattle. We reported that the challenges in identifying the universe of high-risk cattle, as well as the need to design procedures to obtain an appropriate representation of samples, was critical to the success of the BSE surveillance program. The surveillance program was designed to target nonambulatory cattle, cattle showing signs of CNS disease (including cattle testing negative for rabies), cattle showing signs not inconsistent with BSE, and dead cattle. Although APHIS designed procedures to ensure FSIS condemned cattle were sampled and made a concerted effort for outreach to obtain targeted samples, industry practices not considered in the design of the surveillance program reduced assurance that targeted animals were tested for BSE.
In our prior report, we recommended that APHIS work with public health and State diagnostic laboratories to develop and test rabies-negative samples for BSE. This target group is important for determining the prevalence of BSE in the United States because rabies cases exhibit clinical signs not inconsistent with BSE; a negative rabies test means the cause of the clinical signs has not been diagnosed.
APHIS agreed with our recommendation and initiated an outreach program with the American Association of Veterinary Laboratory Diagnosticians, as well as State laboratories. APHIS also agreed to do ongoing monitoring to ensure samples were obtained from this target population.
Although APHIS increased the samples tested from this target group as compared to prior years, we found that conflicting APHIS instructions on the ages of cattle to test resulted in inconsistencies in what samples were submitted for BSE testing. Therefore, some laboratories did not refer their rabies negative samples to APHIS in order to maximize the number tested for this critical target population. In addition, APHIS did not monitor the number of submissions of rabies negative samples for BSE testing from specific laboratories.
According to the Procedure Manual for BSE Surveillance, dated October 2004, the target population includes:
Central nervous system (CNS) signs and/or rabies negative - sample animals of any age (emphasis added):
a. Diagnostic laboratories –samples submitted due to evidence of CNS clinical signs.
Rabies Negative Samples
USDA/OIG-A/50601-10-KC Page 19 USDA/OIG-A/50601-10-KC Page 20
b. Public health laboratories – rabies negative cases.
c. Slaughter facilities – CNS ante mortem condemned at slaughter, sampled by FSIS.
d. On-the-farm – CNS cattle that do not meet the criteria for a foreign animal disease investigation.
For FYs 2002, 2003, and 2004 (through February 2004), NVSL received 170, 133, and 45 rabies-negative samples, respectively. Between June 1, 2004, and May 29, 2005, the number of samples received for testing increased to 226 rabies suspect samples. The collection sites submitting these samples follow.
Number of Rabies
Suspect Submissions *
Slaughter Plant
0
Renderer
2
On-Farm
11
Public Health Lab
94
Diagnostic Lab
81
3D-4D
8
Other
4
Collection Site
Total
200
* 26 were tested but not counted by APHIS towards meeting the target goals because the obex was not submitted.
We obtained a copy of a memorandum, dated July 13, 2004, that APHIS sent to diagnostic and public health laboratories providing them instructions on submitting samples for cattle showing signs of CNS diseases, but testing negative for rabies. The letter was sent to about 170 State veterinary diagnostic and public health laboratories and discussed the need to submit specimens to NVSL of all adult cattle (emphasis added) that showed signs of CNS diseases, but tested negative for rabies. This directive did not specify the age of the cattle. The Procedure Manual for BSE Surveillance, dated October 2004, specified samples of cattle of any age should be submitted.
We contacted laboratories in six States to determine if it was standard procedure to submit all negative rabies samples to NVSL. We found that, because of the lack of specificity in the APHIS letter and inadequate followup by APHIS, there were inconsistencies in the age of cattle samples submitted for BSE testing. For those States contacted, the following samples were submitted versus tested as negative for rabies.
USDA/OIG-A/50601-10-KC Page 21
Rabies Negative Tests Not Sent for BSE Testing Since June 1, 2004
State
Negative Rabies Tests
Not Sent for BSE Testing
Pennsylvania a/
15
18
Kansas b/
69
16
Wisconsin c/
1
11
South Dakota d/
0
7
Arizona e/
5
0
Mississippi e/
4
0
Total
Sent for BSE Testing
33
85
12
7
5
4
146
94
52
a/ A Pennsylvania laboratory official said only rabies negative cattle over 20 months of age were submitted for BSE testing. The laboratory did not submit 18 samples for BSE testing because the animals were less than 20 months of age.
b/ Kansas laboratory officials said early in the expanded surveillance program, there was confusion as to the cattle ages that should be submitted for BSE testing. They did not know if cattle should be submitted that were above 20 months or 30 months of age. Of the 16 animals not submitted for BSE testing, 14 were under 20 months of age from early in the expanded surveillance program. The other two animals were not tested due to internal laboratory issues. The Kansas and Nebraska area office officials contacted the laboratory and told the officials to submit rabies negative cattle of any age for BSE testing. The laboratory now submits all rabies negative cattle for BSE testing.
c/ A Wisconsin laboratory official said only rabies negative cattle samples 30 months of age or older are submitted for BSE testing. Of the 11 animals not submitted for BSE testing, 8 were less than 30 months of age. Wisconsin laboratory officials were not certain why the other three samples were not submitted.
d/ Laboratory officials from South Dakota said they did not receive notification from APHIS regarding the submission of rabies negative cases for BSE testing. The section supervisor and laboratory director were not aware of any letter sent to the laboratory. The section supervisor said most bovine rabies tests at the laboratory are performed on calves. We confirmed the laboratory’s address matched the address on APHIS’ letter distribution list. However, there was no evidence that the South Dakota area office contacted the laboratory. The laboratory was not listed on the documentation from the APHIS regional office detailing the area office contacts with laboratory personnel. We contacted the South Dakota area office and were advised that while some contact had been made with the laboratory, the contact may have involved Brucellosis rather than BSE. On May 4, 2005, the area office
33 Report from the Secretary’s Advisory Committee on Foreign Animal and Poultry Diseases, February 13, 2004.
advised us they recently contacted the laboratory regarding the submission of rabies negative samples for BSE testing.
e/ Arizona and Mississippi laboratory officials said they submitted all rabies negative samples for BSE testing regardless of the age of the animal.
An NVSL official stated that APHIS is not concerned with rabies negatives samples from cattle less than 30 months of age. This position, however, is contrary to APHIS’ published target population.
Our prior audit recognized the significant challenge for APHIS to obtain samples from some high-risk populations because of the inherent problems with obtaining voluntary compliance and transporting the carcasses for testing. USDA issued rules to prohibit nonambulatory animals (downers) from entering the food supply at inspected slaughterhouses. OIG recommended, and the International Review Subcommittee33 emphasized, that USDA should take additional steps to assure that facilitated pathways exist for dead and nonambulatory cattle to allow for the collection of samples and proper disposal of carcasses. Between June 1, 2004, and May 31, 2005, the APHIS database documents 27,617 samples were collected showing a reason for submission of nonambulatory and 325,225 samples were collected with reason of submission showing "dead."
APHIS made extensive outreach efforts to notify producers and private veterinarians of the need to submit and have tested animals from these target groups. They also entered into financial arrangements with 123 renderers and other collection sites to reimburse them for costs associated with storing, transporting, and collecting samples. However, as shown in exhibit F, APHIS was not always successful in establishing agreements with non-slaughter collection sites in some States. APHIS stated that agreements do not necessarily reflect the entire universe of collection sites and that the presentation in exhibit F was incomplete because there were many collection sites without a payment involved or without a formal agreement. We note that over 90 percent of the samples collected were obtained from the 123 collection sites with agreements and; therefore, we believe agreements offer the best source to increase targeted samples in underrepresented areas.
We found that APHIS did not consider industry practices in the design of its surveillance effort to provide reasonable assurance that cattle exhibiting possible clinical signs consistent with BSE were tested. Slaughter facilities do not always accept all cattle arriving for slaughter because of their business requirements. We found that, in one State visited, slaughter facilities pre-screened and rejected cattle (sick/down/dead/others not meeting business
Downers and Cattle that Died on the Farm
USDA/OIG-A/50601-10-KC Page 22 USDA/OIG-A/50601-10-KC Page 23
34 FSIS regulations do not specifically address the designation of an establishment’s "official" boundaries; however, FSIS Notices 29-04 (dated May 27, 2004) and 40-04 (dated July 29, 2004) make it clear that FSIS inspection staff are not responsible for sampling dead cattle that are not part of the "official" premises.
35 APHIS’ area office personnel stated that it was their understanding that some establishments in the State were not presenting cattle that died or were down on the transport vehicle to FSIS for ante mortem inspection. The dead and down cattle were left in the vehicle, if possible. In rare circumstances, dead cattle may be removed from the trailer by plant personnel to facilitate the unloading of other animals.
36 A May 20, 2004, Memorandum between the Administrators of APHIS and FSIS.
standards) before presentation for slaughter in areas immediately adjacent or contiguous to the official slaughter establishment. These animals were not inspected and/or observed by either FSIS or APHIS officials located at the slaughter facilities.
FSIS procedures state that they have no authority to inspect cattle not presented for slaughter. Further, APHIS officials stated they did not believe that they had the authority to go into these sorting and/or screening areas and require that the rejected animals be provided to APHIS for BSE sampling. Neither APHIS nor FSIS had any process to assure that animals left on transport vehicles and/or rejected for slaughter arrived at a collection site for BSE testing. FSIS allows slaughter facilities to designate the area of their establishment where federal inspection is performed; this is designated as the official slaughter establishment.34
We observed animals that were down or dead in pens outside the official premises that were to be picked up by renderers. Animals that were rejected by plant personnel were transported off the premises on the same vehicles that brought them to the plant.35
A policy statement36 regarding BSE sampling of condemned cattle at slaughter plants provided that effective June 1, 2004, FSIS would collect BSE samples for testing: 1) from all cattle regardless of age condemned by FSIS upon ante mortem inspection for CNS impairment, and 2) from all cattle, with the exception of veal calves, condemned by FSIS upon ante mortem inspection for any other reason.
FSIS Notice 28-04, dated May 20, 2004, informed FSIS personnel that, "FSIS will be collecting brain samples from cattle at federally-inspected establishments for the purpose of BSE testing." The notice further states that, "Cattle off-loaded from the transport vehicle onto the premises of the federally-inspected establishment (emphasis added), whether dead or alive, will be sampled by the FSIS Public Health Veterinarian (PHV) for BSE after the cattle have been condemned during ante mortem inspection. In addition, cattle passing ante mortem inspection but later found dead prior to slaughter will be condemned and be sampled by the FSIS PHV."
