Summary of a paper given by Dr D.Phalen at the 1998 Association of Avian Veterinarians Conference ( 1998 Proceedings p 151 ).
Avian Polyomavirus: More Pieces to the Puzzle
The avian polyoma virus has a broad host range. It’s ability to infect and cause disease in birds is dependent on the age of the bird, the species of the bird, the immune status of the bird and other poorly understood factors.
Polyoma virus exploded into aviculture in the 1980’s. Subsequent investigation indicates that it originated in Australia as 64% of White Cockatoos were found to be positive.
Polyoma virus in NON budgerigars is seen as a bleeding disease with liver death and kidney failure. Not all birds have all the symptoms as some can have a bleeding episode but have a normal liver and visa versa. Birds with a bleeding episode may be found to have no platelets (cells which aid clotting ).
Unapparent Infections
Conures: Most conure babies exposed to the disease below 4 weeks of age will die. In birds over 6 weeks an unapparent infection occurs where the baby survives but sheds the virus for 4 - 16 weeks.
Macaws: Macaws are susceptible to Polyoma virus infection up to 14 weeks; after this an unapparent infection occurs. Peak mortality in Macaws occurs between 4 - 8 weeks. Macaws with an unapparent infection may shed the virus for 4 - 14 weeks.
Eclectus: Nestling Eclectus under 14 weeks will die if exposed to the virus
Cockatoos: Cockatoos are very susceptible to the virus but very resistant to the disease. This means that the virus circulates in the cockatoo population but does not cause disease that you can see.
Polyoma Virus Spread:
In the authors experience one or more of the following events have nearly always been associated with outbreaks.
1 - Exposure to older birds, especially nestlings at a bird shop. Bird club meeting or bird show.
2 - Introduction of nestlings from another aviary into the nursery.
3 - Introductions of nestlings into a poorly managed pet shop.
4 - The presence of Beak and Feather disease virus infected birds on the premises
5 - Exposure to Polyoma virus shedding cockatiels, lovebirds or budgerigars.
Because so many birds are unapparently infected with Polyoma virus when nestlings are brought together from multiple sources, the unapparently infected birds infect susceptible chicks.
Budgerigars, cockatiels and lovebirds have high rates of infection but low rates of disease ( like the cockatoos ) so in mixed collections they can be the source of the virus.
Beak and Feather Disease and Polyoma virus often infect the same bird at the same time - many Beak and Feather infected birds are also shedding Polyoma virus. It appears that adult birds are resistant to the Polyoma virus UNLESS their immune system is weakened by the Beak and Feather virus.
Testing for Polyoma virus is available but is quite expensive and unfortunately the results must be interpreted very carefully.
A vaccine is available to protect nestlings from the disease. The vaccine has the potential to protect susceptible chicks from infection and disease in the window of 9 - 14 weeks. Unfortunately this does not protect the nestlings during the peak mortality periods of 4 - 9 weeks.
If you think you have Polyoma virus in your birds you need veterinary help – contact your avian veterinarian immediately.