West Nile virus from an avian conservation perspective

Abstract

West Nile virus (WNV) is a widespread and ecologically adaptable virus for which birds are major amplifying hosts. Its unexpected arrival to North America in 1999 gained worldwide attention, in part because of the resulting mortality in birds. The virus is now endemic in North America, and sporadic outbreaks continue in Africa, the Middle East, as well as Europe and Russia. Avian taxa vary in their susceptibility to WNV-associated disease, with North American corvids being the most severely affected. Recent North American and European WNV strains have experimentally induced morbidity and mortality in birds; however, avian deaths have not been a prominent feature of WNV epidemiology outside of the United States and Canada. Bird species experiencing population declines include the Yellow-billed magpie Pica nuttalli, American crow Corvus brachyrhynchos and Blue jay Cyanocitta cristata. The American robin Turdus migratorius is noteworthy for its important role in transmission. Methods to reduce WNV transmission range from screened enclosures to aerial pesticide spraying. In addition, numerous vaccines have been administered to birds with unreliable but occasionally encouraging results. Avian conservation efforts will continue to be challenged with controlling WNV spread and transmission owing to the wide geographic range of the virus, diversity and abundance of mosquito vectors and global climatic trends.