USDA/OIG-A/50601-10-KC Page 24
37 FSIS Notice 40-04, dated July 29, 2004.
38 FSIS Notice 29-04, dated May 27, 2004.
APHIS has the responsibility for sampling dead cattle off-loaded onto plant-owned property that is adjoining to, but not considered part of, the "official premises.37 FSIS procedures38 provide that "Dead cattle that are off-loaded to facilitate the off-loading of live animals, but that will be re-loaded onto the transport vehicle, are not subject to sampling by FSIS.
While performing our review in one State, we reviewed the circumstances at two slaughter facilities in the State that inspected and rejected unsuitable cattle before the animals entered the official receiving areas of the plants. This pre-screening activity was conducted in areas not designated by the facility as official premises of the establishment and not under the review or supervision of FSIS inspectors. The plant rejected all nonambulatory and dead/dying/sick animals delivered to the establishment. Plant personnel refused to offload any dead or downer animals to facilitate the offloading of ambulatory animals. Plant personnel said that the driver was responsible for ensuring nonambulatory animals were humanely euthanized and disposing of the carcasses of the dead animals. Plant personnel informed us that they did not want to jeopardize contracts with business partners by allowing unsuitable animals on their slaughter premises.
In the second case, one family member owned a slaughter facility while another operated a livestock sale barn adjacent to the slaughter facility. The slaughter facility was under FSIS’ supervision while the sale barn was not. Cattle sometimes arrived at the sale barn that were sick/down/dead or would die or go down while at the sale barn. According to personnel at the sale barn, these animals were left for the renderer to collect. The healthy ambulatory animals that remained were marketed to many buyers including the adjacent slaughter facility. When the slaughter facility was ready to accept the ambulatory animals for processing, the cattle would be moved from the sale barn to the slaughter facility where they were subject to FSIS’ inspection.
We requested the slaughter facilities to estimate the number of cattle rejected on a daily basis (there were no records to confirm the estimates). We visited a renderer in the area and found that the renderer had a contract with APHIS to collect samples for BSE testing. In this case, although we could not obtain assurance that all rejected cattle were sampled, the renderer processed a significant number of animals, as compared to the slaughter plants’ estimates of those rejected. Due to the close proximity (less than 5 miles) of the renderer to the slaughter facilities, and the premium it paid for dead cattle that were in good condition, there was a financial incentive for transport drivers to dispose of their dead animals at this renderer.
USDA/OIG-A/50601-10-KC Page 25
In our discussions with APHIS officials in Wisconsin and Iowa, they confirmed that there were plants in their States that also used pre-screening practices. On May 27, 2005, we requested APHIS and FSIS to provide a list of all slaughter facilities that pre-screened cattle for slaughter in locations away from the area designated as the official slaughter facility. Along with this request, we asked for information to demonstrate that either APHIS or FSIS confirmed there was a high likelihood that high-risk animals were sampled at other collection sites.
In response to our request, the APHIS BSE Program Manager stated that APHIS did not have information on slaughter plants that pre-screen or screen their animals for slaughter suitability off their official plant premises. To their knowledge, every company or producer that submits animals for slaughter pre-sorts or screens them for suitability at various locations away from the slaughter facility. For this reason, USDA focused its BSE sample collection efforts at other types of facilities such as renderers, pet food companies, landfills, and dead stock haulers. Further, in a letter to OIG on June 14, 2005, the administrators of APHIS and FSIS noted the following:
"…we believe that no specific actions are necessary or appropriate to obtain reasonable assurance that animals not presented for slaughter are being tested for BSE. There are several reasons for our position. First, we do not believe that the practice is in fact causing us to not test a significant enough number of animals in our enhanced surveillance program to invalidate the overall results. Second, OIG has concluded that because of the geographical proximity and business relationships of the various entities involved in the case investigated, there is reasonable assurance that a majority of the rejected cattle had been sampled. Third, it is also important to remember that the goal of the enhanced surveillance program is to test a sufficient number of animals to allow us to draw conclusions about the level of BSE (if any) in the American herd…We believe that the number we may be not testing because of the "pre-sorting" practice does not rise to a significant level. The number of animals tested to date has far exceeded expectations, so it is reasonable to infer that there are few of the animals in question, or that we are testing them at some other point in the process…APHIS estimated…there were approximately 446,000 high risk cattle…[and APHIS has]…tested over 375,000 animals in less than 1 year. This indicated that we are missing few animals in the high-risk population, including those that might be pre-sorted before entering a slaughter facility’s property."
We obtained 123 APHIS sampling agreements and contracts with firms and plotted their locations within the United States (see exhibit F). We also analyzed the samples tested to the BSE sampling goals allocated to each State under the prior surveillance program. This analysis showed that there are
USDA/OIG-A/50601-10-KC Page 26
39APHIS noted that sites with agreements do not necessarily reflect the entire universe of collection sites and at some sites APHIS collects samples with no payment involved and no agreement in place. OIG agrees that not all collection sites are reflected in our presentation of the 123 sites with reimbursable agreements. OIG believes obtaining sampling agreements is one of the primary methods available to increase sample numbers in areas with sampling gaps.
sampling gaps in two large areas of the United States where APHIS did not have contracts with collection sites. These two areas are shown in the following chart (Montana, South Dakota, North Dakota and Wyoming – Group 1 and Louisiana, Oklahoma, Arkansas, and Tennessee – Group 2):
State
Original Sampling Goal Based on (268,500 sampling goal)
Samples collected as of May 31, 2005
No. of BSE Sampling Agreements/
Contracts39
MT
5,076
4,894
2
SD
6,938
4,146
1
ND
3,616
3,442
0
WY
2,513
2,452
0
AREA TOTAL
14,934
OK
7,792
5,385
1
AR
3,672
3,319
0
TN
4,938
1,888
1
LA
2,312
1,860
1
AREA TOTAL
Deficit
182
2,792
174
61
2,407
353
3,050
452
12,452
APHIS notes that for the current surveillance program, it had established regional goals and APHIS was not trying to meet particular sampling levels in particular States. However, we believe that it would be advantageous for APHIS to monitor collection data and increase outreach when large geographical areas such as the above States do not provide samples in proportion to the numbers and types of cattle in the population.
We also disagree with APHIS/FSIS’ contention that because they have tested over 375,000 of their 446,000 estimate of high risk cattle, few in the high-risk population are being missed, including those that might be pre-screened before entering a slaughter facility’s property. In our prior audit, we reported that APHIS underestimated the high-risk population; we found that this estimate should have been closer to 1 million animals (see Finding 1). We recognize that BSE samples are provided on a voluntary basis; however, APHIS should consider industry practice in any further maintenance surveillance effort. Animals unsuitable for slaughter exhibiting symptoms not inconsistent with BSE should be sampled and their clinical signs recorded. However, this cited industry practice results in rejected animals not being made available to either APHIS or FSIS veterinarians for their observation and identification of clinical signs exhibited ante mortem. Although these animals may be sampled later at other collection sites, the animals are provided post mortem without information as to relevant clinical signs exhibited ante mortem. For these reasons, we believe APHIS needs to
USDA/OIG-A/50601-10-KC Page 27
observe these animals ante mortem when possible to assure the animals from the target population are ultimately sampled and the clinical signs evaluated.
snip...
http://www.usda.gov/oig/webdocs/50601-10-KC.pdf
USDA Testing Protocols and Quality Assurance Procedures
In November 2004, USDA announced that its rapid screening test produced an inconclusive BSE test result. A contract laboratory ran its rapid screening test on a brain sample collected for testing and produced three high positive reactive results. As required, the contract laboratory forwarded the inconclusive sample to APHIS’ National Veterinary Services Laboratories (NVSL) for confirmation. NVSL repeated the rapid screening test, which again produced three high positive reactive results. Following established protocol, NVSL ran its confirmatory test, an immunohistochemistry (IHC) test, which was interpreted as negative for BSE.
Faced with conflicting results between the rapid screening and IHC tests, NVSL scientists recommended additional testing to resolve the discrepancy but APHIS headquarters officials concluded that no further testing was necessary since testing protocols were followed and the confirmatory test was negative. In our discussions with APHIS officials, they justified their decision to not do additional testing because the IHC test is internationally recognized as the "gold standard" of testing. Also, they believed that
USDA/OIG-A/50601-10-KC/ Page iv
conducting additional tests would undermine confidence in USDA’s testing protocols.
OIG obtained evidence that indicated additional testing was prudent. We came to this conclusion because the rapid screening tests produced six high positive reactive results, the IHC tests conflicted, and various standard operating procedures were not followed. Also, our review of the relevant scientific literature, other countries’ protocols, and discussions with experts led us to conclude that additional confirmatory testing should be considered in the event of conflicting test results.
To maintain objectivity and independence, we requested that USDA’s Agricultural Research Service (ARS) perform the Office International des Epizooties (OIE) Scrapie-Associated Fibrils (SAF) immunoblot test. The additional testing produced positive results. To confirm, the Secretary of Agriculture requested that an internationally recognized BSE laboratory in Weybridge, England (Weybridge) perform additional testing. Weybridge conducted various tests, including their own IHC tests and three Western blot tests. The tests confirmed that the cow was infected with BSE. The Secretary immediately directed USDA scientists to work with international experts to develop new protocols that include performing dual confirmatory tests in the event of an inconclusive BSE screening test.
We attribute the failure to identify the BSE positive sample to rigid protocols, as well as the lack of adequate quality assurance controls over its testing program. Details of our concerns are discussed in Findings 3 and 4.
snip...
