Cooler Temperatures Make Mosquitoes More Dangerous
June 4, 2013

Cooler Temperatures Make Mosquitoes More Dangerous

Lee Rannals for — Your Universe Online

Researchers wrote in the journal PLoS Neglected Tropical Diseases that weather could be influencing the transmission of the West Nile virus and other mosquito-related disease.

The scientists said mosquitoes living in cooler temperatures have weaker immune systems, making them more susceptible to dangerous viruses and more likely to transmit them to people. They said this connection is significant in light of global climate change.

"Our data offers a plausible hypothesis for how changes in weather influence the transmission of these diseases and will likely continue to do so in the future," said Kevin Myles, associate professor of entomology in the College of Agriculture and Life Sciences (CALS) at Virginia Tech.

The team's work suggest that it would be unwise to focus solely on warmer temperatures when considering links between climate change and disease transmission.

"Mosquitoes like to breed and lay their eggs in dark, cool places because that means the water will last longer," said Zach Adelman, associate professor of entomology at CALS. "They don't lay their eggs in sunny spots because that will dry the water out in a day or two. Although this has been known of some time, we are just learning about its potential effects on the mosquito immune response. Hopefully, this information can be used to build better models that more correctly predict when we'll have disease transmission."

Current computer modeling of outbreaks considers meteorological variables and human population indexes but has failed to consider the effect of temperature on mosquito immunity. The team found that the mosquito's RNA interference pathway is impaired when reared at cooler temperatures.

The rate of transmission of both diseases has increased with outbreaks occurring in unexpected places, like introductions of West Nile virus to New York in 1999 and the chikungunya virus to Italy and France in 2007 and 2010.

Last April, the California State Legislature declared the week of April 21 through 27 2013 as West Nile Virus and Mosquito and Vector Control Awareness Week in California. West Nile virus is a disease transmitted by mosquitoes that can result in debilitating cases of meningitis and encephalitis, and leads to death in humans, horses, some bird species and other wildlife.

According to the California Department of Public Health (CDPH), 479 human cases of West Nile virus were reported in 2012, and of those, 19 fatalities were reported.