Think you’re a mosquito magnet? At least you’re not a robin. Two independent studies suggest the American robin may be a prime source of blood for Culex mosquitoes in Northeast and Mid-Atlantic states and as such, the single biggest summer reservoir of the West Nile virus.‘‘What happens with American robins is not only do mosquitoes prefer to feed on them, but they produce a lot of viral particles and survive the infection,’’ said Peter Daszak, co-author of one of the studies and executive director of the Manhattan-based Consortium for Conservation Medicine. ‘‘American robins are much more responsible for propagating the virus and infecting mosquitoes than other birds such as crows or house sparrows.’’ Although primarily transmitted between birds and mosquitoes, the West Nile virus can readily infect humans, horses, and other mammals. Since its North American debut in 1999, the virus has claimed more than 800 human lives, while sickening an estimated 225,000 people. Most human cases, though, have been relatively mild. Recent studies on the feeding behaviour of West Nile-carrying female mosquitoes have used DNA sequencing to identify the blood of victims ranging from skunks and dogs to humans and a menagerie of birds. In March, researchers from the Connecticut Agricultural Experiment Station in New Haven reported in the journal Emerging Infectious Diseases that American robin blood accounted for more than one-third of the meals in Culex pipiens and Culex restuans mosquitoes, the two species most strongly implicated in West Nile virus transmission in the Northeast. A more recent study by Daszak and his collaborators in an online edition of the Proceedings of the Royal Society B found that robins accounted for an even larger percentage—43 percent—of Culex mosquito blood meals at five sites in Washington, D.C., and Maryland. Those feedings were nearly 17 times more abundant, on average, than would be expected if the mosquitoes had shown no feeding preferences.Researchers cannot yet explain the source of the attraction, whether based on the robin’s colour, a chemical signal or a more exposed night roost. But in a separate study, Daszak and his colleagues suggest the migration of robins in late August and September may shift the focus of Culex mosquitoes onto humans, with a subsequent spike in human West Nile infections. ‘‘When the robins move away in later summer, suddenly these mosquitoes are looking around for something else to feed on,’’ he said, ‘‘and unfortunately they pick on us.’’ (Bryn Nelson)
