Polyomavirus (PVD), sometimes also referred to as Budgerigar Fledgling Disease, is one of the most serious threats to cage birds. A member of the papovavirus family, this highly infectious disease can affect most if not all parrot species as well as other avian species. The virus seems to be most problematic among young birds between the ages 14-56 days, who will often die. Adult birds can develop a certain level of immunity.
Polyoma is believed to have an incubation period of approximately two weeks or less and the pathogen can be spread from one bird to another via feather dust, faeces, aerosols and parental feeding of chicks as well as by direct contact between birds, or contact with infected environments such as incubators and nest boxes.
Birds that are infected but do not have obvious signs of infection are often responsible for spreading the virus to an aviary. Some adult birds can show no symptoms but may be carriers.
There are a number of symptoms of the disease and affected birds may show any or all of the visible signs, including…
- Swollen abdomen
- Loss of appetite
- Weight loss
- Delayed crop emptying
- Feather abnormalities
- Haemorrhages under the skin
- Dyspnea (difficulty breathing)
- Polyuria (excessive urination)
- Ataxia (loss of muscle control/co-ordination)
Some birds die without any clinical symptoms. Adult birds may die of secondary infection from bacterial, viral, fungal or parasitic pathogen.
How is PVD diagnosed?
Diagnosis is made in the laboratory from whole blood samples and cloacal swabs when possible and is conducted via nested primer PCR testing, sequence analysis of PDV DNA and histopathology. If a sample tests positive, the suspect bird should be placed in quarantine and re-tested in 4-6 weeks. If the bird tests negative the second time, a third test is recommended.
Unfortunately, there is no known treatment for PVD at this time. A vaccine is available, however, its effectiveness in younger birds is open to question. Booster shots are required each year.
Bird fanciers can help prevent this generally fatal disease by isolating all birds shedding the disease and disinfecting all contaminated surfaces with an oxidizer such as chlorine bleach (Polyoma virus is resistant to many disinfectants).