Scientists have struggled to explain these large outbreaks in the U.S., which stand in stark contrast to the sporadic European infections. In a new study published in the open access journal PLoS Biology, Drs. Marm Kilpatrick, Peter Daszak, and colleagues now present evidence that the major vector of West Nile virus in the USA, Culex pipiens mosquitoes, change their feeding behavior in the fall from their preferred host, American robins, to humans, resulting in large scale outbreaks of disease.
These feeding shifts appear to be a "continent-wide phenomenon," the researchers conclude, and may explain why West Nile virus outbreaks are so intense in the U.S. compared to Europe and Africa, where the virus originates.
From May through September 2005,Dr. Kilpatrick, senior research scientist with the Consortium for Conservation Medicine, and his team collected mosquitoes and caught birds at six sites in Maryland and Washington, D.C. They determined the changes in mosquito populations throughout the West Nile virus transmission season, the abundance and diversity of bird species at these sites, and tested samples for West Nile virus.
Dr. Kilpatrick says, "To find out which species mosquitoes favored as hosts, we collected thousands of Culex pipiens mosquitoes and selected those that had just fed and still had bloodmeals in them. We sequenced the DNA in the bloodmeal to identify the species of host they had fed on."
Their findings showed that from May to June, the American robin, which represented just 4.5% bird po
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Contact: Paul Ocampo
press@plos.org
415-624-1224
Public Library of Science
27-Feb-2006