Avian Pox

Causative Agent

A disease of the skin of birds caused by infection with the Avipoxvirus group of viruses.

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Avian pox lesions are typically found on the featherless regions of the body. As the disease progresses, pox lesions become more extensive potentially impairing sight, breathing and feeding, such as in this immature bald eagle.

Suspected avian pox in a young of the year bald eagle. A nostril has been completely occluded with a pox-like lesion. The legs and feet of the same eagle show lesions characteristic of avian pox.

Distribution

Geographic:

Avian pox has been reported worldwide.
Avian pox is viewed as an endemic disease in birds. Because of increased frequency of reported cases involving new species it is also viewed as an emerging disease.
Mosquitoes and birds acting as carriers can spread the disease at bird feeders and through migratory flyways.

Seasonality:

Infection with avian pox can occur throughout the year.
Environmental factors, the activity of mosquitoes, and the habits of the species affected by avian pox can regulate when outbreaks occur.

Hosts, Transmission and Life Cycle

Hosts:

Approximately 60 free-living bird species have been reported with avian pox.
Most commonly reported in songbirds, upland game birds, marine birds and birds of prey.

Transmission and Life Cycle:

The virus stimulates the upper layers of the skin to grow rapidly; this new tissue soon dies.
Avian pox can be acquired either through:
- transfer from infected hosts via infected mouth parts of mosquitoes
- direct contact with surfaces or air-borne particles contaminated with poxvirus can result in infections when the virus enters through abraded skin or though mucous membranes
Avian pox virus can survive considerable dryness; therefore, dust particles containing the virus can remain infective for extended periods.

Signs and Symptoms

Two forms: “cutaneous” (involving the skin) and “wet” (involving internal organs).
Cutaneous form is more commonly reported in wild birds:
- birds with wart-like nodules on the featherless areas of the body, including the feet and legs, margins of the eyes, and base of the beak should be considered suspect cases of avian pox
- birds may appear weak and emaciated if the nodules have interfered with feeding
- laboured breathing may be observed in birds where air passages have been blocked
- birds may fully recover provided they are able to feed. The disease usually is self-limiting and leaves only minor scars
- growths can grow and form clusters which may impair sight, breathing and feeding
- secondary bacterial and fungal infections of pox lesions are common with cutaneous forms of avian pox infection
Wet avian pox is commonly reported in domestic chickens and turkeys and less commonly in wild birds, likely because it is less visible than the cutaneous form:
- wet pox involves lesions of the mucous membranes of the mouth and upper digestive and respiratory tracts
- wet pox may contribute to mortality and sickness leading to the removal of infected birds by predators and scavengers

Meat Edible?

Meat from an infected animal is suitable for human consumption, however, trim off affected parts and do not consume the lungs or associated tissues.

Human Health Concerns and Risk Reduction

There is no evidence that avian pox virus can infect humans.
If birds with suspected avian pox are handled and other live birds are to be handled in the future, any surface that infected birds have come in contact with should be cleaned with a 10% household bleach solution to prevent the spread of the disease to other birds.

Samples for Diagnosis

A tentative diagnosis of avian pox can be made based on the appearance of wart-like lesions on the body; however, this must be confirmed with microscopic examination and virus isolation.
Submission of the whole bird or affected body parts are needed for virus isolation.
Specimens should be frozen if held more than a day before shipment to the diagnostic laboratory.