Section 2. Testing Protocols and Quality Assurance Controls In November 2004, USDA announced that its rapid screening test, Bio-Rad Enzyme Linked Immunosorbent Assay (ELISA), produced an inconclusive BSE test result as part of its enhanced BSE surveillance program. The ELISA rapid screening test performed at a BSE contract laboratory produced three high positive reactive results.40 As required,41 the contract laboratory forwarded the inconclusive sample to the APHIS National Veterinary Services Laboratories (NVSL) for confirmatory testing. NVSL repeated the ELISA testing and again produced three high positive reactive results.42 In accordance with its established protocol, NVSL ran its confirmatory test, an immunohistochemistry (IHC) test, which was interpreted as negative for BSE. In addition, NVSL performed a histological43 examination of the tissue and did not detect lesions44 consistent with BSE. Faced with conflicting results, NVSL scientists recommended additional testing to resolve the discrepancy but APHIS headquarters officials concluded no further testing was necessary because testing protocols were followed. In our discussions with APHIS officials, they justified their decision not to do additional testing because the IHC is internationally recognized as the “gold standard.” Also, they believed that conducting additional tests would undermine confidence in USDA’s established testing protocols. However, OIG obtained evidence that indicated additional testing was prudent to ensure that USDA’s testing protocols were effective in detecting BSE and that confidence in USDA’s testing procedures was maintained. OIG came to this conclusion because the rapid tests produced six high positive reactive results, confirmatory testing conflicted with the rapid test results, and various standard operating procedures were not followed. Also, our review of scientific literature, other country protocols, as well as discussions with internationally recognized experts led us to conclude that confirmatory testing should not be limited when conflicting test results are obtained. To maintain objectivity and independence in our assessment, we requested the USDA Agricultural Research Service (ARS) perform the Office International des Epizooties (OIE) Scrapie-Associated Fibrils (SAF) 40 ELISA test procedures require two additional (duplicate) tests if the initial test is reactive, before final interpretation. If either of the duplicate tests is reactive, the test is deemed inconclusive. 41 Protocol for BSE Contract Laboratories to Receive and Test Bovine Brain Samples and Report Results for BSE Surveillance Standard Operating Procedure (SOP), dated October 26, 2004. 42 The NVSL conducted an ELISA test on the original material tested at the contract laboratory and on two new cuts from the sample tissue. 43 A visual examination of brain tissue by a microscope. 44 A localized pathological change in a bodily organ or tissue.
immunoblot.45 ARS performed the test at the National Animal Disease Center because NVSL did not have the necessary equipment46 (ultracentrifuge) to do the test. APHIS scientists observed and participated, as appropriate, in this effort. The additional tests conducted by ARS produced positive results. To confirm this finding, the Secretary requested the internationally recognized BSE reference laboratory in Weybridge, England, (Weybridge) to perform additional confirmatory testing. Weybridge conducted various tests, including their own IHC methods, as well as three Western blot methods. The tests confirmed that the suspect cow was infected with BSE. Also, Weybridge confirmed this case as an unequivocal positive case of BSE on the basis of IHC. As a result of this finding, the Secretary immediately directed USDA scientists to work with international experts to develop a new protocol that includes performing dual confirmatory tests in the event of another inconclusive BSE screening test. Finding 3 Rigid Protocols Reduced the Likelihood BSE Could be Detected APHIS relied on a single test method, as well as a histological examination of tissue for lesions consistent with BSE, to confirm the presence of BSE even though discrepant test results indicated further testing may be prudent. When IHC test results were interpreted as negative, APHIS concluded the sample tested negative for BSE. Subsequent independent tests initiated by OIG using a different testing method, as well as confirmatory testing by Weybridge, determined that the suspect sample was a positive case of BSE. APHIS Declares BSE Sample Negative Despite Conflicting Results When the tissue sample originally arrived at NVSL in November 2004 from the contract lab, NVSL scientists repeated the ELISA screening test and again produced three high positive reactive results. NVSL scientists cut out two sections of the brain sample for IHC testing. One section was used for an experimental procedure that was not part of the confirmatory testing protocol, and the other cut was for normal IHC testing using scrapie for a positive control.47 According to NVSL scientists, the experimental test results were inconclusive but the IHC test was interpreted as negative. The NVSL scientists were concerned with the inconsistencies and conducted 45 The OIE SAF immunoblot is an internationally recognized confirmatory test, often referred to as a Western blot test. There are different types of Western blots; the OIE SAF immunoblot includes enrichment steps taken with the sample prior to the standard Western blot steps. 46 APHIS has now ordered the necessary equipment for NVSL. USDA/OIG-A/50601-10-KC Page 32
47 A positive control is a sample that is known to contain a given disease or react in the test. The sample then can be used to make sure that the test for that disease works properly. In the case of BSE, tissue infected with either scrapie or BSE can serve as a positive control for an IHC test for BSE since both are different forms of the same disease (transmissible spongiform encephalopathy or TSE).
another IHC test using BSE as a positive control.48 The test result was also interpreted as negative. Also, according to the NVSL scientists, the histological examination of the tissue did not detect lesions consistent with BSE. After the second negative IHC test, NVSL scientists supported doing additional testing. They prepared a plan for additional tests; if those tests had been conducted, BSE may have been detected in the sample. The additional tests recommended by NVSL scientists, but not approved by APHIS Headquarters officials, were the IHC using other antibodies (IHC testing using different antibodies ultimately produced positive results); IHC testing of additional regions of the brain (the cerebellum tested positive); regular and enriched (OIE-like) Western blots (the obex and cerebellum tested positive); and variable rapid tests (the obex and cerebellum tested positive with two different rapid tests). NVSL officials also recommended that the sample be sent to Weybridge for confirmatory testing (to conduct IHC and OIE Western blot tests). In June 2005, Weybridge conducted IHC testing with three different antibodies, including the antibody used in the United States (tested positive), the OIE Western blot (tested positive), a modified commercial kit Western blot (negative) and the NaPTA49 Western blot (tested positive). We obtained information as to the differing protocols used by other countries. We found that while APHIS determined that additional testing was unnecessary after the IHC test, other countries have used multiple tests to confirm positives. In Japan, for example, all reactive screening test samples are examined by both IHC and a Western blot (different from the OIE SAF immunoblot). In the United Kingdom (U.K.), IHC and Western blot (different from the OIE SAF immunoblot) tests are used for all animals that test positive with a screening test. When IHC and the Western blot fail to confirm a positive rapid test, the U.K. resorts to a third test, the OIE SAF immunoblot. With these procedures in place, both Japan and the U.K. have found BSE cases that were rapid test reactive, IHC negative, and finally confirmed positive with a Western blot. Evidence Indicated Additional Testing Would Be Prudent We also spoke with an internationally recognized BSE expert regarding the advisability of limiting confirmatory testing when conflicting results are obtained. This official expressed concern about limiting confirmatory tests to the IHC despite its status as one of the “gold standard” tests. He advised that the IHC is not one test; it is a test method that can vary significantly in sensitivity from laboratory to laboratory. New antibodies can improve or
USDA/OIG-A/50601-10-KC Page 33
48 The NVSL uses scrapie as the positive control as part of its normal IHC testing procedures. Due to the conflicting results between the ELISA and IHC tests, the NVSL conducted another IHC test with BSE as the positive control. Subsequently, the NVSL modified the Confirming Inconclusive Results from BSE Testing Laboratories at the NVSL SOP to show that all IHC tested BSE inconclusive samples from contract laboratories will use BSE as the positive control. 49 Sodium phosphotungstic acid.
USDA/OIG-A/50601-10-KC Page 34
reduce sensitivity, as can variations in many of the reagents50 used. He explained that his laboratory had experienced cases where an initial confirmatory IHC test was challenged by either a more extensive IHC test or “…applying a more sensitive immunoblot.” He emphasized the importance of having additional confirmatory testing to resolve discrepant results since there are many variables, and most of the variability appears to be due to test performance of the laboratory. OIG became concerned that APHIS relied on its confirmatory test methods when rapid sc
Date: October 13, 2006 at 11:25 am PST
2005 UNITED STATES ANIMAL HEALTH REPORT
snip...
BSE Surveillance
Since 1990, the U.S. Department of Agriculture (USDA)
has taken aggressive measures to prevent the introduction
and potential spread of BSE. Following confirmation
of BSE in an imported cow in December 2003, USDA
designed and implemented an Enhanced BSE Surveillance
Program to more accurately determine the level of disease
present in the U.S. cattle population.
The Enhanced BSE Surveillance Program tested as many
cattle as possible in the targeted high-risk population
beginning June 1, 2004. Collection at an enhanced level
has continued beyond 18 months to ameliorate concerns
of trading partners. Experience in the United Kingdom
and Europe has shown that, if present, BSE is most likely
to be detected in adult cattle exhibiting clinical signs
consistent with the disease.
In general, the highest risk categories are adult cattle
showing clinical signs involving the central nervous
system (CNS) and dead and nonambulatory cattle with
clinical signs that could not be adequately evaluated. This
population was estimated to total 445,886 adult cattle per
year in the United States. This number was derived in part
from National Animal Health Monitoring System (NAHMS)
surveys of livestock producers and other estimates.
This estimate includes adult cattle in the following
categories:
Condemned at slaughter for CNS signs;
Moribund, dead, injured, or emaciated (FSIS data
2002);
CNS abnormalities reported for FAD investigations
(APHIS data 2003);
Died onfarm of unknown causes;
Lameness or injury that resulted in euthanasia; and
Cattle that died with signs of incoordination or severe
depression.
The sampling strategy was designed to target animals in
these categories.
Between June 1, 2004, and March 17, 2006, BSE samples
were collected from 5,776 unique locations across the
United States. These locations included slaughter plants,
renderers, farms, public health laboratories, veterinary
diagnostic laboratories, and salvage slaughter (3D–4D)1
plants.
To determine the extent to which the U.S. surveillance is
consistent with OIE guidelines, we have evaluated and
classified surveillance data over the past 7 years according
to OIE standards (table 5).
In May 2005, the OIE general Assembly approved a
new chapter and appendix for BSE surveillance. This
approach assigned point values to each sample, based on
animal age and the subpopulation it was from, and the
likelihood of detecting infected cattle of that age in that
subpopulation. (Prior to May 2005, OIE had recommended
a surveillance level based on the size of the adult cattle
population—for the United States that number was 433
samples with clinical signs consistent with BSE per year.)
Sample values were classified in the OIE system as
belonging to four surveillance strata (streams): clinical
suspect, casualty slaughter, fallen stock, and healthy
slaughter. Samples were also stratified by age.
