Central Nervous System Viruses

Neurologic/neurotropic viruses of the avian species maybe the problem

I have a 7-year-old Moluccan cockatoo that has neurological signs. She acts like she is drunk ?falling off perches, trembling, holding her head crooked and showing poor feather condition. My veterinarian tested her with X-rays, blood work and a crop biopsy for Proventricular Dilatation Disease (PDD). All the tests have come back negative. She also tested negative on a heavy metal blood profile. Do you have any idea what her problem may be?

What you describe sounds like one of the neurologic/neurotropic viruses of the avian species. There are several of these. We know something about some of them, but absolutely nothing about others. I think there are many of these viruses that we do not even have names for yet. I will tell you about those I know.

Eastern Equine Encephalomyelitis
This virus has been known about for many years, and a bird can serve as a reservoir host, most often subclinically, that is not showing signs of disease. As the name implies, this virus can cause encephalomyelitis in horses. A vaccine is available for equines, which I believe is rather effective in that species. Vectors, like mosquitoes, transmit this disease. Those of us who like to take our birds outside may put them at risk from mosquito bites. Although the University of Georgia has definitive testing by PCR analysis for this viral disease, it is usually found at autopsy.

This group of viruses can present in many different ways in avian species. The most known about and most publicized paramyxovirus is the one that causes PDD. This disease is more correctly named neuropathic ganglioneuritis. This paramyxovirus affects the nerve ganglia of the gastrointestinal tract, most often causing proventricular and ventricular dilation. A crop biopsy, serum sample and fecal sample are the test samples of choice for a veterinarian to submit to the University of Georgia for screening of this virus. A negative test means nothing, a positive test means your bird is infected.

Other Paramyxoviridae appear to be the most common cause of the encephalomyelitis infections. These viruses affect the ganglia and blood vessel walls in the brain and spinal cord. Basically, a bleed occurs in the brain or spinal cord, and the blood damages adjacent tissues and destroys the proper nerve transmission capabilities of the surrounding tissues. This is similar to a stroke in a human. The location where the bleed occurs and the extent of the damage is what dictates the severity of clinical signs. I have had patients that were “normal” one moment to the owner, the bird then lets out a loud squawk, falls off the perch in a seizure and dies. I have had birds slowly develop progressive neurological signs over a period of months before they had to be euthanized due to their pitiful condition. The scariest part is that I have had one bird in a single bird household for 25 years that developed signs and died. This says that the incubation periods of these viruses may be very long or that birds are easily exposed by vectors.

Other Dangers
There are obviously other viruses emerging on the scene that can cause these types of symptoms. What about the West Nile virus ?the one discovered by a diligent female veterinarian in New York State after noticing abnormal numbers of crows dying. This virus has now been found in Florida, Georgia, Alabama and, as of last week, in Marion County, Indiana, which is not far from my home. I expect I will be seeing it shortly if I have not already seen it and just been too ignorant to diagnose it. This virus causes encephalitis in humans and has been responsible for several human deaths. Watch out for the mosquitoes ?they are the culprits, not the birds!

I hope I have answered your questions as to what the problem may be in your Moluccan. I am sorry that I have not been able to tell you about cures for these viruses, the fact is that there are none.

Thanks for your question.

Sam Vaughn, DVM, Dip., ABVP ?Avian Practice is an avian specialist based in Louisville, Kentucky. Certified in Avian Practice by the American Board of Veterinary Practitioners, Dr. Vaughn owns Avian Medical Services Inc. (an avicultural service and consultation practice) and is a partner in Veterinary Associates Stonefield, a full-service avian/exotic and small animal practice. Dr. Vaughn holds degrees in biology, chemistry and a Doctorate of Veterinary Medicine from Auburn University. Feel free to visit his web site at http://www.vetcity.com. Telephone consultations by appointment are available by calling (502) 245-7863.

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