Insecticide Resistance in Mosquitoes Being Studied


November 19, 2004

Researchers in Texas are studying possible mosquito resistance to the insecticides being used.

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 control the pests. Pyrethroids are chemicals that are linked with endocrine disruption, neurotoxicity, and respiratory irritation. Symptoms of acute toxicity due to inhalation include sneezing, nasal stuffiness, headache, nausea, incoordination, tremors, convulsions, facial flushing and swelling, and burning and itching sensations.

In 2003, the Mosquito Control Division in Harris County sprayed 2 million acres with pyrethroid insecticides in an effort to control disease-bearing mosquitoes, said Ray Parsons, division director. “History has shown that overuse of pesticides will lead to resistance in insects,” said said Dr. Jim Olson, Experiment Station entomologist.

The project was started with a federal U.S. Department of Agriculture Cooperative State Research, Education and Extension Service grant, Olson said. “This is serving as a model for similar problems that could arise anywhere in the state of Texas or the United States,” he said.

“We have to develop new methods of controlling mosquitoes,” Parsons said. “We know we can control them with insecticides, but it’s very expensive and it only works to a certain degree. It’s going to take people going out into the field and learning more about the mosquitoes: the biology of the mosquito and how to control it.” The resistance project is part of a larger program investigating the frequency of mosquito-borne diseases and other possible control methods for mosquitoes, he said.

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