Cattle were categorized in the clinical suspect stream
if they were submitted under the submission types of
highly suspicious for BSE, rabies suspects, CNS signs,
or antemortem-condemned by FSIS with condemnation
codes for CNS signs or rabies. In addition, many samples
with a clinical history of signs likely to be associated with
BSE were submitted in other categories. Many of these
represented valuable samples, but the OIE definition of
“clinical suspect” did not readily differentiate them from
animals with other clinical signs compatible with BSE.
Some of these cattle were subsequently categorized as
clinical suspects by comparing the likelihood of finding
the signs in histopathologically confirmed cases reported
in the United Kingdom2 with the likelihood of finding
the signs in uninfected animals from the enhancedsurveillance
targeted population. For example, if a sign or
combination of signs were found 30 percent of the time
in BSE cases but only once in every 1,000 uninfected
animals (0.1 percent), then it would be 0.30/0.001 = 300
times more likely to occur in the cases (likelihood ratio =
300 in this case). A likelihood ratio threshold of 807 was
established as a cutoff value for determination of clinical
suspects. This threshold was estimated using input data
from the United Kingdom in the BSurvE3 model, which
provided the average (expected) value for the ratio of
probability of an infected animal showing clinical signs
to an uninfected animal showing clinical signs. Thus, if a
sample was submitted from an animal with combinations
of clinical signs at least 807 times more likely to have
been seen in BSE cases than in the U.S. high-risk
population, it was classified as a clinical suspect.
Cattle with likelihood ratios below the threshold were
allocated into surveillance streams according to the
animal’s submission type as follows:
Submission types of “Nonambulatory” were classified
in the “casualty slaughter” stream;
Submission types of “Other clinical signs that may be
associated with BSE” were classified in the “casualty
slaughter” stream;
Submission types of “FSIS antemortem condemned”
were classified in the “casualty slaughter” stream as
long as the condemnation reason was not “dead”;
Submission types of “FSIS antemortem condemned”
with a condemnation code of “dead” were classified in
the “fallen stock” stream;
Submission types of “dead” were classified in the
“fallen stock” stream;
Submission types of “apparently healthy” were
classified in the “healthy slaughter” stream.
BSE surveillance samples from 1999 through 2003
were collected before the OIE surveillance streams
were established in 2005 and were not submitted with
the same clinical history as that used for the enhanced
surveillance in 2004–05. In order to apply the OIE point
tables, data about these samples were requested from
the National Veterinary Services Laboratories (NVSL) and
were sorted by Centers for Epidemiology and Animal
Health (CEAH) epidemiologists based on the history
included with the sample.
This information is excerpted from the report Summary
of BSE Surveillance in the United States accessed and
available on the Web as of May 2, 2006, at
aphis.usda.gov/newsroom/hot_issues/bse/content/
printable_version/SummaryEnhancedBSE-Surv4-26-
06.pdf>. Details on the Enhanced BSE Surveillance
Program are posted at
issues/bse/BSEOIg.pdf>.
2 Wilesmith, J. W.; Ryan, J. B.; Hueston, W. D. 1992. Bovine spongiform
encephalopathy: case-control studies of calf feeding practices and
meat and bonemeal inclusion in proprietary concentrates. Research in
Veterinary Science 52(3): 325–331.
3 Available, as of April 20, 2006, at . The
BSurvE tool is a Microsoft Excel™ spreadsheet application designed to
estimate BSE prevalence based on targeted sampling strategies.
35 Chapter 2: National Animal Health Surveillance System (NAHSS)
TABLE 5: OIE points from BSE surveillance in the U.S. accumulated for 7 years
Year of testing1
Total
samples2
Clinical
suspects
Fallen
stock
Casualty
slaughter
Healthy
slaughter OIE points3
10/1/05 to 03/17/064 181,564 438 142,337 18,991 19,798 285,491
FY5 2005 413,647 1,527 361,557 50,557 6 899,642
FY 2004 90,085 1,066 62,054 25,096 1,869 592,369
FY 2003 20,778 577 3,106 16,613 482 267,480
FY 2002 20,380 569 2,818 16,045 948 251,740
FY 2001 5,340 665 1 4,515 159 299,177
FY 2000 2,753 664 0 2,064 25 266,891
4/1/99 to 9/30/996 666 265 15 351 35 111,014
Total surveillance
(including enhanced surveillance)
7735,213 5,771 571,888 134,232 23,322 2,973,804
Total for enhanced surveillance only
6/1/04 to 3/17/06
667,767 2,602 559,546 84,534 21,085 1,583,127
1 Testing includes the most recent 7 years of data collected from Apr. 1, 1999, through March 17, 2006.
2 Number of samples and clinical suspects represents animals eligible for surveillance according to the Terrestrial Animal Health Code Article 3.8.4.
3 Note: Animals counted as eligible for OIE points included animals older than 1 year according to the OIE point allocation table. Removal of points from the “juvenile”
category of the OIE points table would decrease the total by 2,843 points. Other documents showing U.S. data may vary due to inclusion or exclusion of young animals.
4 Includes 6 months of fiscal year 2006.
5 The U.S. Government’s fiscal year extends from October 1 through September 30 (e.g., FY 2005 began on 10/1/2004 and ended on 9/30/2005).
6 Includes 6 months of FY 1999.
7 Total includes two positive indigenous animals and one positive animal imported from Canada.
1 3D–4D facilities are slaughter facilities that salvage meat from dead,
dying, disabled, or diseased animals, the meat from which would not
likely pass inspection for human consumption (i.e., edible meat). Much
of this meat goes into either pet food or rendering.
34 2005 United States Animal Health Report
Scrapie Surveillance Evaluation
In general, evaluating a surveillance program entails a
systematic review to assess the degree to which the
program fulfills its stated objectives and meets accepted
surveillance standards. Program strengths and areas for
improvement are identified, and the program’s ability to
adapt to changing situations is evaluated. Evaluating the
surveillance component of one VS program disease was
identified as a key action item in the NAHSS strategic
plan (see
nahss/NAHSS_Strategic_Plan_2005_0216.pdf>).
The surveillance component of the VS scrapie
program was chosen for evaluation. Led by the NSU,
an interdisciplinary working group was developed
consisting of an economist, statistician, several veterinary
epidemiologists, and an industry representative.
The evaluation process focused on four main areas:
surveillance structures (organization and communication),
surveillance processes (data collection, data analysis and
interpretation, and dissemination of results), qualitative
attributes (i.e., simplicity, flexibility, acceptability), and
resource distribution and utilization. Characteristics of the
system were compared with the draft VS Surveillance
Standards, as noted throughout the evaluation.
The evaluation and data gathered focused primarily on the
Regulatory Scrapie Slaughter Surveillance Program testing
and other nonslaughter surveillance testing in sheep
implemented since 2001. Although most of the evaluation
results should be applicable to scrapie surveillance in
goats, this component was not specifically evaluated.
Phone interviews were conducted with State and/or VS
field personnel involved in scrapie surveillance activities
in nine different States representing both APHIS’ Eastern
and Western Regions. Questions addressed the general
objectives, importance, and efficiency of the program; the
communication within the program; and the acceptability,
compliance, and coverage of the program. Personnel
interviewed were assured anonymity.
The evaluation report has been completed and delivered
to VS’ National Center for Animal Health Programs.
snip...
CHAPTER 3
Animal Disease Eradication Programs and Control and Certification Programs
The following Veterinary Services (VS) programs are
designed to eradicate, control, or prevent diseases that
threaten the biological and commercial health of the U.S.
livestock and poultry industries.
Eradication Programs
VS eradication programs include scrapie in sheep and
goats, tuberculosis in cattle and cervids, pseudorabies and
brucellosis in swine, and brucellosis in cattle and bison.
Scrapie in Sheep and Goats
Disease and Program History—Scrapie was first
discovered in the United States in 1947 in a Michigan
flock that, for several years, had imported sheep of
British origin from Canada. Since 1952, VS has worked
to control scrapie in the United States. As a result of
increasing industry and public concern about transmissible
spongiform encephalopathies (TSEs) and the discovery of
new TSE diagnostic and control methods, VS initiated an
accelerated scrapie eradication program in 2000.
Current Program—The primary aspects of the scrapie
eradication program are animal identification, surveillance,
tracing of positive and exposed animals, testing of sheep
and goats in exposed flocks, cleanup of infected flocks,
and certification of flocks.
Animal Identification—Identification of breeding
sheep and culled breeding sheep is mandatory when
ownership changes. The only sheep that do not have to
be identified are those less than 18 months old and, in
the case of ewes, those that also have not lambed or
become pregnant and are in slaughter channels. As of
September 30, 2005, 103,580 premises with sheep and/or
goats were recorded in the scrapie national database. (In
this database, a premises that contains both sheep and
goats might be listed once for each species.) Of these
premises, 73,807 have requested and received official
eartags (tags approved for use by the Animal and Plant
Health Inspection Service [APHIS] in the official scrapie
eradication program).
Regulatory Scrapie Slaughter Surveillance (RSSS)—
The RSSS program, initiated on April 1, 2003, is the
primary surveillance method for scrapie in the United
States. RSSS identifies scrapie-infected flocks through
targeted slaughter surveillance of sheep and goat
populations that have been recognized as having higherthan-
average scrapie prevalence. These are defined as
mature black- or mottle-faced sheep and any mature
sheep or goats showing clinical signs that could be
associated with scrapie, such as poor body condition,
wool loss, or gait abnormalities. Only sheep with some
form of identification (e.g., such as United States
Department of Agriculture [USDA]-approved eartags,
electronic ID, backtags, and tattoos or lot identification)
are sampled. This arrangement allows for tracing positive
animals back to the farm of origin.
During FY 2005, as part of the RSSS program, 30,247
sheep and goat samples, collected from 78 slaughter
plants in 24 States, were tested for scrapie using
immunohistochemistry on brain or lymphoid tissue, or
both. Of the 106 animals diagnosed as positive for scrapie,
93 were black-faced, 11 were mottle-faced, 1 was whitefaced,
and 1 was unknown.
Under the scrapie program, positive test results are traced
back to the animal’s flock of origin, and the flock is placed
under movement restrictions until all high-risk animals
(genetically susceptible females) are removed. High-risk
animals that had been moved from these flocks before
being placed under movement restrictions are traced and
tested.
