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A new generation of mutant lice, immune to the poisons of decades past, is on the verge of conquering Canadian scalps, says a new report from the University of Massachusetts.

With super lice now constituting 97.1% of Canadian head lice cases, the study, published this month in the Journal of Medical Entomology, warns a new method of killing the mutated parasites is “critically needed.”

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The super lice have a “TI mutation,” a gene that makes them resistant to pyrethrins and pyrethroids, the cheap and safe insecticides that constitute the key ingredients in most anti-lice shampoos, creams and sprays.

In the United States, more than 3,500 consumer products use one of these two insecticides. In Canada, they dominate the market for over-the-counter delousing products.

But while these chemicals were once a miracle lice-killing cure, only 2.9% of Canadian head lice cases can now expect to use these products with any success.