Prevalence of neutralizing antibody and virus shedding in psittacine birds infected with avian polyomavirus
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Infection with avian polyomavirus is common in captive psittacine birds. While polyomavirus is rarely pathogenic in adult birds, infection of susceptible nestlings may result in a fatal disease. In this study, the prevalence of parrots with inapparent infection was investigated in four aviaries by two techniques: a specific polymerase chain reaction assay to detect viral DNA in cloacal swab and fecal samples, and a virus-neutralization assay to detect viral-specific antibodies in serum. The prevalence of infection, as determined by the results of these assays, was species, age, and aviary dependent. A high prevalence of infection was found in cockatiels (Nymphicus hollandicus) (86.5%) and mature parrots (71.5%), while only 10% of budgerigars (Melopsittacus undulatus) had evidence of viral exposure. However, most budgerigars in this study were of the English variety, suggesting that English budgerigars may be naturally resistant to infection with avian polyomavirus. In contrast, a high frequency of shedding was found in cockatiels, which suggests that they may be an important source of virus dissemination. A small subset (17.4%) of adult parrots that were infected with avian polyomavirus also shed virus one or more times. Assays of three cloacal swab samples obtained 6 months apart were necessary to detect all of the virus-shedding birds. Viral-neutralizing antibody titers could not be used to predict which birds would shed virus. During the study period, the antibody titers of all of the cockatiels and 25% of the adult parrots declined to undetectable concentrations. 1997 by the Association of Avian Veterinarians.