Testing Summary—In response to epidemiologic
suspicions of disease, field Veterinary Medical Officers
conduct testing to determine if scrapie is present. Such
cases are known as regulatory field cases. In addition to
the 30,247 samples tested under the RSSS program in
2005, about 5,200 additional tests were conducted for
scrapie—either by third-eyelid testing or necropsy—in
response to epidemiologic suspicions of disease.
Case and Infected Flock Summary—In FY 2005, 165
newly identified infected flocks were reported, and
598 scrapie cases were confirmed and reported by the
National Veterinary Services Laboratories (NVSL) (table
6). A scrapie case is defined as an animal for which a
diagnosis of scrapie has been made by the NVSL using a
USDA-approved test (typically immunohistochemistry on
the obex or a peripheral lymph node). During FY 2005, two
scrapie cases were reported in goats. Figure 30 presents
the geographic location of U.S. mature ewe populations
(National Agricultural Statistics Service 2002 Census)
relative to flocks found to be positive for scrapie through
RSSS sampling or another regulatory or surveillance
method (denoted by NVSL-positive flocks).
40 2005 United States Animal Health Report
TABLE 6. Scrapie cases, FY 2003 through FY 2005
Number of cases
Tests or examinations FY 2003 FY 2004 FY 2005
Necropsies 315 374 461
Regulatory third-eyelid 32 20 31
RSSS 123 86 106
Total 370 480 598
1 Includes part of FY 2003 (April 1–September 30, 2003).
FIgURE 30: Distribution of mature ewe populations, by county, compared to positive flocks
(FY 2003–early FY 2006).
snip...
Scrapie susceptibility in sheep in the United States has
been associated with two codons that encode for amino
acids in the PrP protein. These codons are at positions
136 and 171, the latter of which is thought to be the major
determinant of scrapie susceptibility in the United States.
For all the scrapie-positive sheep with known genotypes
in FY 2005, 98.4 percent were QQ at codon 171. Of these,
82.6 percent were AA at codon 136, 5.4 percent were
AV at codon 136, 0.4 percent were VV at codon 136, and
11.6 percent did not have results for codon 136. Of the
remaining 1.6 percent that were not QQ at codon 171,
0.3 percent were AAQH and 1.3 percent were AVQR at
codons 136 and 171.
Scrapie Flock Certification Program (SFCP)—The SFCP
is a cooperative effort among producers, State and Federal
animal health agencies, and industry representatives.
Through the SFCP, a flock becomes certified if, during
a 5-year monitoring period, no sheep in the flock are
diagnosed with scrapie and no clinical evidence of scrapie
is found in the flock. The program categories are described
in the following paragraphs.
Complete Monitored Category—A flock in this category
is approved to participate in the program. There are two
status levels for flocks in this category:
Enrolled flock: A flock entering the program is
assigned enrolled status and is a “complete monitored
enrolled flock.”
Certified flock: An enrolled flock that has met program
standards for 5 consecutive years advances to certified
status, meaning that it is unlikely to contain any sheep
infected with scrapie.
Selective Monitored Category—This category, though
open to any flock, was designed for producers of slaughter
lambs to allow for scrapie surveillance in large production
flocks. Only male animals over 1 year of age must have
official identification. Producers agree on the basis of
flock size to submit for scrapie diagnosis a portion of
the mature animals that are culled or die. Additionally,
an accredited veterinarian must inspect all cull ewes for
clinical signs of scrapie before slaughter. Selective status
is maintained indefinitely as long as the flock meets the
category requirements.
Trends in Plan Enrollment—Enrollment in the SFCP
has increased since 2002. As of September 30, 2005,
1,961 flocks were participating, and of these 188 were
certified flocks (table 7). One possible reason for the
increased number of certifications in 2005 was participant
awareness of standards changes, which now allow rams
from lower status flocks to be added to certified flocks
without lowering the certified flock’s status.
l
l
Challenges—For the coming year, major challenges
are to continue expanding surveillance efforts into
underrepresented areas and to increase the traceability of
sheep and goats presented for sampling. Traceability will
be enhanced by increasing compliance activities and by
improving methods for identifying and tracking sheep and
goats through review and testing of available identification
systems and integration with the National Animal
Identification System. A second tier of challenges includes
upgrading the scrapie national database, improving
field data collection by refining sample collection and
submission, and streamlining data entry and analysis.
snip...
Control and Certification Programs
Chronic Wasting Disease (CWD) in Cervids
Disease and Program History—First recognized in 1967
as a clinical “wasting” syndrome in mule deer at a wildlife
research facility in northern Colorado, CWD was identified
as a TSE in 1978. There is no known relationship between
CWD, which occurs in cervids, and any other TSE of
animals or humans.
In the mid–1980s, CWD was detected in free-ranging
deer and elk in contiguous areas of northeastern Colorado
and southeastern Wyoming. In May 1999, CWD was
found in free-ranging deer in the southwestern corner of
Nebraska (adjacent to Colorado and Wyoming) and later in
other areas in western and central Nebraska. Since 2002,
CWD has also been detected in wild deer, elk, or both
in south-central Wisconsin, southwestern South Dakota,
the western slope of the Rocky Mountains in Colorado,
southern New Mexico, northern Illinois, eastern and
central Utah, central New York, the eastern arm of West
Virginia, and northwestern Kansas. (Note: The Kansas
positive deer was harvested in late 2005, but test results
were not completed and confirmed until early 2006.)
The first infected free-ranging moose was detected in
Colorado in 2005.
49 Chapter 3: Animal Disease Eradication Programs and Control and Certification Programs
The first CWD-positive farmed elk herd in the United
States was detected in 1997 in South Dakota. Through
December 31, 2005, 31 additional CWD-positive farmed
elk herds and 8 CWD-positive farmed deer herds have
been found, for a total of 40 infected farmed cervid herds.
Current Program—APHIS–VS and State CWD surveillance
in farmed animals began in late 1997 and has increased
each year since. APHIS–VS pays laboratory costs for
all surveillance testing of farmed cervids. Responses
to onfarm CWD-positive cases include depopulation
with indemnity or quarantine. Additionally, VS conducts
traceforward and traceback epidemiologic investigations.
A proposed rule for a CWD herd-certification program for
farmed-cervid operations was published for comment in
the Federal Register on December 24, 2003. Program
goals are to control and eventually eradicate CWD from
farmed cervid herds. The program would certify herds
that demonstrate 5 years of CWD surveillance with no
evidence of disease. The proposed program requirements
include fencing, identification, inventory, and surveillance.
The rule is intended to limit interstate movement of
farmed cervids to herds enrolled in the herd-certification
program. State programs meeting or exceeding Federal
standards will be included in the Federal program. The final
rule for this program will be published and the program
implemented in 2006.
APHIS–VS has also supported CWD surveillance in wildlife
beginning in 1997. Since the national “Plan for Assisting
States, Federal Agencies, and Tribes in Managing Chronic
Wasting Disease in Wild and Captive Cervids” was
adopted in June 2002, APHIS–VS has cooperated with the
International Association of Fish and Wildlife Agencies to
promote uniform, nationwide surveillance while allowing
flexibility to meet individual State situations and needs.
Since beginning to receive line-item funding for CWD
in FY 2003, APHIS-VS has been providing assistance to
State wildlife agencies and tribes through cooperative
agreements to address the disease in free-ranging deer
and elk. This funding has covered surveillance testing
for some 90,000 hunter-killed and targeted animals in
the 2002–03 and the 2003–04 hunting seasons. Similar
numbers were projected for 2004–05 and 2005–06. All
50 States participated in the first 2 years of the program,
and 47 States requested and received funding in FY 2005.
Funding is distributed through a tiered system based on risk
of disease developed in consultation with the International
Association of Fish and Wildlife Agencies. In addition to
individual tribal assistance, an agreement with the Native
American Fish and Wildlife Society funds five regional CWD
tribal biologists to assist tribes with CWD activities.
Disease Status—In FY 2005, 15,628 farmed cervids were
tested for CWD as compared to more than 15,000 animals
in FY 2004 and more than 12,000 in FY 2003. From 1997
through 2005, CWD had been found in 32 farmed elk
herds and 8 farmed deer herds in 9 States (table 11).
Of the 40 positive herds identified as of December 31,
2005, 6 (4 in Colorado and 2 in Wisconsin) remained
under State quarantine and 33 had been depopulated.
The quarantine was lifted from one herd that underwent
rigorous surveillance for more than 5 years with no further
evidence of disease.
Challenges—The key challenges in managing CWD result
from the fact that cervids fall under multiple jurisdictions.
In 2002, at the request of Congress, an interagency group
was convened to develop a management plan to assist
States, Federal agencies, and Native American tribes in
managing CWD in captive and wild herds. Currently, this
plan is implemented by State and Federal agencies, as
budgets permit. A progress report on the implementation
of the plan was completed and presented to Congress in
May 2004.
Additional challenges are related to the difficulties
associated with testing wild cervids. High sample
throughput and more rapid test technology were needed
to meet the needs of wildlife agencies. By expanding
its contract group of State and university laboratories,
NVSL now has 26 laboratories approved to conduct CWD
testing. In addition, the Center for Veterinary Biologics has
approved four CWD antigen test kits based on enzymelinked
immunosorbent assay (ELISA), allowing faster
testing and greater throughput for surveillance testing of
wild cervids.
50 2005 United States Animal Health Report
snip...full text 120 pages ;
http://www.aphis.usda.gov/publications/animal_health/content/printable_version/2005_us_animal_health_report.pdf
PLEASE NOTE;
In cattle, BSE is one of the FAD differential diagnoses
of concern for the complaint of central nervous system
(CNS) signs, such as changes in temperament, abnormal
posture, and ataxia. In 2005, VS continued surveillance
for BSE through its Enhanced BSE Surveillance Plan
established in 2004, testing 419,268 brain submissions
and conducting
12 FAD investigations for the complaint of
CNS signs in bovines. ....
snip...FROM HOW MANY DOWNERS ???
Cattle Death Loss by Cause, 2005
Since 1990, the percentage of cattle inventory lost to all
causes has remained relatively constant at approximately
2 percent. The percentage of calf crop lost decreased
from 7.25 percent in 1990 to just over 6 percent in 2005
(fig. 27).
