Why We Should Not Treat For Pigeon Pox

September 17, 2010

here is a good reason for us pigeons men not to treat for pox by this by all means treat with the stuff, also birds that have what a few call protein lumps are a sure sign your bird has herpes pigeon pox, but don't jag as this will only help your enemy we have the advantage here as the birds we want to save we can treat, but the birds we don't what can be of use. while in conversation with a very knowledgeable fancier, we have come up with a very interesting focal point

Description

Avian pox is a mild to severe, slow developing disease of birds caused by an avipoxvirus and three common strains have been identified. The three strains are fowl pox virus, pigeon pox virus and canary pox virus. The strains vary in their virulence and have the ability to infect other avian species. However, many of the strains are group specific. Approximately sixty species of birds from 20 families have been diagnosed with avian pox. The strain seen in wild turkeys is the fowl pox virus.

Avian pox lesions (wart-like growths) occur on the unfeathered parts of the bird's body and, in some cases, the mouth, larynx, and/or trachea.

Distribution

Avian pox has been observed in a variety of avian hosts worldwide. The disease is most common in the temperate (warm and humid) parts of the world and is usually observed in relation to seasonal mosquito cycles. Avian pox has been diagnosed in upland game birds, songbirds (mourning doves and finches), marine birds, pet birds (canaries and parrots), chickens, turkeys, occasionally raptors and rarely in waterfowl. In Michigan, it has been diagnosed in the brown-headed cowbird, American goldfinch, ruffed grouse, mourning dove, broad-winged hawk, common raven, wild turkey, trumpeter swan, bald eagle, house sparrow, American robin, European starling, sandhill crane and American crow. Avian pox has been identified in birds since earliest history but it is still currently considered to be an emerging viral disease. All North American cases have been relatively recent.

Transmission

Transmission of the avian pox virus can occur in a number of ways. The disease can be spread via mechanical vectors, primarily by species of mosquitoes (at least 10). Transmission occurs when the mosquito feeds on an infected bird that has a viremia (pox virus circulating in the blood) present or on virus-laden secretions from a pox lesion and then feeds on an uninfected bird. Mosquitoes can harbor and transmit the virus for a month or longer after feeding on an infected bird. Experimentally, stable flies have shown the capability of being able to transmit the pox virus.

Avian pox can also be transmitted by direct contact between infected and susceptible birds. The virus is transmitted through abraded or broken skin or the conjunctiva (mucous membrane covering the anterior surface of the eyeball). Indirect transmission of the pox virus can also occur via ingestion when food and water sources, feeders, perches, cages, or clothing are contaminated with virus-containing scabs shed from the lesions of an infected bird. The pox virus is highly resistant to drying and may survive months to years in the dried scabs. Indirect transmission can also occur via inhalation of pox virus infected dander, feather debris and air-borne particles.

Mosquitoes are probably responsible for transmission within local areas, while wild birds are responsible for outbreaks over greater distances.

Clinical Signs

Clinical signs observed with avian pox are weakness, emaciation, difficulty in swallowing and breathing, vision problems, a reduction in egg production, soiled facial feathers, conjunctivitis, edema of the eyelids and the presence of the characteristic wart-like growths on the unfeathered portions of the skin and/or formation of a diphtheritic membrane on the upper portion of the digestive tract.

Pathology

Avian pox occurs in 2 forms, cutaneous (dry) and diphtheritic (wet). The cutaneous form is the most commonly observed and is a self-limiting infection with the lesions regressing and forming scars. Initially, this form of pox appears as a small white, pink or yellow vesicle (blister) on unfeathered parts of the skin (feet, legs, base of the beak, eye margins and head). The vesicle is a result of the separation of the surface layer of the skin with the formation of pockets of watery fluid rich in multiplying virus. The vesicles become nodules as they increase in size, coalesce and burst. Lymph from the cells congeals and scabs are formed. The surface of the nodules become rough and dry and the color changes to dark brown or black. The size and number of nodules present depends on the stage and severity of the infection. Bacteria may gain access causing secondary infection and resulting in a purulent discharge (pus) and necrosis. Eventually, the scab falls off and a scar forms at the site. It takes 2 to 4 weeks for complete healing of the affected areas on the skin providing the lesions aren't too extensive thereby preventing the bird from feeding.

The diphtheritic form involves the mouth, throat, trachea and lungs and consists of yellow or white, moderately raised, moist cheese-like necrotic areas. A diphtheritic membrane forms and may restrict air intake and result in labored breathing and possible suffocation.

Histologically, intracytoplasmic inclusion bodies (Bollinger bodies) are present in the infected skin and respiratory tract mucosa. In the diphtheritic form of the disease, nodular hyperplasia (increase in the number of cells) of the mucosa is observed.

Diagnosis

A presumptive diagnosis of avian pox can be made due to the gross lesions on the body. Confirmation of avian pox is accomplished by microscopic examination for the characteristic Bollinger bodies. Virus isolation by transmission of the organism via egg inoculation, serological results and polymerase chain reaction can also be a means of confirming the disease.

Treatment

There is no known treatment for avian pox in wild birds. In captive situations, there are a variety of treatments that have been used along with supportive care to treat the pox lesions and to prevent secondary infections in various avian species. These treatments consist of removing skin lesions and utilizing sodium bicarbonate or Lugol's solution of iodine washes, removing the diphtheritic membrane from the mouth and throat and swabbing the area with Lugol's solution of iodine, bathing the eyes with a 1-2% saline solution, and raising the environmental temperature. In all cases, providing assistance for recovery may spread the infection to other parts of the skin or to other birds.

Control

The best control for avian pox in captive (turkeys, pheasants, threatened and endangered species) and domestic (chickens and turkeys) birds is vaccination with a modified live vaccine. In wild birds, vaccination is not a feasible method of control.

Avian pox is a highly contagious disease and there are three primary control methods that can be used if infected birds are present. Eliminating standing water will control the primary vector, the mosquito. Infected birds should be isolated or culled to remove the source of the virus. Feeders, waterers, birdbaths and cages should be decontaminated with a 10% bleach solution.

Significance

There is no evidence that the avian pox virus can infect humans and therefore it is not a public health concern.

In some populations of birds (wild turkey, bald eagle and albatross), avian pox may be a significant mortality factor.

September 17, 2010

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.

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 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.

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