Treatment-resistant lice with one or more genetic mutations have been identified in at least 25 states, according to research presented at the 250th National Meeting & Exposition of the American Chemical Society (ACS).

Kyong Yoon, PhD, from Southern Illinois University in Edwardsville, IL, collected population samples from 30 states to investigate three specific genetic mutations in lice. The genetic mutations called kdr (“knock-down resistance”) had initially been identified in house flies in the late 1970’s after farmers began to use pyrethroids from DDT and other harsh insecticides.

Of the 109 lice populations tested, 104 had high levels of the gene mutations. Population samples with all three genetic mutations were identified from 25 states, including California, Florida, Maine, and Texas. Samples from New Mexico, New Jersey, New York, and Oregon had one, two, or three mutations; the only state without any mutations was Michigan, although researchers are not sure why.

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Lice can be successfully treated with products containing other chemicals, some of which require a prescription. Dr. Yoon added that “if you use a chemical over and over, these little creatures will eventually develop resistance. So we have to think before we use a treatment.”

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Areas with identified treatment-resistant lice highlighted in red