Cause of Loss—Predator and nonpredator cause-of-loss
estimates for cattle and calves started in 1991 and were
repeated for 1995, 2000, and 2005 as a cooperative effort
between NASS and APHIS. The most recent estimates
(2005) are presented here (fig. 28). Overall, 98.0 percent
of cattle losses and 93.3 percent of calf losses were due
to nonpredator causes. Important causes of loss for cattle
were calving problems (11.1 percent), digestive problems
(11.1 percent), and respiratory problems (24.8 percent).
The most frequently reported causes of loss for calves
were respiratory problems (31.8 percent), digestive
problems (21.2 percent), and calving problems
(17.7 percent) (fig. 29).
SNIP...CATTLE UNKNOWN CAUSE OF DEATH AT 13.3 % AND CALVES AT 11.5 %
NOW, for the rest of the story FROM ABOVE THAT ONLY ;
___12__ FAD investigations for the complaint of
CNS signs in bovines. .... WHAT A HOOT !!!
MORE FACTS BELOW AND REAL FIGURES ;
Non-Ambulatory Cattle and Calves
Released May 5, 2005, by the National Agricultural Statistics Service (NASS), Agricultural Statistics Board, U.S. Department
of Agriculture. For information on Non-ambulatory Cattle and Calves call Mike Miller at 720-3040, office hours 7:30 a.m. to
4:30 p.m. ET.
Non-Ambulatory Cattle and Calves
Non-ambulatory cattle and calves in the United States totaled 465,000 head during 2003 and
450,000 head during 2004. The number of non-ambulatory cattle 500 pounds or greater totaled
280,000 head in 2003 and 270,000 head in 2004. The number of calves under 500 pounds reported
as non-ambulatory totaled 185,000 head in 2003 and 180,000 head in 2004.
The number of operations that reported non-ambulatory cattle and calves was 103,000 in 2003 and
81,000 in 2004. In 2003, there were 66,800 beef cow operations reporting non-ambulatory cattle
and calves compared to 49,700 in 2004. There were 22,800 dairy operations reporting nonambulatory
cattle and calves in 2003 compared to 23,000 in 2004.
This report is released as a cooperative effort between the National Agricultural Statistics Service
and Animal and Plant Health Inspection Service - Veterinary Services. Data for this report were
collected on the January 1, 2004 and 2005 Cattle Surveys.
SNIP...FULL TEXT ;
http://usda.mannlib.cornell.edu/usda/current/nacac/nacac-05-05-2005.pdf
Audit Report
Animal and Plant Health Inspection Service
Bovine Spongiform Encephalopathy (BSE) Surveillance Program – Phase II
and
Food Safety and Inspection Service
Controls Over BSE Sampling, Specified Risk Materials, and Advanced Meat Recovery Products - Phase III
Report No. 50601-10-KC January 2006
Finding 2 Inherent Challenges in Identifying and Testing High-Risk Cattle Still Remain
Our prior report identified a number of inherent problems in identifying and testing high-risk cattle. We reported that the challenges in identifying the universe of high-risk cattle, as well as the need to design procedures to obtain an appropriate representation of samples, was critical to the success of the BSE surveillance program. The surveillance program was designed to target nonambulatory cattle, cattle showing signs of CNS disease (including cattle testing negative for rabies), cattle showing signs not inconsistent with BSE, and dead cattle. Although APHIS designed procedures to ensure FSIS condemned cattle were sampled and made a concerted effort for outreach to obtain targeted samples, industry practices not considered in the design of the surveillance program reduced assurance that targeted animals were tested for BSE.
In our prior report, we recommended that APHIS work with public health and State diagnostic laboratories to develop and test rabies-negative samples for BSE. This target group is important for determining the prevalence of BSE in the United States because rabies cases exhibit clinical signs not inconsistent with BSE; a negative rabies test means the cause of the clinical signs has not been diagnosed.
APHIS agreed with our recommendation and initiated an outreach program with the American Association of Veterinary Laboratory Diagnosticians, as well as State laboratories. APHIS also agreed to do ongoing monitoring to ensure samples were obtained from this target population.
Although APHIS increased the samples tested from this target group as compared to prior years, we found that conflicting APHIS instructions on the ages of cattle to test resulted in inconsistencies in what samples were submitted for BSE testing. Therefore, some laboratories did not refer their rabies negative samples to APHIS in order to maximize the number tested for this critical target population. In addition, APHIS did not monitor the number of submissions of rabies negative samples for BSE testing from specific laboratories.
According to the Procedure Manual for BSE Surveillance, dated October 2004, the target population includes:
Central nervous system (CNS) signs and/or rabies negative - sample animals of any age (emphasis added):
a. Diagnostic laboratories –samples submitted due to evidence of CNS clinical signs.
Rabies Negative Samples
USDA/OIG-A/50601-10-KC Page 19 USDA/OIG-A/50601-10-KC Page 20
b. Public health laboratories – rabies negative cases.
c. Slaughter facilities – CNS ante mortem condemned at slaughter, sampled by FSIS.
d. On-the-farm – CNS cattle that do not meet the criteria for a foreign animal disease investigation.
For FYs 2002, 2003, and 2004 (through February 2004), NVSL received 170, 133, and 45 rabies-negative samples, respectively. Between June 1, 2004, and May 29, 2005, the number of samples received for testing increased to 226 rabies suspect samples. The collection sites submitting these samples follow.
Number of Rabies
Suspect Submissions *
Slaughter Plant
0
Renderer
2
On-Farm
11
Public Health Lab
94
Diagnostic Lab
81
3D-4D
8
Other
4
Collection Site
Total
200
* 26 were tested but not counted by APHIS towards meeting the target goals because the obex was not submitted.
We obtained a copy of a memorandum, dated July 13, 2004, that APHIS sent to diagnostic and public health laboratories providing them instructions on submitting samples for cattle showing signs of CNS diseases, but testing negative for rabies. The letter was sent to about 170 State veterinary diagnostic and public health laboratories and discussed the need to submit specimens to NVSL of all adult cattle (emphasis added) that showed signs of CNS diseases, but tested negative for rabies. This directive did not specify the age of the cattle. The Procedure Manual for BSE Surveillance, dated October 2004, specified samples of cattle of any age should be submitted.
We contacted laboratories in six States to determine if it was standard procedure to submit all negative rabies samples to NVSL. We found that, because of the lack of specificity in the APHIS letter and inadequate followup by APHIS, there were inconsistencies in the age of cattle samples submitted for BSE testing. For those States contacted, the following samples were submitted versus tested as negative for rabies.
USDA/OIG-A/50601-10-KC Page 21
Rabies Negative Tests Not Sent for BSE Testing Since June 1, 2004
State
Negative Rabies Tests
Not Sent for BSE Testing
Pennsylvania a/
15
18
Kansas b/
69
16
Wisconsin c/
1
11
South Dakota d/
0
7
Arizona e/
5
0
Mississippi e/
4
0
Total
Sent for BSE Testing
33
85
12
7
5
4
146
94
52
a/ A Pennsylvania laboratory official said only rabies negative cattle over 20 months of age were submitted for BSE testing. The laboratory did not submit 18 samples for BSE testing because the animals were less than 20 months of age.
b/ Kansas laboratory officials said early in the expanded surveillance program, there was confusion as to the cattle ages that should be submitted for BSE testing. They did not know if cattle should be submitted that were above 20 months or 30 months of age. Of the 16 animals not submitted for BSE testing, 14 were under 20 months of age from early in the expanded surveillance program. The other two animals were not tested due to internal laboratory issues. The Kansas and Nebraska area office officials contacted the laboratory and told the officials to submit rabies negative cattle of any age for BSE testing. The laboratory now submits all rabies negative cattle for BSE testing.
c/ A Wisconsin laboratory official said only rabies negative cattle samples 30 months of age or older are submitted for BSE testing. Of the 11 animals not submitted for BSE testing, 8 were less than 30 months of age. Wisconsin laboratory officials were not certain why the other three samples were not submitted.
d/ Laboratory officials from South Dakota said they did not receive notification from APHIS regarding the submission of rabies negative cases for BSE testing. The section supervisor and laboratory director were not aware of any letter sent to the laboratory. The section supervisor said most bovine rabies tests at the laboratory are performed on calves. We confirmed the laboratory’s address matched the address on APHIS’ letter distribution list. However, there was no evidence that the South Dakota area office contacted the laboratory. The laboratory was not listed on the documentation from the APHIS regional office detailing the area office contacts with laboratory personnel. We contacted the South Dakota area office and were advised that while some contact had been made with the laboratory, the contact may have involved Brucellosis rather than BSE. On May 4, 2005, the area office
33 Report from the Secretary’s Advisory Committee on Foreign Animal and Poultry Diseases, February 13, 2004.
advised us they recently contacted the laboratory regarding the submission of rabies negative samples for BSE testing.
e/ Arizona and Mississippi laboratory officials said they submitted all rabies negative samples for BSE testing regardless of the age of the animal.
An NVSL official stated that APHIS is not concerned with rabies negatives samples from cattle less than 30 months of age. This position, however, is contrary to APHIS’ published target population.
Our prior audit recognized the significant challenge for APHIS to obtain samples from some high-risk populations because of the inherent problems with obtaining voluntary compliance and transporting the carcasses for testing. USDA issued rules to prohibit nonambulatory animals (downers) from entering the food supply at inspected slaughterhouses. OIG recommended, and the International Review Subcommittee33 emphasized, that USDA should take additional steps to assure that facilitated pathways exist for dead and nonambulatory cattle to allow for the collection of samples and proper disposal of carcasses. Between June 1, 2004, and May 31, 2005, the APHIS database documents 27,617 samples were collected showing a reason for submission of nonambulatory and 325,225 samples were collected with reason of submission showing "dead."
