Polyomavirus

Avian polyomavirus is a contagious viral disease of parrots that is most dangerous for young birds in the nest and birds about to be weaned. In budgerigars it can cause sudden deaths of the young, and birds that survive are often left with permanent feather changes known as French moult. Adult birds usually show no signs of disease but can spread the virus.

The disease is caused by avian polyomavirus. It can infect almost all parrot species and occurs most often in breeding stocks of budgerigars, cockatiels, lovebirds, cockatoos, macaws and conures.

The virus spreads:

• through the droppings, dander and feather dust of infected birds;
• through crop secretions when parents feed their young;
• through contaminated dishes, cages, nest boxes and hands;
• in hand-rearing rooms, where chicks from different breeders are mixed.

The virus is very resistant and can survive in the environment for a long time. After infection, adult birds mostly remain without symptoms, but they shed the virus from time to time, especially under stress and during breeding.

In young budgerigars (in the nest, up to about three weeks old):

• sudden deaths of the young, often without any previous signs;
• a swollen abdomen and slow crop emptying;
• reddened skin and bleeding under the skin;
• trembling of the head and neck;
• delayed growth of down and feathers.

In young larger parrots (around weaning):

• sudden weakness, loss of appetite and loss of interest in the surroundings;
• crop stasis and vomiting, diarrhoea;
• bleeding under the skin and prolonged bleeding from feathers or small injuries;
• difficulty breathing in the severe form;
• death often occurs within one to two days.

In budgerigars that survive (French moult):

• the flight feathers of the wings and the tail feathers do not grow, or fall out and break easily;
• the plumage is untidy, and bald patches may remain on the back and belly;
• the bird cannot fly, so it runs around on the cage floor.

Most adult birds have no visible symptoms even though they are infected.

• The death of one or more young in the nest for no clear reason.
• A chick with a swollen abdomen, red skin or bruises.
• A crop that does not empty, vomiting or refusal of food in a chick.
• Bleeding from a feather or injury that does not stop.
• Sudden weakness and sitting with ruffled feathers in a young parrot.

If a chick has died, put it in a sealed bag in the fridge (not the freezer) and take it to a vet. Examining the dead bird is often the quickest way to find the cause and protect the other chicks.

The vet takes blood samples and a cloacal swab for a PCR test, which detects the virus. In dead birds the diagnosis is confirmed by examining and testing the organs. Feather changes similar to French moult can also be caused by PBFD (psittacine beak and feather disease), so both diseases are usually checked at the same time.

If one bird in a breeding stock tests positive, the vet will usually recommend testing all the birds, as adult carriers of the virus mostly look completely healthy.

There is no medicine for polyomavirus that destroys the virus. Treatment is supportive: warmth, fluids, help with feeding and treatment of secondary infections with medication prescribed by the vet. In the severe form in young birds the outcome is unfortunately often poor.

First aid and care:

• separate the sick bird from the others in a separate room;
• provide a warm, dark and quiet place without draughts;
• do not push food into the beak or pour in water – have the vet show you how to feed the chick;
• after handling the sick bird, wash your hands and change your clothes before going near the others.

Budgerigars with French moult can live a comfortable life. In some the feathers partly grow back over time, while others never fly. Adapt the cage for such a bird: low perches, ladders and soft flooring, with food and water within reach.

Polyomavirus is not dangerous to humans.

• Keep new birds separate for at least a month and have them tested by a vet before putting them together.
• Do not bring birds from shows and fairs straight into the breeding room.
• Do not mix chicks from different breeders during hand-feeding.
• Clean cages, nest boxes and dishes regularly and remove feather dust.
• After an outbreak, vets often advise stopping breeding for several months and thorough disinfection.
• Reduce stress: enough space, good nutrition and clean air strengthen birds' resistance.

Polyomavirus is most dangerous for young budgerigars and parrots, while adult birds can carry it without signs of disease. Quarantine, testing new birds and good hygiene are the best protection for a breeding stock, and whenever young birds die for no apparent reason, contact a vet.