By Susan Milius
Mild winters appear to speed annual menu changes for disease-carrying mosquitoes. And the revised biting patterns might play an overlooked role in worsening the risk of brain infections in people and horses.
The mosquito Culex erraticus spreads the virus that causes eastern equine encephalitis. It’s an uncommon but often lethal disease, killing about half of the people who contract it and virtually all the infected horses. Populations of C. erraticus, like some other mosquitoes, start their biting season targeting mostly birds but end up focusing on deer, horses, people and other mammals.
The timing of when the insects shift from birds to mammals varies a lot from year to year among C. erraticus mosquitoes in Alabama, says entomologist Nathan Burkett-Cadena of the University of South Florida in Tampa. He and his colleagues discovered this variation after eight years of trapping mosquitoes and genetically identifying which bird and mammal species had provided the blood the insects were digesting. In years such as 2007, mosquito populations went mammalian in May or June, but in 2003 waited until August.