APHIS made extensive outreach efforts to notify producers and private veterinarians of the need to submit and have tested animals from these target groups. They also entered into financial arrangements with 123 renderers and other collection sites to reimburse them for costs associated with storing, transporting, and collecting samples. However, as shown in exhibit F, APHIS was not always successful in establishing agreements with non-slaughter collection sites in some States. APHIS stated that agreements do not necessarily reflect the entire universe of collection sites and that the presentation in exhibit F was incomplete because there were many collection sites without a payment involved or without a formal agreement. We note that over 90 percent of the samples collected were obtained from the 123 collection sites with agreements and; therefore, we believe agreements offer the best source to increase targeted samples in underrepresented areas.
We found that APHIS did not consider industry practices in the design of its surveillance effort to provide reasonable assurance that cattle exhibiting possible clinical signs consistent with BSE were tested. Slaughter facilities do not always accept all cattle arriving for slaughter because of their business requirements. We found that, in one State visited, slaughter facilities pre-screened and rejected cattle (sick/down/dead/others not meeting business
Downers and Cattle that Died on the Farm
USDA/OIG-A/50601-10-KC Page 22 USDA/OIG-A/50601-10-KC Page 23
34 FSIS regulations do not specifically address the designation of an establishment’s "official" boundaries; however, FSIS Notices 29-04 (dated May 27, 2004) and 40-04 (dated July 29, 2004) make it clear that FSIS inspection staff are not responsible for sampling dead cattle that are not part of the "official" premises.
35 APHIS’ area office personnel stated that it was their understanding that some establishments in the State were not presenting cattle that died or were down on the transport vehicle to FSIS for ante mortem inspection. The dead and down cattle were left in the vehicle, if possible. In rare circumstances, dead cattle may be removed from the trailer by plant personnel to facilitate the unloading of other animals.
36 A May 20, 2004, Memorandum between the Administrators of APHIS and FSIS.
standards) before presentation for slaughter in areas immediately adjacent or contiguous to the official slaughter establishment. These animals were not inspected and/or observed by either FSIS or APHIS officials located at the slaughter facilities.
FSIS procedures state that they have no authority to inspect cattle not presented for slaughter. Further, APHIS officials stated they did not believe that they had the authority to go into these sorting and/or screening areas and require that the rejected animals be provided to APHIS for BSE sampling. Neither APHIS nor FSIS had any process to assure that animals left on transport vehicles and/or rejected for slaughter arrived at a collection site for BSE testing. FSIS allows slaughter facilities to designate the area of their establishment where federal inspection is performed; this is designated as the official slaughter establishment.34
We observed animals that were down or dead in pens outside the official premises that were to be picked up by renderers. Animals that were rejected by plant personnel were transported off the premises on the same vehicles that brought them to the plant.35
A policy statement36 regarding BSE sampling of condemned cattle at slaughter plants provided that effective June 1, 2004, FSIS would collect BSE samples for testing: 1) from all cattle regardless of age condemned by FSIS upon ante mortem inspection for CNS impairment, and 2) from all cattle, with the exception of veal calves, condemned by FSIS upon ante mortem inspection for any other reason.
FSIS Notice 28-04, dated May 20, 2004, informed FSIS personnel that, "FSIS will be collecting brain samples from cattle at federally-inspected establishments for the purpose of BSE testing." The notice further states that, "Cattle off-loaded from the transport vehicle onto the premises of the federally-inspected establishment (emphasis added), whether dead or alive, will be sampled by the FSIS Public Health Veterinarian (PHV) for BSE after the cattle have been condemned during ante mortem inspection. In addition, cattle passing ante mortem inspection but later found dead prior to slaughter will be condemned and be sampled by the FSIS PHV."
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37 FSIS Notice 40-04, dated July 29, 2004.
38 FSIS Notice 29-04, dated May 27, 2004.
APHIS has the responsibility for sampling dead cattle off-loaded onto plant-owned property that is adjoining to, but not considered part of, the "official premises.37 FSIS procedures38 provide that "Dead cattle that are off-loaded to facilitate the off-loading of live animals, but that will be re-loaded onto the transport vehicle, are not subject to sampling by FSIS.
While performing our review in one State, we reviewed the circumstances at two slaughter facilities in the State that inspected and rejected unsuitable cattle before the animals entered the official receiving areas of the plants. This pre-screening activity was conducted in areas not designated by the facility as official premises of the establishment and not under the review or supervision of FSIS inspectors. The plant rejected all nonambulatory and dead/dying/sick animals delivered to the establishment. Plant personnel refused to offload any dead or downer animals to facilitate the offloading of ambulatory animals. Plant personnel said that the driver was responsible for ensuring nonambulatory animals were humanely euthanized and disposing of the carcasses of the dead animals. Plant personnel informed us that they did not want to jeopardize contracts with business partners by allowing unsuitable animals on their slaughter premises.
In the second case, one family member owned a slaughter facility while another operated a livestock sale barn adjacent to the slaughter facility. The slaughter facility was under FSIS’ supervision while the sale barn was not. Cattle sometimes arrived at the sale barn that were sick/down/dead or would die or go down while at the sale barn. According to personnel at the sale barn, these animals were left for the renderer to collect. The healthy ambulatory animals that remained were marketed to many buyers including the adjacent slaughter facility. When the slaughter facility was ready to accept the ambulatory animals for processing, the cattle would be moved from the sale barn to the slaughter facility where they were subject to FSIS’ inspection.
We requested the slaughter facilities to estimate the number of cattle rejected on a daily basis (there were no records to confirm the estimates). We visited a renderer in the area and found that the renderer had a contract with APHIS to collect samples for BSE testing. In this case, although we could not obtain assurance that all rejected cattle were sampled, the renderer processed a significant number of animals, as compared to the slaughter plants’ estimates of those rejected. Due to the close proximity (less than 5 miles) of the renderer to the slaughter facilities, and the premium it paid for dead cattle that were in good condition, there was a financial incentive for transport drivers to dispose of their dead animals at this renderer.
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In our discussions with APHIS officials in Wisconsin and Iowa, they confirmed that there were plants in their States that also used pre-screening practices. On May 27, 2005, we requested APHIS and FSIS to provide a list of all slaughter facilities that pre-screened cattle for slaughter in locations away from the area designated as the official slaughter facility. Along with this request, we asked for information to demonstrate that either APHIS or FSIS confirmed there was a high likelihood that high-risk animals were sampled at other collection sites.
In response to our request, the APHIS BSE Program Manager stated that APHIS did not have information on slaughter plants that pre-screen or screen their animals for slaughter suitability off their official plant premises. To their knowledge, every company or producer that submits animals for slaughter pre-sorts or screens them for suitability at various locations away from the slaughter facility. For this reason, USDA focused its BSE sample collection efforts at other types of facilities such as renderers, pet food companies, landfills, and dead stock haulers. Further, in a letter to OIG on June 14, 2005, the administrators of APHIS and FSIS noted the following:
"…we believe that no specific actions are necessary or appropriate to obtain reasonable assurance that animals not presented for slaughter are being tested for BSE. There are several reasons for our position. First, we do not believe that the practice is in fact causing us to not test a significant enough number of animals in our enhanced surveillance program to invalidate the overall results. Second, OIG has concluded that because of the geographical proximity and business relationships of the various entities involved in the case investigated, there is reasonable assurance that a majority of the rejected cattle had been sampled. Third, it is also important to remember that the goal of the enhanced surveillance program is to test a sufficient number of animals to allow us to draw conclusions about the level of BSE (if any) in the American herd…We believe that the number we may be not testing because of the "pre-sorting" practice does not rise to a significant level. The number of animals tested to date has far exceeded expectations, so it is reasonable to infer that there are few of the animals in question, or that we are testing them at some other point in the process…APHIS estimated…there were approximately 446,000 high risk cattle…[and APHIS has]…tested over 375,000 animals in less than 1 year. This indicated that we are missing few animals in the high-risk population, including those that might be pre-sorted before entering a slaughter facility’s property."
We obtained 123 APHIS sampling agreements and contracts with firms and plotted their locations within the United States (see exhibit F). We also analyzed the samples tested to the BSE sampling goals allocated to each State under the prior surveillance program. This analysis showed that there are
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39APHIS noted that sites with agreements do not necessarily reflect the entire universe of collection sites and at some sites APHIS collects samples with no payment involved and no agreement in place. OIG agrees that not all collection sites are reflected in our presentation of the 123 sites with reimbursable agreements. OIG believes obtaining sampling agreements is one of the primary methods available to increase sample numbers in areas with sampling gaps.
sampling gaps in two large areas of the United States where APHIS did not have contracts with collection sites. These two areas are shown in the following chart (Montana, South Dakota, North Dakota and Wyoming – Group 1 and Louisiana, Oklahoma, Arkansas, and Tennessee – Group 2):
State
Original Sampling Goal Based on (268,500 sampling goal)
Samples collected as of May 31, 2005
No. of BSE Sampling Agreements/
Contracts39
MT
5,076
4,894
2
SD
6,938
4,146
1
ND
3,616
3,442
0
WY
2,513
2,452
0
AREA TOTAL
14,934
OK
7,792
5,385
1
AR
3,672
3,319
0
TN
4,938
1,888
1
LA
2,312
1,860
1
AREA TOTAL
Deficit
182
2,792
174
61
2,407
353
3,050
452
12,452
APHIS notes that for the current surveillance program, it had established regional goals and APHIS was not trying to meet particular sampling levels in particular States. However, we believe that it would be advantageous for APHIS to monitor collection data and increase outreach when large geographical areas such as the above States do not provide samples in proportion to the numbers and types of cattle in the population.
We also disagree with APHIS/FSIS’ contention that because they have tested over 375,000 of their 446,000 estimate of high risk cattle, few in the high-risk population are being missed, including those that might be pre-screened before entering a slaughter facility’s property. In our prior audit, we reported that APHIS underestimated the high-risk population; we found that this estimate should have been closer to 1 million animals (see Finding 1). We recognize that BSE samples are provided on a voluntary basis; however, APHIS should consider industry practice in any further maintenance surveillance effort. Animals unsuitable for slaughter exhibiting symptoms not inconsistent with BSE should be sampled and their clinical signs recorded. However, this cited industry practice results in rejected animals not being made available to either APHIS or FSIS veterinarians for their observation and identification of clinical signs exhibited ante mortem. Although these animals may be sampled later at other collection sites, the animals are provided post mortem without information as to relevant clinical signs exhibited ante mortem. For these reasons, we believe APHIS needs to
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observe these animals ante mortem when possible to assure the animals from the target population are ultimately sampled and the clinical signs evaluated.
