Poxvirus Infection in Birds

Poxviruses can infect many species of birds, and each species may have its own unique species of poxvirus (e.g., mynah bird pox, canary pox, psittacine pox, fowl pox, falcon pox, pigeon pox). There are 10 distinct strains of poxvirus, affecting over 239 species of birds. Poxviruses can cause various clinical signs, depending on 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 (skin) form, diphtheritic (respiratory) form, and the septicemic form. 

• In the cutaneous (skin) form (dry pox), 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 (wet pox), thickened plaques occur in the mouth, throat, or sinuses. These lesions may occur by themselves or with skin lesions. 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 septicemic form occurs when the virus gains entry into the bloodstream, and it can affect a variety of internal organs, including the heart, lungs, and liver. This form usually presents as a severely depressed bird that 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 are sent to a pathologist for identification of the poxvirus. An issue of concern is that cutting into or damaging a poxvirus lesion may cause the virus to spread to adjoining tissues. Most avian veterinarians can get a good presumptive diagnosis by looking at the affected tissues, especially in the cutaneous form. While the skin lesions and plaques that occur in poxvirus infection can suggest poxvirus, other diseases may look similar and should be ruled out, such as abscesses, tumors, and bacterial or fungal diseases.

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 affected by the cutaneous form will recover with supportive treatment. Topical treatment of the crusts may be required. Care must be used not to disturb or remove any crusts, as this may cause the virus to spread locally. Antibacterial therapy is often used if a secondary bacterial infection is present. Prevention is key in this disease. Chickens and pigeons may be vaccinated against poxvirus. The use of mosquito netting around outdoor cages and flights will help prevent biting insects in regions where the virus is endemic. 

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. Contact an avian veterinarian if you notice crusty swellings on the face or feet of your bird(s).