Avian pox is a slowly developing disease of birds caused by several different strains
of avipoxvirus. A variety of birds worldwide, including upland gamebirds, songbirds,
marine birds, and the parrot family can become infected.
Raptors are occasionally affected, but the disease is rare in waterfowl.
Transmission occurs via direct contact with infected birds, ingestion of food and water contaminated by sick birds
or carcasses, or contact with contaminated surfaces such as bird feeders
and perches. The virus enters through abraded skin. Insects, especially
mosquitoes, act as mechanical vectors.
Avian pox can occur
in two forms: cutaneous pox and diphtheritic or "wet" pox. In cutaneous
pox (the most common form), wartlike growths occur around the eyes, beak
or any unfeathered skin. This leads to difficulty seeing, breathing, feeding,
or perching. In diphtheritic pox, the growths form in the mouth, throat,
trachea and lungs resulting in difficulty breathing or swallowing. Birds
with either form of pox may appear weak and emaciated.
The cutaneous form of pox causes warty growths on unfeathered skin,
sometimes in large clusters. The size and
number of growths depend on the stage and severity of infection. Common
sites include feet, legs, base of beak, and eye margins. Birds are often emaciated
due to inability to feed. In the diphtheritic form, there are raised,
yellow plaques on the mucus membranes of the mouth and throat.
The disease can be
a significant mortality factor in some upland game bird populations during
fall and winter months, in songbirds over winter, and in
raptor populations. Birds can survive with supportive
care, food and water, and protection from secondary infections. Warty
scabs contain infectious viral material. Disease control recommendations
are site specific, therefore contact the National Wildlife Health Center
for assistance. Decontamination of bird feeders, birdbaths, transport
cages and banding equipment with 10% bleach and water solution is recommended.
In some situations, removing infected birds can be important to reduce
the amount of virus available to vectors and noninfected bird populations.
Vector control may be considered in affected areas.
For more information
on Avian Pox, please contact: The USGS National Wildlife Health Center, at 608-270-2400.
Photo by Wallace R Hansen
Public Health Significance
There is no evidence of human risk from avipoxviruses.
Domestic Animal Significance
Poultry are susceptible and many are vaccinated against pox. The safety and effectiveness of this
vaccine in wild birds is not currently known.