Subject: Factors determining the potential for vCJD via surgical instruments
Date: August 2, 2006 at 6:39 am PST
Factors determining the potential for
onward transmission of variant
Creutzfeldt–Jakob disease via
surgical instruments
Tini Garske1,*, Hester J. T. Ward2, Paul Clarke1, Robert G. Will2
and Azra C. Ghani1
1Department of Epidemiology and Population Health,
London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
2National Creutzfeldt–Jakob Disease Surveillance Unit, Western General Hospital,
Edinburgh EH4 2XU, UK
While the number of variant Creutzfeldt–Jakob disease (vCJD) cases continues to decline,
concern has been raised that transmission could occur directly from one person to another
through routes including the transfer of blood and shared use of surgical instruments. Here
we firstly present data on the surgical procedures undertaken on vCJD patients prior to onset
of clinical symptoms, which supports the hypothesis that cases via this route are possible. We
then apply a mathematical framework to assess the potential for self-sustaining epidemics via
surgical procedures. Data from hospital episode statistics on the rates of high- and mediumrisk
procedures in the UK were used to estimate model parameters, and sensitivity to other
unknown parameters about surgically transmitted vCJD was assessed. Our results
demonstrate that a key uncertainty determining the scale of an epidemic and whether it is
self-sustaining is the number of times a single instrument is re-used, alongside the infectivity
of contaminated instruments and the effectiveness of cleaning. A survey into the frequency of
re-use of surgical instruments would help reduce these uncertainties.
Keywords: variant Creutzfeldt–Jakob disease; self-sustaining epidemic;
mathematical model; epidemiology
1. INTRODUCTION
To date it is believed that the majority of clinical cases
of variant Creutzfeldt–Jakob disease (vCJD) in the UK
have been caused by consumption of Bovine spongiform
encephalopathy (BSE)-infected beef (Bruce et al. 1997;
Hill et al. 1997; Scott et al. 1999). Despite high
estimates of the number of BSE-infected cattle that
entered the food supply (in the order of 3–4 million
animals (Donnelly et al. 2002)), the number of cases of
vCJD has remained low with 161 cases to the end of
2005, and the annual incidence steadily decreasing since
2000. Estimates for the total scale of the epidemic
through this route have reduced over time and now lie
in the low hundreds (Clarke & Ghani 2005).
A survey of appendix and tonsil tissues (Hilton et al.
2004) estimated a much higher prevalence of infection in
the population than suggested by the clinical cases. This
finding is best explained by the hypothesis that a large
proportion (84.4%) of infections are sub-clinical (i.e. will
never go on to develop symptoms within their lifetime;
Clarke & Ghani 2005). Evidence for a sub-clinical vCJD
state has been found in animal studies (Hill et al. 2000;
Hill & Collinge 2003; Bishop et al. 2006). Infection is
detectable throughout the CNS and lymphatic system in
patients with clinical vCJD (Wadsworth et al. 2001). In
addition, the abnormal formof the prion protein (PrPSc)
has been detected in the spleen of a patient who died
from other causes (Peden et al. 2004) and in the
appendix of a vCJD case removed 3 years prior to
their death (Hilton et al. 1998). Given that infectious
PrPSc is detectable in patients showing no clinical
symptoms, it is possible that it could be transmitted
through surgical procedures. Surgical instruments are
decontaminated routinely before use on another patient.
However, research suggests that PrP binds strongly to
stainless steel and that current sterilisation procedures
are unlikely to be effective because of the high
temperatures required to deactivate PrPSc (Flechsig
et al. 2001; Yan et al. 2004). Furthermore, a survey of
decontamination practices has shown that past practices
fell short of the expected standard in many hospitals
(Estates 2000). Although steps have been taken to
improve the situation (Estates 2001), it is likely that the
reality of decontamination is still less than perfect and
hence that residual infectivity will remain.
J. R. Soc. Interface
doi:10.1098/rsif.2006.0142
Published online
*Author for correspondence ([email protected]).
Received 22 May 2006
Accepted 21 June 2006 1 q 2006 The Royal Society
snip....
full text ;
http://www.journals.royalsoc.ac.uk/media/7hxdahxwvm0wxxrrvbfk/contributions/8/0/v/8/80v81437446nu2m5.pdf
NOT TO FORGET THE SPORADIC CJDs ;
Transmission of Creutzfeldt-Jakob disease to a chimpanzee by electrodes contaminated during neurosurgery.
Gibbs CJ Jr, Asher DM, Kobrine A, Amyx HL, Sulima MP, Gajdusek DC.
Laboratory of Central Nervous System Studies, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Stereotactic multicontact electrodes used to probe the cerebral cortex of a middle aged woman with progressive dementia were previously implicated in the accidental transmission of Creutzfeldt-Jakob disease (CJD) to two younger patients. The diagnoses of CJD have been confirmed for all three cases. More than two years after their last use in humans, after three cleanings and repeated sterilisation in ethanol and formaldehyde vapour, the electrodes were implanted in the cortex of a chimpanzee. Eighteen months later the animal became ill with CJD. This finding serves to re-emphasise the potential danger posed by reuse of instruments contaminated with the agents of spongiform encephalopathies, even after scrupulous attempts to clean them.
