Texas Agricultural Experiment Station, Texas Cooperative Extension and the Mosquito Control Division of the Harris County Public Health and Environmental Services Department are working together to study insecticide resistance in mosquitoes and develop a strategy to overcome it.

Larvae of Culex quinquefasciatus, or the southern house mosquito, are being collected in the Houston area and raised in laboratories at Texas A&M University. Adult mosquitoes are then tested to see whether genetic mutations have made them resistant to the pyrethroid pesticides used in the district, said Dr. Patricia Pietrantonio, Experiment Station entomologist.

The southern house mosquito is the primary vector for viruses causing St. Louis encephalitis and West Nile encephalitis in Texas urban areas.

"For diseases like St. Louis encephalitis and West Nile encephalitis, the only control is mosquito control," said Dr. Jim Olson, Experiment Station entomologist. "There are no vaccines. You can only treat the symptoms in the hospital."

These two diseases may be fatal to humans, with West Nile being fatal to other mammals as well as birds.

Fragments of mosquito genes will be cloned and sequenced to determine what mutations, if any, have occurred, Pietrantonio said.

"If mutations have taken place," she said, "the insect will no longer die" when treated with insecticides.

The project is similar to one she completed in the Houston area in 1998 involving the organophosphate insecticide, Malathion. Pietrantonio found in some areas the southern house mosquito was resistant to the insecticide Malathion being used. The district switched to pyrethroid pesticides to contro
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Contact: Edith Chenault
e-chenault1@tamu.edu
979-845-2886
Texas A&M University - Agricultural Communications
10-Nov-2004