Poultry, Fisheries & Wildlife Sciences
Open Access

Avian Polyomavirus

Malawo Memba^{* *}Correspondence: Malawo Memba, Department of Zoology, Pukyong National University, Busan City, Republic of Korea, Email:

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About the Study

Avian polyomavirus (APV) primarily affects young birds. There are two primary forms of the disease based on species affected: budgerigar fledgling disease and a nonbudgerigar polyoma infection. Both are characterized by peracute to acute death of preweaned neonates. Adult birds typically are resistant to infection; they will seroconvert and shed the virus for up to 90 days, then clear the infection. The incubation period is 7-10 days.

The typical presentation of budgerigar fledging disease is a well-fleshed juvenile, just before fledgling age, with acute onset of lethargy, crop stasis, and death within 24–48 hr. Other clinical signs are cutaneous hemorrhage, abdominal distention, and feather abnormalities. Surviving budgerigars >3 wk old often exhibit feather dystrophy (French molt or feather dusters). In other species of psittacines <4 month old, the infection is also often fatal. Older non budgerigar psittacines may have subclinical disease or hemorrhages and coagulopathies. Prevalence of the virus in adult psittacines, including budgerigars, is thought to be high.

Antemortem diagnosis is accomplished with DNA probes of cloacal swab and blood samples and virus-neutralizing antibody tests of blood samples to identify birds with previous viral exposure. Diagnosis in a flock setting is typically based on clinical signs, signalment, and necropsy findings.

Gross necropsy findings in deceased chicks often include pale skeletal musculature and subcutaneous ecchymotic hemorrhages. The kidneys and liver are enlarged and may be pale, congested, and mottled, or have pinpoint, white foci. Petechial or ecchymotic hemorrhages may also be present on viscera, particularly the heart. The heart is sometimes enlarged and may show hydropericardium. Intranuclear inclusion bodies are often seen in the liver, kidneys, heart, spleen, bone marrow, uropygial gland, skin, feather follicles, etc.

Aviary control methods include avoiding the housing of budgerigars or lovebirds on premises where other species are bred, adhering to standard hygiene procedures, preventing access to the nursery by visitors, and not introducing birds into the aviary without 90 days quarantine and testing. Eliminating APV infection from an infected budgerigar aviary is challenging. First, all breeding must be stopped for 6 months. The presence of infected neonates, fledglings, and adults propagates the disease. During this time, adult birds are moved to a noninfected area while the entire aviary is disinfected. Nest boxes should be disinfected or discarded and replaced. After 6 months, adult breeding birds can be returned to a clean aviary and breeding resumed.

Prevention

Pet store prevention should include separating neonates from different sources, purchasing birds from sources where polyomavirus testing and vaccination are performed, and ideally, not purchasing or selling unweaned birds.

Treatment

Treatment is supportive care. A vaccine is available. For breeding birds, two doses of the vaccine are administered at a 2-wk interval; this should be done off-season. The manufacturer recommends administration of the first dose when the chick is >35 days old, with a booster vaccination in 2-3 wk.