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Saving parrots from killer disease
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This is the second part of a two-part story on Avian Borna Virus and the disease it is thought to cause, Proventricular Dilatation Disease. PDD is a fatal avian disease first discovered in the 1970s. It's estimated to affect approximately 50 species of birds, including some rare and very valuable parrots, such as the critically endangered Spix's Macaw and Blue Throated Macaw. Avian Borna Virus (ABV) was identified as the suspected cause of the disease last year. There is now a blood test and a fecal test to detect the virus.
Dr. Ian Tizard is Professor of Exotic Bird Health and Professor of Immunology at the Schubot Exotic Bird Health Center at Texas A&M University. He is also the center's Director. Tizard and his team of researchers have been working on the virus and PDD since 2007.
“It's clear that (some) birds can be infected with this virus for a long time,” Tizard said. "It can get sick and recover for months or even years, then it gets sick again. We don't know what's triggering these relapses. We've had several relapses in our birds where we are monitoring them closely and the bottom line is some get sick for no apparent reason,” Tizard said.
Depending on a bird's symptoms and the severity, it's possible that with medication, very close monitoring and some TLC, a bird can recover for a period of time. That's not necessarily so of all birds with PDD. When a birds tests positive for the virus, it's not an immediate death sentence. It does not mean the bird will develop the full blown disease and die right away. There is no way to tell how long it will live with the virus before it develops symptoms and then the disease. What's also very troubling is when a pet bird is discovered to have ABV without ever having been obviously exposed.
“There are stories of birds that live by themselves for 10-15 years and then come down with PDD with no obvious contact to other birds," Tizard said, "so I assume that some infected birds can remain healthy for a long period of time. The thing is, was there truly no exposure, or are we talking about exposure a long time ago?”
“In classical PDD involving the intestine, it appears that Avian Borna Virus destroys the nerves leading to the intestine. This results in paralysis, blockage of the flow of food, failure to absorb nutrients, starvation and death. The eventual cause of death is probably destruction of brain cells. We also see cases with damage to the nerves leading to the heart possibly leading to heart failure. We certainly see cases affecting the optic nerve and eye resulting in blindness.” Tizard said.
“I think every bird infected with this illness has the virus in both the brain and in the nerves that lead to the intestine, and what the clinical signs are probably depend in large part to precisely what part the nervous system is affected.”
Signs of illness
Symptoms of PDD include weight loss, lethargy, vomiting, loss of balance, seizures, and passage of whole seed in the feces. However, these symptoms appear in more than one illness, so if your bird has any of the symptoms, call your vet right away. Birds will often hide symptoms of any disease until they are too sick to hide it any longer. By then it could be too late.
Fecal tests, blood tests, and removing and testing a small part of a bird's crop are methods scientists use to test for the virus. Dr. Tizard's team has found their blood test – not currently available to the public - shows a positive reading when the bird get sick. It does not, however, show a positive when the bird has the virus but is not yet sick. The fecal test offered by the Schubot Center gives a reading far sooner than the blood test. The fee is currently $30.
Crop biopsies are not 100 per cent accurate and are an invasive procedure many owners won't even consider. Examining and testing the body after death is the only way to determine for sure if a bird had PDD. Not all birds with PDD suffer from the same symptoms.
The name Proventricular Dilatation Disease is, in a sense, a misnomer, Tizard said.
“It's clear that some birds do get proventricular dilatation. But some birds, like African Greys, seem to get purely neurological signs and many of them don't have many gut lesions at all,” Tizard said. Stomach lesions are a classic symptom of PDD. Those lesions interfere with the digestion of food.
“The clinical signs are highly, highly variable...so we're calling it Avian Borna Disease. “I am beginning to suspect that the disease has more and different manifestations than we suspected.”
Currently there is no vaccine against AVB. The Schubot Center at A&M is part of a multinational groups that's looking at immunosuppressant medications to see if they can help. Birds who have Avian Borna Virus and PDD are being treated with anti-inflammatory drugs like Celebrex.
Tizard says researchers will try to make a vaccine, but “there's a significant chance a vaccine could make the disease worse.”
“It is well recognized that in some number of cases of viral infections of the nervous systems, it isn't the virus that does the harm, it's the immune response that attempts to eliminate the virus that causes the problem.”
Protecting your birds
Because there is no vaccine and no cure for PDD, the next best thing is to practice strict hygiene when around infected birds. “People who have infected birds in their collection need to think of this an an infectious agent, practice good hygiene, practice biosecurity and stop the spread of the virus. They need to identify who has got it and who hasn't, separate them out, and keep their clean birds clean. Likewise, if bringing in a new bird, get it tested for ABV before it comes in.” Tizard said birds should also be very carefully tested for Pacheco's disease and Psittacosis.
To protect your birds against getting any easily transmittable virus, be very cautious when visiting pet shops where birds are sold. Responsible pet stores will test all their birds for ABV and other illnesses and will be glad to tell you about their care policies and procedures. Reputable breeders will do the same. To protect your own birds, don't handle birds whose history and background you don't know. Wash your hands after before and after handling birds that are not your own.
Other precautions to take with ABV infected birds: make sure not to transfer fecal matter from one bird or bird cage to another since ABV can be spread through feces. Do not interchange food and water bowls among birds and use separate cleaning materials for each bird. Wash your hand thoroughly between cleaning up after each bird. Don't expose your birds to other birds you don't know.
Some vets suggest taking the same preventative methods that are recommended to avoid the spread of Exotic New Castle's disease in birds. Before and after you visit birds or bird stores outside your home, those steps include showering, changing clothes, removing shoes and disinfecting them and anything else that was exposed before you handle your own birds. Prevention is best. Don't go near sick birds or where there may be sick birds.
As with Exotic New Castle's disease, fastidious hygiene practices are necessary to prevent the spread of the ABV. Tizard's belief is that the methods to disinfect after being exposed to New Castle's Disease will also work for disinfecting after exposure to PDD. Refer to the University of California's site for recommended methods for disease control. http://animalscience.ucdavis.edu/avian/disease_control.htm.
“ABV has spread fairly easily through our aviary. I think it is quite a contagious virus,” Tizard said. “I think it is quite a commonplace virus from places we're able to find it.”
Ongoing Research
Researchers are trying to determine if the virus is airborne. If it is, that presents a real challenge to owners who may not have the room to separate their flock.
“Treatment and prevention are now the areas we are focused on,” Tizard said, adding that the Schubot center has disinfectant studies underway.
It's not known for certain if the virus is long lived outside a bird's body or how hardy the virus is. For all that is known about ABV and PDD, so much more is not yet known. That's all the more reason for bird owners to be vigilant. Early detection is absolutely necessary if an infected bird is able to have a good quality of life, even it it's infected with the virus. An infected bird will need medication, but it may continue to enjoy a good quality of life even with the virus.
“I know there are a lot of questions right now but what it boils down to is how do we control this wretched disease? Right now my belief is that if it's done right, what will work is management,” Tizard said. “Manage your aviary in a way that you don't purchase birds that are positive for ABV. If your aviary is clean, you keep it that way and if your aviary is infected, you separate off those birds – don' t euthanize them – but manage them separately, as if you have two collections, and try to keep it that way. Let your infected birds live out their lives and try at the same time to build a clean aviary.”
The discovery of the Avian Borna Virus and the development of tests to detect it are major achievements in the fight against this cruel and fatal disease.
“Our knowledge base has increased dramatically and now we can start trying to control the disease rationally, ” Tizard said.
“We've cracked open the lid and we can see what we're dealing with, but we haven't saved a bird yet and that's the bottom line.”
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