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http://www.usda.gov/oig/webdocs/50601-10-KC.pdf
USDA Testing Protocols and Quality Assurance Procedures
In November 2004, USDA announced that its rapid screening test produced an inconclusive BSE test result. A contract laboratory ran its rapid screening test on a brain sample collected for testing and produced three high positive reactive results. As required, the contract laboratory forwarded the inconclusive sample to APHIS’ National Veterinary Services Laboratories (NVSL) for confirmation. NVSL repeated the rapid screening test, which again produced three high positive reactive results. Following established protocol, NVSL ran its confirmatory test, an immunohistochemistry (IHC) test, which was interpreted as negative for BSE.
Faced with conflicting results between the rapid screening and IHC tests, NVSL scientists recommended additional testing to resolve the discrepancy but APHIS headquarters officials concluded that no further testing was necessary since testing protocols were followed and the confirmatory test was negative. In our discussions with APHIS officials, they justified their decision to not do additional testing because the IHC test is internationally recognized as the "gold standard" of testing. Also, they believed that
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conducting additional tests would undermine confidence in USDA’s testing protocols.
OIG obtained evidence that indicated additional testing was prudent. We came to this conclusion because the rapid screening tests produced six high positive reactive results, the IHC tests conflicted, and various standard operating procedures were not followed. Also, our review of the relevant scientific literature, other countries’ protocols, and discussions with experts led us to conclude that additional confirmatory testing should be considered in the event of conflicting test results.
To maintain objectivity and independence, we requested that USDA’s Agricultural Research Service (ARS) perform the Office International des Epizooties (OIE) Scrapie-Associated Fibrils (SAF) immunoblot test. The additional testing produced positive results. To confirm, the Secretary of Agriculture requested that an internationally recognized BSE laboratory in Weybridge, England (Weybridge) perform additional testing. Weybridge conducted various tests, including their own IHC tests and three Western blot tests. The tests confirmed that the cow was infected with BSE. The Secretary immediately directed USDA scientists to work with international experts to develop new protocols that include performing dual confirmatory tests in the event of an inconclusive BSE screening test.
We attribute the failure to identify the BSE positive sample to rigid protocols, as well as the lack of adequate quality assurance controls over its testing program. Details of our concerns are discussed in Findings 3 and 4.
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Section 2. Testing Protocols and Quality Assurance Controls In November 2004, USDA announced that its rapid screening test, Bio-Rad Enzyme Linked Immunosorbent Assay (ELISA), produced an inconclusive BSE test result as part of its enhanced BSE surveillance program. The ELISA rapid screening test performed at a BSE contract laboratory produced three high positive reactive results.40 As required,41 the contract laboratory forwarded the inconclusive sample to the APHIS National Veterinary Services Laboratories (NVSL) for confirmatory testing. NVSL repeated the ELISA testing and again produced three high positive reactive results.42 In accordance with its established protocol, NVSL ran its confirmatory test, an immunohistochemistry (IHC) test, which was interpreted as negative for BSE. In addition, NVSL performed a histological43 examination of the tissue and did not detect lesions44 consistent with BSE. Faced with conflicting results, NVSL scientists recommended additional testing to resolve the discrepancy but APHIS headquarters officials concluded no further testing was necessary because testing protocols were followed. In our discussions with APHIS officials, they justified their decision not to do additional testing because the IHC is internationally recognized as the “gold standard.” Also, they believed that conducting additional tests would undermine confidence in USDA’s established testing protocols. However, OIG obtained evidence that indicated additional testing was prudent to ensure that USDA’s testing protocols were effective in detecting BSE and that confidence in USDA’s testing procedures was maintained. OIG came to this conclusion because the rapid tests produced six high positive reactive results, confirmatory testing conflicted with the rapid test results, and various standard operating procedures were not followed. Also, our review of scientific literature, other country protocols, as well as discussions with internationally recognized experts led us to conclude that confirmatory testing should not be limited when conflicting test results are obtained. To maintain objectivity and independence in our assessment, we requested the USDA Agricultural Research Service (ARS) perform the Office International des Epizooties (OIE) Scrapie-Associated Fibrils (SAF) 40 ELISA test procedures require two additional (duplicate) tests if the initial test is reactive, before final interpretation. If either of the duplicate tests is reactive, the test is deemed inconclusive. 41 Protocol for BSE Contract Laboratories to Receive and Test Bovine Brain Samples and Report Results for BSE Surveillance Standard Operating Procedure (SOP), dated October 26, 2004. 42 The NVSL conducted an ELISA test on the original material tested at the contract laboratory and on two new cuts from the sample tissue. 43 A visual examination of brain tissue by a microscope. 44 A localized pathological change in a bodily organ or tissue.
immunoblot.45 ARS performed the test at the National Animal Disease Center because NVSL did not have the necessary equipment46 (ultracentrifuge) to do the test. APHIS scientists observed and participated, as appropriate, in this effort. The additional tests conducted by ARS produced positive results. To confirm this finding, the Secretary requested the internationally recognized BSE reference laboratory in Weybridge, England, (Weybridge) to perform additional confirmatory testing. Weybridge conducted various tests, including their own IHC methods, as well as three Western blot methods. The tests confirmed that the suspect cow was infected with BSE. Also, Weybridge confirmed this case as an unequivocal positive case of BSE on the basis of IHC. As a result of this finding, the Secretary immediately directed USDA scientists to work with international experts to develop a new protocol that includes performing dual confirmatory tests in the event of another inconclusive BSE screening test. Finding 3 Rigid Protocols Reduced the Likelihood BSE Could be Detected APHIS relied on a single test method, as well as a histological examination of tissue for lesions consistent with BSE, to confirm the presence of BSE even though discrepant test results indicated further testing may be prudent. When IHC test results were interpreted as negative, APHIS concluded the sample tested negative for BSE. Subsequent independent tests initiated by OIG using a different testing method, as well as confirmatory testing by Weybridge, determined that the suspect sample was a positive case of BSE. APHIS Declares BSE Sample Negative Despite Conflicting Results When the tissue sample originally arrived at NVSL in November 2004 from the contract lab, NVSL scientists repeated the ELISA screening test and again produced three high positive reactive results. NVSL scientists cut out two sections of the brain sample for IHC testing. One section was used for an experimental procedure that was not part of the confirmatory testing protocol, and the other cut was for normal IHC testing using scrapie for a positive control.47 According to NVSL scientists, the experimental test results were inconclusive but the IHC test was interpreted as negative. The NVSL scientists were concerned with the inconsistencies and conducted 45 The OIE SAF immunoblot is an internationally recognized confirmatory test, often referred to as a Western blot test. There are different types of Western blots; the OIE SAF immunoblot includes enrichment steps taken with the sample prior to the standard Western blot steps. 46 APHIS has now ordered the necessary equipment for NVSL. USDA/OIG-A/50601-10-KC Page 32
47 A positive control is a sample that is known to contain a given disease or react in the test. The sample then can be used to make sure that the test for that disease works properly. In the case of BSE, tissue infected with either scrapie or BSE can serve as a positive control for an IHC test for BSE since both are different forms of the same disease (transmissible spongiform encephalopathy or TSE).
another IHC test using BSE as a positive control.48 The test result was also interpreted as negative. Also, according to the NVSL scientists, the histological examination of the tissue did not detect lesions consistent with BSE. After the second negative IHC test, NVSL scientists supported doing additional testing. They prepared a plan for additional tests; if those tests had been conducted, BSE may have been detected in the sample. The additional tests recommended by NVSL scientists, but not approved by APHIS Headquarters officials, were the IHC using other antibodies (IHC testing using different antibodies ultimately produced positive results); IHC testing of additional regions of the brain (the cerebellum tested positive); regular and enriched (OIE-like) Western blots (the obex and cerebellum tested positive); and variable rapid tests (the obex and cerebellum tested positive with two different rapid tests). NVSL officials also recommended that the sample be sent to Weybridge for confirmatory testing (to conduct IHC and OIE Western blot tests). In June 2005, Weybridge conducted IHC testing with three different antibodies, including the antibody used in the United States (tested positive), the OIE Western blot (tested positive), a modified commercial kit Western blot (negative) and the NaPTA49 Western blot (tested positive). We obtained information as to the differing protocols used by other countries. We found that while APHIS determined that additional testing was unnecessary after the IHC test, other countries have used multiple tests to confirm positives. In Japan, for example, all reactive screening test samples are examined by both IHC and a Western blot (different from the OIE SAF immunoblot). In the United Kingdom (U.K.), IHC and Western blot (different from the OIE SAF immunoblot) tests are used for all animals that test positive with a screening test. When IHC and the Western blot fail to confirm a positive rapid test, the U.K. resorts to a third test, the OIE SAF immunoblot. With these procedures in place, both Japan and the U.K. have found BSE cases that were rapid test reactive, IHC negative, and finally confirmed positive with a Western blot. Evidence Indicated Additional Testing Would Be Prudent We also spoke with an internationally recognized BSE expert regarding the advisability of limiting confirmatory testing when conflicting results are obtained. This official expressed concern about limiting confirmatory tests to the IHC despite its status as one of the “gold standard” tests. He advised that the IHC is not one test; it is a test method that can vary significantly in sensitivity from laboratory to laboratory. New antibodies can improve or
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48 The NVSL uses scrapie as the positive control as part of its normal IHC testing procedures. Due to the conflicting results between the ELISA and IHC tests, the NVSL conducted another IHC test with BSE as the positive control. Subsequently, the NVSL modified the Confirming Inconclusive Results from BSE Testing Laboratories at the NVSL SOP to show that all IHC tested BSE inconclusive samples from contract laboratories will use BSE as the positive control. 49 Sodium phosphotungstic acid.
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reduce sensitivity, as can variations in many of the reagents50 used. He explained that his laboratory had experienced cases where an initial confirmatory IHC test was challenged by either a more extensive IHC test or “…applying a more sensitive immunoblot.” He emphasized the importance of having additional confirmatory testing to resolve discrepant results since there are many variables, and most of the variability appears to be due to test performance of the laboratory. OIG became concerned that APHIS relied on its confirmatory test methods when rapid sc