Avian Bornavirus Neurologic Disease in Macaws

Avian bornavirus neurologic disease is a serious viral condition that affects the nervous system of parrots, including macaws. It is closely linked to proventricular dilatation disease (PDD), which many pet parents also know as macaw wasting disease. The virus has a strong attraction to nerve tissue, so signs may involve the digestive tract, the brain and spinal cord, or both.

In many birds, the earliest changes are subtle. A macaw may lose weight despite eating well, regurgitate, or pass whole seeds in the droppings because the nerves that help move food through the digestive tract are inflamed. Other birds show more obvious neurologic changes, such as tremors, weakness, poor coordination, vision changes, or seizures.

One confusing part of this disease is that some birds carry avian bornavirus without looking sick. That means a positive test does not always equal active disease. When clinical disease does develop, it is often progressive and can become life-threatening, so early evaluation by your vet is important.

The underlying cause is infection with psittacine bornavirus, commonly called avian bornavirus. In parrots, this virus is associated with inflammation of nerves in the digestive tract and central nervous system. That inflammation is what leads to the classic signs of PDD and neurologic disease.

Macaws are one of the species most often associated with this condition, although other parrots can be affected too. The virus is considered contagious, but transmission is still not perfectly understood. It is thought to spread through exposure to infected droppings, urine, saliva, nasal secretions, or contaminated environments. Shedding can be intermittent, which makes flock control harder.

Another challenge is that infection and disease are not the same thing. Some birds test positive and remain outwardly healthy, while others go on to develop progressive illness. Stress, immune response, viral strain, and individual susceptibility may all play a role, but your vet usually cannot predict with certainty which exposed bird will become sick.

Diagnosis usually starts with a careful avian exam and a review of your macaw's weight trend, droppings, appetite, and neurologic changes. Your vet will often recommend baseline blood work and whole-body radiographs. If digestive involvement is suspected, contrast imaging with barium may help show an enlarged proventriculus or delayed movement of food.

Specific testing often includes PCR for avian bornavirus using blood and/or choanal and cloacal swabs. These tests are useful, but they are not perfect. A bird may test negative if it is not shedding virus at that moment, and a positive result may reflect infection without active clinical disease.

In some cases, your vet may discuss a crop or proventricular biopsy to look for the characteristic inflammatory nerve lesions on histopathology. This can add stronger evidence, though false negatives still happen because lesions may be patchy. If a bird dies, necropsy with tissue sampling from the crop, proventriculus, ventriculus, and brain is often the best way to confirm the diagnosis and guide decisions for other birds in the home or aviary.

Prevention centers on biosecurity and careful bird introductions. New birds should be quarantined in a separate airspace when possible, handled after your resident birds, and evaluated by your vet before any contact. Because infected birds may shed virus intermittently and may not look sick, quarantine should be meaningful, not just a few days in another cage.

Good hygiene also matters. Clean food and water dishes daily, remove droppings promptly, and disinfect cages and surfaces with products your vet recommends for bird-safe use. Avian bornavirus is thought to be susceptible to heat, dryness, and many disinfectants, but cleaning must be consistent to reduce risk.

If one bird in the home tests positive or develops confirmed disease, your vet may recommend separation from other birds, repeat testing, and close monitoring of exposed flockmates. There is no widely used preventive vaccine for pet macaws, so prevention depends on screening, quarantine, sanitation, and avoiding unnecessary mixing of birds from unknown health backgrounds.