Avian Pox:
A Curse For Afflicted Birds

by Stephanie Streeter

from DVRC Journal Fall/Winter 95

Raptor rehabilitation centers seldom treat birds that are suffering solely from diseases contracted in the wild. That's not to say that there aren't some nasty diseases out there that raptors can fall victim to. There are, and they can be bacterial, viral, fungal or parasitic in nature. However, sick hawks are not as readily found as injured ones because diseased birds tend to tuck themselves away in the woods where they quietly die, while injured hawks remain where they've fallen, usually by the roadside.

Despite this fact, some sick birds have made their way to the Delaware Valley Raptor Center, and some have been infected with the viral disease avian pox. Like childhood chicken pox, which scores of us scratched our way through in spite of our mother's scolding, avian pox produces raised, oozing (when infected) lesions. The avian poxvirus is actually part of a larger family of poxviruses that include the human disease, smallpox. On afflicted birds, lesions typically appear on the exposed (unfeathered) areas of the face, legs and feet. There is another, much less common form of avian pox that infects the respiratory and/or digestive tract. Mortality with this strain of the virus can be as high as 50%.

Our latest avian pox patient, an immature bald eagle, arrived at the center on July 29, 1995. After picking the bird up at a camp in Pocono Summit, PA, rehabilitator Kathy Dubin phoned DVRC and said she had an eagle with avian pox. Although this was the first live case of the virus she had seen, she was able to identify it by the distinctive scabby, encrusted lesions on the bird's face. Kathy decided to bring the bird to the raptor center for treatment because she had never treated avian pox and, while we have, our caseload of poxvirus patients has not been staggering. Over the past fifteen years, we have seen four pox infected birds, a red-tailed hawk, a goshawk, a bald eagle, and the young eagle currently in our care. Of these birds, three survived while the fourth, the goshawk, was dead upon arrival. These low numbers illustrate just how seldom sick hawks are actually found and turned in for treatment.

Young Bald Eagle with Pox lesions
Pox lesions cover eagle's
cere (fleshy area above beak),
as well as unfeathered
flesh around eyes

Avian pox is not a rare disease, nor is it limited to raptors. It often infects domestic chickens and turkeys, and for that reason, was studied as early as 1873 by Dr. Bollinger for whom the pox inclusion bodies are named (Bollinger bodies.) It occurs worldwide and can infect waterfowl, marine birds, upland game birds and songbirds. According to Wallace Hansen writing for the Field Guide To Wildlife Diseases, published by the U.S. Department of the Interior, Avian pox is suspected as a factor in the decline of forest bird populations in Hawaii and of northern bobwhite populations in the southeastern United States.

Because the most common means of poxvirus transmission is the mosquito, outbreaks often arise on a seasonal basis. Hansen writes that limited studies show the lowest prevalence rate of avian pox in Oregon's California quail population occurs during the dry summer months. While in Florida, data show that avian pox in wild turkeys occurs in late summer and early fall, corresponding to the mosquito season. However, avian pox can show up at any time, because mosquitos are not the virus' sole means of transmission. The red-tailed hawk we treated initially showed signs of being pox infected in December, a month in the northeast more noted for snow than mosquitoes.

Pox lesions on feet
Pox lesions on eagle's feet and toes

This slow-developing disease is highly contagious and can be passed from bird to bird through physical contact. Nestlings sharing close quarters almost always share the virus. The first pox bald eagle we treated was a newly fledged youngster that came from a nest of known infected siblings. According to government statistics, immature birds are often the most frequently and severely poxvirus infected. Our experience at the raptor center bears this out. Of the four birds we treated, three were immature. The exception was the goshawk and that bird had just turned one year old when it contracted the disease. Because avian pox can be passed to birds through contact with virus-contaminated surfaces, caring for infected birds requires strict quarantine measures. After the virus has run its course, everything the sick bird has come in contact with must be thoroughly disinfected. In the continental United States the prime source of several contact transmitted outbreaks between different species occurred at winter bird feeding stations. To lessen the risk of contact transmission of avian pox, as well as other contagious diseases, bird watchers should regularly disinfect their bird feeders with a 5% chlorine bleach solution.

Although a plain bleach solution will easily decontaminate any exposed surfaces, there is no correspondingly simple treatment for infected birds. Because avian pox is a viral disease, no medication exists to directly combat it; instead, the virus must run its course while supportive medical care is given to prevent the afflicted, weakened bird from succumbing to secondary bacterial infections. Pox infected raptors in the wild often die of starvation. Sick hawks can not hunt as effectively as healthy ones, and birds with the poxvirus sometimes lose the vision in one or both eyes because of the lesions that surround and even cover them, which further hampers their hunting efforts. The young bald eagle currently undergoing poxvirus treatment at DVRC was one of the birds that almost starved to death. When found, he weighed only three pounds - bald eagles normally weigh between six and fourteen pounds, with males being lighter than females. Intravenous fluids had to be given to keep him alive. After fluids were administered, the eagle's lesions were disinfected with a betadine solution to promote drying, his eyes treated with an antibiotic ointment, and antibiotics were given via injection. His supportive therapy started at 8:00 P.M. on July 29. At that time he was very weak and his prognosis was not good. His care continued around the clock. Because DVRC staff member, Jan Rethorst currently lives at the original DVRC site where the eagle was being treated, she had the unenviable task of waking-up every four hours through the night to care for him. At midnight and again at 5:00 A.M. on the 28th, she gave him fluids. At 10:00 A.M., he was fed a small portion of chicken (3/4 ozs.) and fluid therapy was continued, his lesions were cleaned, and ointment put in his eyes. Treatment continued throughout the day, with a note on his chart that at 5:00 P.M. he was putting up more of a fight - a good sign. Because of their size and strength, eagles can be a handful, but this bird was so sick, initially, he did little more than lay in our arms. By the end of the day on the 30th, the eagle was noticeably stronger and we no longer feared we would find a dead bird when we checked on him. He still had a long way to go, but we felt much more confident about his survival. By August 8th, he was eating fish by himself and we finally discontinued administering fluids by tube. All other treatment continued. Although his lesions did not look much better at this time, he had not developed any new ones. His eyes, which could not close because of the lesions that encircled them, were still sighted. We continued to put ointment in them to prevent infection and loss of vision. According to his medical record, by August 8th, the eagle was still on antibiotics, eating well and strong enough that heavy leather gloves had to be worn to handle him. He also tried, for the first time, to evade us when we reached for him. On August 11, the eagle's chart noted - eats everything he's given, weighs 7.5 pounds (more than twice what he weighed on admittance), some scabs coming off. On August 21, the eagle was placed in a 12'x24' flight enclosure, the scabs on his feet and around his eyes were, for the most part, gone. Although lesions still occluded one of his nares (breathing passage), he looked much better and was definitely on the road to a spring of '96 release. This will be an unusual release in that the eagle will be one year old when he makes what will esentially be his first maiden flight in the wild.

His combined treatment and recovery time will be long, yet, the only legacy the eagle will take with him of his successful bout with avian pox will be one he'll never be aware of - a lifelong immunity to the disease.