PMID: 8006664 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8006664&dopt=Abstract
TSS
Date: August 2, 2006 at 6:39 am PST
Factors determining the potential for
onward transmission of variant
Creutzfeldt–Jakob disease via
surgical instruments
Tini Garske1,*, Hester J. T. Ward2, Paul Clarke1, Robert G. Will2
and Azra C. Ghani1
1Department of Epidemiology and Population Health,
London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
2National Creutzfeldt–Jakob Disease Surveillance Unit, Western General Hospital,
Edinburgh EH4 2XU, UK
While the number of variant Creutzfeldt–Jakob disease (vCJD) cases continues to decline,
concern has been raised that transmission could occur directly from one person to another
through routes including the transfer of blood and shared use of surgical instruments. Here
we firstly present data on the surgical procedures undertaken on vCJD patients prior to onset
of clinical symptoms, which supports the hypothesis that cases via this route are possible. We
then apply a mathematical framework to assess the potential for self-sustaining epidemics via
surgical procedures. Data from hospital episode statistics on the rates of high- and mediumrisk
procedures in the UK were used to estimate model parameters, and sensitivity to other
unknown parameters about surgically transmitted vCJD was assessed. Our results
demonstrate that a key uncertainty determining the scale of an epidemic and whether it is
self-sustaining is the number of times a single instrument is re-used, alongside the infectivity
of contaminated instruments and the effectiveness of cleaning. A survey into the frequency of
re-use of surgical instruments would help reduce these uncertainties.
Keywords: variant Creutzfeldt–Jakob disease; self-sustaining epidemic;
mathematical model; epidemiology
1. INTRODUCTION
To date it is believed that the majority of clinical cases
of variant Creutzfeldt–Jakob disease (vCJD) in the UK
have been caused by consumption of Bovine spongiform
encephalopathy (BSE)-infected beef (Bruce et al. 1997;
Hill et al. 1997; Scott et al. 1999). Despite high
estimates of the number of BSE-infected cattle that
entered the food supply (in the order of 3–4 million
animals (Donnelly et al. 2002)), the number of cases of
vCJD has remained low with 161 cases to the end of
2005, and the annual incidence steadily decreasing since
2000. Estimates for the total scale of the epidemic
through this route have reduced over time and now lie
in the low hundreds (Clarke & Ghani 2005).
A survey of appendix and tonsil tissues (Hilton et al.
2004) estimated a much higher prevalence of infection in
the population than suggested by the clinical cases. This
finding is best explained by the hypothesis that a large
proportion (84.4%) of infections are sub-clinical (i.e. will
never go on to develop symptoms within their lifetime;
Clarke & Ghani 2005). Evidence for a sub-clinical vCJD
state has been found in animal studies (Hill et al. 2000;
Hill & Collinge 2003; Bishop et al. 2006). Infection is
detectable throughout the CNS and lymphatic system in
patients with clinical vCJD (Wadsworth et al. 2001). In
addition, the abnormal formof the prion protein (PrPSc)
has been detected in the spleen of a patient who died
from other causes (Peden et al. 2004) and in the
appendix of a vCJD case removed 3 years prior to
their death (Hilton et al. 1998). Given that infectious
PrPSc is detectable in patients showing no clinical
symptoms, it is possible that it could be transmitted
through surgical procedures. Surgical instruments are
decontaminated routinely before use on another patient.
However, research suggests that PrP binds strongly to
stainless steel and that current sterilisation procedures
are unlikely to be effective because of the high
temperatures required to deactivate PrPSc (Flechsig
et al. 2001; Yan et al. 2004). Furthermore, a survey of
decontamination practices has shown that past practices
fell short of the expected standard in many hospitals
(Estates 2000). Although steps have been taken to
improve the situation (Estates 2001), it is likely that the
reality of decontamination is still less than perfect and
hence that residual infectivity will remain.
J. R. Soc. Interface
doi:10.1098/rsif.2006.0142
Published online
*Author for correspondence ([email protected]).
Received 22 May 2006
Accepted 21 June 2006 1 q 2006 The Royal Society
snip....
full text ;
http://www.journals.royalsoc.ac.uk/media/7hxdahxwvm0wxxrrvbfk/contributions/8/0/v/8/80v81437446nu2m5.pdf
NOT TO FORGET THE SPORADIC CJDs ;
Transmission of Creutzfeldt-Jakob disease to a chimpanzee by electrodes contaminated during neurosurgery.
Gibbs CJ Jr, Asher DM, Kobrine A, Amyx HL, Sulima MP, Gajdusek DC.
Laboratory of Central Nervous System Studies, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Stereotactic multicontact electrodes used to probe the cerebral cortex of a middle aged woman with progressive dementia were previously implicated in the accidental transmission of Creutzfeldt-Jakob disease (CJD) to two younger patients. The diagnoses of CJD have been confirmed for all three cases. More than two years after their last use in humans, after three cleanings and repeated sterilisation in ethanol and formaldehyde vapour, the electrodes were implanted in the cortex of a chimpanzee. Eighteen months later the animal became ill with CJD. This finding serves to re-emphasise the potential danger posed by reuse of instruments contaminated with the agents of spongiform encephalopathies, even after scrupulous attempts to clean them.
PMID: 8006664 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8006664&dopt=Abstract
TSS