CHAMPAIGN, Ill., 9/7/17: Researchers at the Illinois Natural History Survey (INHS) are surveying and collecting adult female mosquitoes in Illinois and testing how effective insecticides are against them, particularly the Asian tiger mosquito, a species capable of transmitting the Zika virus.
Most adults who become infected with Zika through a mosquito bite experience mild or no symptoms. However, contracting the Zika infection during pregnancy can potentially cause birth defects.
The Asian tiger mosquito (Aedes albopictus) has been found in parts of 41 Illinois counties, most recently in Kane, DeKalb, Douglas, Coles, and Franklin counties. In Champaign County, Aedes albopictus was initially detected in 2011.
“There were very few Asian tiger mosquitoes in Champaign three or four years ago, but now they are quite abundant,” said Chang-Hyun Kim, a medical entomology laboratory specialist in INHS at the University of Illinois. “Of those we tested last year, we didn’t find any mosquitoes carrying Zika, but this species is a vector for the virus.”
Because of this health risk, Kim and Chris Stone, director of the INHS Medical Entomology Lab, are testing local mosquitoes to determine if they are resistant to two common insecticides. The Centers for Disease Control and Prevention recommend that state health agencies explore the possibility of insecticide resistance in case of a Zika outbreak.
“This study aims to determine the effectiveness of insecticides that would be used in an emergency outbreak situation,” Stone said. “Control of the Asian tiger mosquito is already quite difficult—if these populations have developed resistance to certain insecticides, it would be critical to know that.”
To test for insecticide resistance, the researchers coat the inside of glass bottles with insecticide, then place 10 to 20 mosquitoes in each bottle to determine the amount of time and poison needed to kill the insects. Insecticide-resistant mosquitoes will survive for the time and at the dose at which susceptible mosquitoes die, Kim said.
Asian tiger mosquitoes breed in vessels holding standing water—anything from pet dishes and buckets to flower pots and gutters. Female Asian tiger mosquitoes lay eggs just above the water line. The eggs hatch when they are flooded. Once hatched, it usually takes mosquito larvae about 7 to 8 days to become blood-seeking adults.
Applying larvicides to each container would be expensive and time-consuming for municipalities, so health departments rely on residents to control mosquitoes at these sources. Any container that holds water for more than a week should be emptied, Kim said. Bird baths should be cleaned weekly since they are prime areas for mosquito breeding. Mosquito eggs can survive Illinois’ freezing winter temperatures, surviving to hatch in the spring.
This INHS study is funded by the Illinois Department of Public Health and includes updating maps showing the prevalence of Asian tiger mosquitoes in Illinois and focusing on the counties where no mosquitoes of this species have yet been found.
INHS is a division of the Prairie Research Institute, which supports interdisciplinary response teams to address threats to Illinois residents. A response team focusing on the Zika virus has developed updated information on Zika in Illinois, available at http://www.prairie.illinois.edu/responseteams.
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Media contacts: Chang-Hyun Kim, 217-300-4006, maraychk@illinois.edu
Chris Stone, 217-300-5974, cstone@illinois.edu
Tricia Barker, Associate Director for Strategic Communications, 217-300-2327, tlbarker@illinois.edu