Encephalitis and Encephalomyelitis in Macaws

See your vet immediately if your macaw shows neurologic signs. Encephalitis means inflammation of the brain. Encephalomyelitis means inflammation of both the brain and spinal cord. In a macaw, that inflammation can disrupt balance, vision, coordination, grip strength, swallowing, and normal behavior.

This term describes a pattern of disease, not one single diagnosis. In parrots, neurologic inflammation may happen with viral disease, severe infection elsewhere in the body, toxin exposure, immune-mediated inflammation, or other serious illness. One important macaw-related condition is avian bornavirus infection, which is associated with proventricular dilatation disease and has also been described as psittacine encephalomyelitis or avian ganglioneuritis. Some birds have digestive signs, some have neurologic signs, and some have both.

Because birds often mask illness, even mild wobbliness or unusual quietness can matter. A macaw that is falling, trembling, or having seizures needs urgent avian veterinary care. Early supportive care may improve comfort and can give your vet more options while testing is underway.

In macaws, one of the best-known infectious associations is avian bornavirus. Merck notes that bornavirus-related proventricular dilatation disease was first recognized in macaws and may cause neurologic signs such as tremors, weakness, ataxia, convulsions, and blindness, sometimes with regurgitation, weight loss, or whole seeds in the droppings. This condition has also been called psittacine encephalomyelitis. Not every infected bird looks the same, and some birds may shed virus intermittently.

Other possible causes include other viral infections, severe bacterial or fungal infection that spreads to the nervous system, inflammatory disease, and systemic illness that secondarily affects the brain. Neurotropic viral diseases in birds can also produce weakness, paralysis, and tremors. In practice, your vet may also need to rule out heavy metal toxicity such as lead or zinc, because toxicosis can cause seizures, weakness, GI upset, and other signs that mimic primary brain disease.

Less common but still important differentials include trauma, vascular events, nutritional problems, and tumors affecting the brain or spinal cord. Because the list is broad, home treatment is not enough. The safest next step is a prompt avian exam so your vet can narrow the cause and discuss realistic care options.

Diagnosis starts with a careful history and hands-on avian exam. Your vet will ask when the signs started, whether they are getting worse, what your macaw eats, whether there has been access to metal, fumes, new birds, outdoor mosquito exposure, or recent stress, and whether there are digestive signs like regurgitation or undigested food. Baseline testing often includes a complete blood count, chemistry panel, and whole-body radiographs to look for infection, inflammation, organ disease, metal density, or an enlarged proventriculus.

If bornavirus-related disease is suspected, VCA notes that PCR testing can be performed on blood and choanal or cloacal swabs, and your vet may discuss crop or proventricular biopsy for histopathology. These tests can help, but false negatives can happen, so results must be interpreted with the exam findings and imaging. In birds that die or are euthanized, necropsy with tissue sampling from the crop, proventriculus, ventriculus, and brain is often the clearest way to confirm the diagnosis.

Your vet may also recommend targeted testing for toxins or other infections based on your bird's history and exam. In unstable birds, treatment often begins while testing is still in progress. That is common in avian medicine and does not mean the workup is incomplete. It means your vet is balancing speed, stress, and safety.

Prevention starts with reducing exposure to infectious disease and toxins. Quarantine any new bird before introduction, avoid sharing bowls or perches between birds during quarantine, and keep cages, food dishes, and surrounding surfaces clean. Because avian bornavirus may be shed in feces and other secretions, good hygiene and separation of sick birds matter. If one bird in the home develops neurologic or unexplained digestive signs, ask your vet how to protect the rest of the flock.

Lowering toxin risk is also important. Keep your macaw away from loose metal objects, galvanized wire, peeling hardware, lead weights, jewelry, and unsafe household items that can be chewed. Avoid smoke, overheated nonstick cookware fumes, aerosolized chemicals, and other airborne irritants. Feed a balanced diet recommended by your vet, and schedule routine wellness exams so subtle weight loss or behavior changes are caught earlier.

You cannot prevent every case, especially when the exact cause is unclear. Still, early recognition is one of the most powerful tools pet parents have. A macaw that suddenly seems weak, clumsy, unusually quiet, or unable to perch should be seen promptly. Fast action can improve comfort, shorten delays in diagnosis, and help protect other birds in the home.