A longitudinal study of avian pox in a small passerine, the Dunnock ( Prunella modularis )

Le résumé fourni par la source

Long‐term, longitudinal studies of disease in wild bird populations are rare. Diseases are important determinants of bird survival and may spill‐over into other species including livestock and, in some cases, humans. Avian pox is a globally distributed disease, resulting from infection by viruses in the genus Avipoxvirus (APV). Despite its broad geographical distribution, there are few long‐duration longitudinal studies of its epidemiology, and hence limited understanding of basic processes such as seasonality, and mortality rates of affected birds. Here, we report the results of a 15.5‐year study of a wild population, involving 1549 captures of 588 Dunnocks Prunella modularis , a species recorded as affected by avian pox since the 1940s. Dunnocks were categorized as having avian pox if they were observed with skin lesions suggestive of that disease. The estimated lifetime prevalence of disease was 8.3% (annual range 0–25.8%) at a single site in the UK. No lesions suggestive of avian pox were seen in over 41 000 captures, of over 23 000 individual birds, of 50 other species at the site. No evidence of increased mortality was found in affected Dunnocks: apparent survival probability 0.37 (se 0.12, CI 0.18–0.61, n = 36) for the group with avian pox and 0.32 (se 0.03, CI 0.26–0.38, n = 437) for birds in which it was not detected. Most Dunnocks that developed skin lesions did so in their first calendar year and there was no evidence of disease recurrence, suggesting that a single infection may produce life‐long immunity. In most years, the disease followed a seasonal pattern with a peak in late summer. The same APV DNA sequence was isolated from a skin lesion and from 50% (4/8) of the haematophagous ectoparasitic louse flies taken from apparently healthy Dunnocks at this site, including in years when no cases of avian pox were seen. The results of this study are consistent with APV circulating in Dunnocks with relatively minor adverse effects of avian pox on bird health.

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