1. The possum is a pest that was introduced (Can't remember how) Our other Marsupials are Koalas,Kangaroos,The Wallaby,Wallaroo,Platypus etc.
2. Not all Australians are "Pisspots",Drunks or Alcoholics. I'd say the girl that was spoken about must have spent time in the Northern Territory or out in the western parts where there is little else to do supposedly.
3. No as far as I know we don't have any Tests for BSE, there probably are tests especially if an animal is behaving unusually. I have no experience with any tests.