More stress for birds means higher chances of West Nile virus
September 6, 2016| Dana Kobilinsky | THE WILDLIFE SOCIETY
Researchers examined the extent to which mosquitoes with West Nile virus bit zebra finches with elevated levels of stress.
Birds that have more of the stress hormone corticosterone are more likely to be bitten by mosquitoes that can carry West Nile virus, according to a new study.
“This particular study is the first chain linking the interaction between the virus, the mosquito and the bird,” said senior author of the study, Lynn (Marty) Martin, who is an associate professor at the University of South Florida.
Martin says it’s important to think of the disease as a process, with the first step being the virus finding its hosts, which, in this case, are birds. “We were looking at how stress hormones affect the contact rate of mosquitoes with birds,” he said. “Lo and behold, we found that stress hormones were pretty important in mosquitoes choosing which hosts to bite.”
They found that the birds with the stress hormones were more defensive although it isn’t clear why that didn’t keep them from getting bitten. Martin speculates the stressed birds may have been so attractive to the mosquitoes that they were determined to keep trying to bite until they succeeded.
Martin says this research has implications for management of wildlife, particularly species that are infected by West Nile virus. Elevated levels of the hormone for a long period of time are responsible for these increases in mosquito bites, he says. These elevated levels may occur as a result of habitat manipulation, noise pollution, light pollution and other anthropogenic stressors in the wild.
Martin says this study is part of larger effort to understand how stress hormones affect West Nile in wildlife. “We’re trying to get the last couple of experiments done to discover all of the stages at which stress hormones might affect West Nile dynamics,” he said. “We want to know how stress affects the way birds deal with the virus, but we especially want to know how stress affects the transmission of virus from infected bird back into mosquitoes.”