Avian Polyomavirus Infection in Macaws

Avian polyomavirus is a contagious viral disease of parrots and other birds. In macaws, it matters most in chicks, recently weaned babies, and young birds, because they are more likely to become seriously ill. Adults may look normal but still test positive for a period of time and spread the virus to other birds.

This infection can move fast. In young psittacine birds, signs may appear about a week after exposure and can progress from vague illness to collapse within a day or two. Some birds show digestive signs like crop stasis and poor appetite, while others develop bruising, bleeding problems, abnormal feathers, or sudden death.

For pet parents, the hardest part is that polyomavirus does not always look dramatic at first. A baby macaw may only seem quieter, less interested in feeding, or slower to empty the crop. Because the disease can worsen quickly, any sick young macaw should be seen by your vet right away.

Avian polyomavirus infection is caused by a virus in the family Polyomaviridae. The virus spreads between birds through direct contact and through contaminated droppings, feather dust, crop secretions, food bowls, water dishes, hand-feeding tools, cages, and nest environments. People can also move the virus between birds on their hands, clothing, shoes, or equipment.

Macaws are at higher risk when they are very young, stressed, crowded, being hand-fed, or entering a home or aviary with birds of unknown testing history. Breeding collections, nurseries, pet stores, bird fairs, and homes that add new birds without quarantine can all increase exposure risk.

Adult birds often handle infection better than babies, but that does not make them harmless. A healthy-looking adult can shed virus for weeks to months after exposure. That is why your vet may recommend testing and quarantine even when no bird in the household appears sick.

Diagnosis usually starts with a careful history and exam. Your vet will want to know your macaw's age, whether the bird is hand-fed or recently weaned, any contact with new birds, breeding or nursery exposure, and whether there have been sudden deaths in the household or aviary.

The most common antemortem test is PCR (DNA) testing on whole blood and/or oral or cloacal swabs. In many cases, your vet may recommend more than one sample type because viral shedding can vary. Testing may be paired with a CBC and chemistry panel to look for anemia, inflammation, dehydration, liver involvement, or other clues that help guide supportive care.

Because polyomavirus can look like other serious bird diseases, your vet may also discuss testing for conditions such as psittacine beak and feather disease, chlamydiosis, avian bornavirus, bacterial infection, or fungal disease. If a bird dies suddenly, necropsy with tissue testing can be the most useful way to confirm the cause and protect other birds in the home.

Prevention starts with strict quarantine and screening. Any new bird should be kept separate from resident birds until your vet has examined the newcomer and discussed appropriate testing. This matters even when the new bird looks healthy, because adult birds can carry and shed polyomavirus without obvious signs.

Good hygiene also makes a real difference. Clean food and water dishes daily, and disinfect cages, perches, nursery tools, and hand-feeding equipment regularly with bird-safe methods. Avoid sharing bowls, syringes, towels, or toys between birds unless they have been thoroughly cleaned and disinfected. If you handle multiple birds, wash your hands and change clothing or use dedicated care supplies between groups.

If you breed macaws or keep multiple parrots, ask your vet about flock-level prevention. Merck notes that vaccination is used in breeding birds, with two doses given two weeks apart in the off-season. Your vet can help decide whether testing, quarantine, vaccination, or a combination is the best fit for your birds and your setup.