PBFD is caused by a circovirus which kills the cells of feathers and the beak. It is a naturally occurring infection in Australian cockatoos but it is found in all types of parrots as well as lovebirds, cockatiels, budgies and parakeets. African greys are particularly badly affected. PBFD is a dreadful disease which normally results in the death of affected birds and the decimation of young birds in infected collections. Chronically affected birds become immunosuppressed and may succumb to other diseases due to their depressed immune system. A positive result from a bird with no feather problems or other clinical signs may mean either that the bird is a carrier or that it has been recently exposed to the virus. In these cases we recommend isolating the bird and re-testing in about 90 days. We also recommend that the second sample is collected directly from a vein by venipuncture to avoid contamination. The majority of birds which are merely exposed will develop an immune response and eliminate the infection. Those still positive at the second test should be considered as carriers. One day they are likely to show the disease, and become potential source of infection to other birds.

Avian Polyoma (also known as Budgerigar Fledgling Disease) is most prevalent in macaws, conures, eclectus parrots, ring-necked parrots, lovebirds, cockatiels and budgies although it occurs in all psittacine species. It is most commonly recognised in chicks in the nest. Swollen bellies, tremors, weak wobbly chicks, or abnormal feathers may be seen. Larger psittacine species may live longer and show diarrhoea or regurgitation. Classical infections seem to affect larger species at around 7 weeks of age and can kill within a few hours of the first signs with chicks showing large bruise-like haemorrhages under the skin. Adult birds are also affected. Signs resemble those of septicaemia and hepatitis. Some infected adult birds may not show any signs but may become carriers shedding the virus Embryonic death or decreased hatchability can also be caused by Polyomavirus. Polyoma is transmitted primarily bird to bird but it is also thought to be transmitted via the egg.