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Most Lice Populations Show Resistance to Pyrethroids

104 of 109 samples from 30 states were 100 percent resistant in three point mutations

TUESDAY, Aug. 18, 2015 (HealthDay News) — Most lice populations have point mutations that are linked to pyrethroid resistance, according to a study presented at the annual meeting of the American Chemical Society, held from Aug. 16 to 20 in Boston.

Kyong Yoon, Ph.D., from Southern Illinois University in Edwardsville, and colleagues collected samples from urban and suburban areas in 30 states to examine the distribution of the pyrethroid resistance in a trio of genetic mutations known as knockdown resistance (kdr) in head lice. This genetically-heritable kdr is mainly conferred by three point mutations: M815I, T917I, and L920F.

The researchers found that in numerous states, including Maine, Florida, Texas, Minnesota, and California, 104 of 109 populations were 100 percent resistant in the MI-TI-LF mutations. Intermediate levels of resistance were seen in New Jersey, New Mexico, Oregon, and New York. Michigan was the only state with a largely susceptible population.

“If you use a chemical over and over, these little creatures will eventually develop resistance,” Yoon said in a statement. “So we have to think before we use a treatment. The good news is head lice don’t carry disease. They’re more a nuisance than anything else.”

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