Poxviruses can infect many species of birds, and each species of bird may have its own unique species of poxvirus (mynah bird pox, canary pox, psittacine pox, fowl pox, falcon pox, pigeon pox, etc.). There are 10 distinct strains of the poxvirus, affecting over 239 species of birds. Poxviruses can cause several different clinical signs, depending upon which part of the body is infected.
What are the clinical signs of poxvirus infection?
There are several distinct clinical syndromes seen in birds infected with a poxvirus; cutaneous or dry pox, diphtheroid or wet pox, and the septicaemic form.
In the cutaneous (skin) form of the disease, nodular, raised, or crusted areas of the non-feathered skin are seen. This form is common in pigeons, chickens, and canaries. These lesions usually occur around the face and on the feet, beginning as white or yellow areas that rapidly progress to form crusts or, in advanced cases, bloody scabs. In lovebirds, poxvirus lesions often appear on darkened or discolored areas of the skin. In the diphtheritic (respiratory) form of poxvirus infection, thickened plaques occur in the mouth, throat, or sinuses. These lesions may occur by themselves or with skin lesions.
"The diphtheroid form causes severe plaque formations on the oral cavity, trachea, esophagus, or crop."
The diphtheroid form causes severe plaque formations on the oral cavity, trachea, esophagus, or crop. Secondary bacterial and fungal organisms invade the lesions and cause a dramatic worsening of respiratory or digestive disease. This form is more common in psittacines (parrots), pigeons, pheasants, and chickens.
The septicaemic form occurs when the virus gains entrance into the bloodstream and can affect a variety of internal organs including the heart, lungs, and/or liver. This form usually presents as a severely depressed bird that usually dies shortly after showing symptoms. Canaries are affected the most by this form.
How is poxvirus diagnosed?
The most accurate diagnosis is made by a biopsy of the lesion. Biopsy specimens will be sent to a pathologist for identification of the poxvirus in the tissues submitted. Most accomplished avian veterinarians can get a very good presumptive diagnosis from the visual presentation of the tissues affected, especially in the cutaneous form. An issue of concern is that cutting into or damaging a poxvirus lesion may cause the virus to spread to adjoining tissues.
"...cutting into or damaging a poxvirus lesion may cause the virus to spread to adjoining tissues."
While the skin lesions and plaques that occur in poxvirus infection can be very suggestive, other diseases such as abscesses, tumors, and bacterial or fungal diseases may look similar and should be ruled out.
How is poxvirus transmitted?
Most often, mechanical vectors, such as mosquitoes and biting flies, transmit the virus from an infected bird to a non-infected bird; birds that are housed outdoors are more susceptible than those kept indoors. However, mosquitoes and flies can also come indoors. The virus can also be transmitted by ingestion of infected scabs or inhalation of aerosols. The incubation period is generally 5-10 days after exposure.
Flock outbreaks may last for months. The virus is difficult to eliminate and it is long-lasting in the environment.
How is poxvirus treated?
"Many birds will recover with supportive treatment."
Many birds will recover with supportive treatment. Topical treatment of the crusts may be indicated. Care must be used not to disturb any crusts, as this may cause the virus to spread locally. Antibacterial therapy is often used if a secondary bacterial infection is present.
How can I minimize the risk of infection for my bird?
The best control is prevention. Healthy birds can be vaccinated, although it is usually done for birds living in a flock rather than an isolated household pet. Control of mosquitoes and flies is critical if birds are housed outdoors. Raise your birds indoors and use insect-proof screening.