Parrot Bornavirus & Proventricular Dilatation Disease

Proventricular Dilatation Disease PDD, is a significant cause of disease and death in captive parrots and some wild birds. Our major task is to learn more about this virus and to seek new methods to prevent, diagnose, and treat the diseases caused by this virus.

Proventicular Dilation Disease (PDD) was first described in macaws, such as the Scarlet Macaw (Ara macao) above. Picture: The Macaw Society

PDD was first described in the late 1970s in young macaws imported from the Santa Cruz area of Bolivia and that is why was originally called “Macaw Wasting Disease”. It is suggested that it was a new disease in macaws and other large psittacines species because of its high lethality.  Today, it has been found in over 50 different species of psittacines and a number of other birds from canaries to waterfowl. Unfortunately, there is no effective cure for PDD research continues to look for more effective ways to mitigate, slow, or prevent the development of GI or neurological symptoms of PDD/AGN

The name PDD comes from a common clinical outcome: dilation of the proventriculus (widening of the region of the stomach between the crop and the gizzard). This dilation is caused by accumulated food due to partial paralysis of the digestive system. ABV infections can affect multiple body systems including the central nervous system and the GI tract.  Other conditions can mimic some or all of the symptoms of PDD.  While some ABV infected birds develop PDD, many birds who test positive for ABV do not develop any symptoms.  It is currently unknown what triggers disease progression after infection and continues to be an area of active research investigation


The Psittacine Bornaviruses are a family of viruses found worldwide. Since their discovery, it has become clear that they are common in captive parrots but do not necessarily cause disease.

The virus is not highly resistant to environmental degradation. Schubot Center research under the leadership of Dr. Jeffrey Musser have shown that it can be readily destroyed by drying. It also appears to be susceptible to destruction by commonly employed disinfectants.

Vaccination against this virus is being studied at the Schubot Center at the present time. It is too soon to say whether this will be successful but preliminary studies with some innovative new vaccines have yielded encouraging results.

Back in 2010, these studies were initially undertaken by Dr. Susan Payne and her graduate student Samer Hameed as well as Dr. Musser’s graduate student Tariq Hantash.

Since June 2021, Dr. Caitlin Mencio has joined our research team as an Assistant Research Scientist thanks to the generosity of the Pat Palmer Foundation and the support of the Schubot Endowment. Dr. Mencio is currently leading the Schubot Avian Borna Virus 9ABC) research team. Her research will be focused on virus transmission, disease diagnosis, and vaccine development.  She is particularly interested in the molecular basis for ABV infection and the progression from infection to clinical symptoms of PDD


Severe PDD lesions in the ventriculus of experimentally infected cockatiels. Research by Schubot ABV research team in 2010. (Picture Courtesy of H.L. Shivaprasad.) 10.1016/j.cvex.2010.05.014

There are two ways to diagnose viral infections. One is to look for the virus itself, the other is to determine if a bird has made antibodies to the virus. We have been able to detect Bornaviruses in bird droppings. Dr. Heatley’s studies have shown that the virus infects the bird’s kidneys and hence is spread in the urine (the white portion of a bird dropping). Not all birds, however, develop kidney infections and hence do not always shed the virus in their urine. Thus this is not an ideal test. We have been investigating antibody-based tests for detecting infected birds and are obtaining encouraging results with modern rapid testing technology. Watch this space for new results as we get them.


Bornaviruses are the cause of much suffering in birds and it is essential that we seek ways of treating sick birds. Both Dr. Hoppes and Dr. Musser are investigating drugs that might destroy the avian bornavirus or somehow stop the progress of the disease. Results to date are mixed but we will continue to support this approach.


While disease in captive birds is our main focus, we have also investigated the presence of these viruses in wild birds. Thus Waterbird bornaviruses occur in about 25% of mute swans, 15% of geese and 10% of wild ducks in this country (it’s also present in domestic ducks). Current evidence suggests that these viruses do not transfer between waterbirds and parrots. There is no evidence that the avian bornaviruses can infect mammals.

Schubot Center researchers have been studying this disease and the virus that causes it for many years. This web site is designed to keep you up-to-date with our recent research information.

Vaccination against this virus is being studied at the Schubot Center at the present time. It is too soon to say whether this will be successful but preliminary studies with some innovative new vaccines have yielded encouraging results.

Answers to Frequently Asked Questions about PDD and Parrot Borna Virus