A104 - Avian polyomavirus

Avian polyomavirus (formerly budgerigar fledgling disease virus or papovavirus) infection is caused by a 40-50-nm-diameter virus containing double-stranded DNA genome. It has a woldwide distribution and is one of the most significant pathogens of caged birds. Polyomavirus is highly infectious and may be able to infect most, if not all, of the parrot species, although most infections are unapparent. Disease predominates in nested macaws, conures, eclectus parrots, ring-necked parrots, lovebirds, and budgerigars and has been infrequently documented in other species. Disease in adult birds is rare and may require a simultaneous infection with the Psittacine Beak and Feather Disease Virus.

Viremia may develop as soon as 9 days in the budgerigar but may take as long as 2 weeks in other species. Soon after the development of viremia, virus can be detected in cloacal swabs. In nonbudgerigar parrats, the correlation between blood and cloacal viral DNA is complex. In cockatoos and conures, blood viral DNA was consistently present, whereas cloacal viral DNA was only intermittently present in some birds. Nestlings of most parrots shed virus for up to 16 weeks, whereas adult birds may shed virus for only 6 weeks or less.
Based on the most resent studies, HealthGene recommends the following testing procedures. For screening individual birds without a history, PCR analysis of the blood should be done. If the bird is positive and an adult, it should be re-tested in 4 to 6 weeks. If it is a juvenile bird, it should be re-tested in 12 to 16 weeks. If the bird is negative on the blood second test, an additional test should be done on a cloacal swab to make certain that it is no longer shedding virus in the droppings. If nestlings or adult birds have a known exposure to polyomavirus, immediate testing of these birds generally shows that the birds are infected and actively shedding the virus. Rather than spend the client’s money at this point, it will be more meaningful to wait 12 to 16 weeks after exposure and use the PCR assay for blood and cloacal swab.
One concern is the possibility that after vaccination birds might be transiently positive by blood PCR with viral DNA from the vaccination. Preliminary trials have shown that viral DNA is not present in the blood of birds after vaccination for polyomavirus. Veterinarians must therefore conclude that if a bird’s blood is positive by PCR, regardless of whether it is vaccinated, it is infected with polyomavirus and is most likely shedding the virus.