As if battling head lice isn’t bad enough, newly published research says killing the dreaded bugs has become harder than ever. 

Researchers in the U.S. are warning people about the prevalence of head lice that are resistant to insecticides found in most commonly used anti-lice shampoos and ointments.

This “super lice” variation is now present in 97.1 per cent of Canadian and 99.6 per cent of U.S. lice cases, according to a study published this month in the Journal of Medical Entomology.

The so-called “TI mutation” is making lice immune to pyrethrins and pyrethroids, insecticides that have been safely used for decades to kill off the critters, researchers said.

Based on a DNA analysis of lice samples from 32 locations in Canada and the U.S., researchers concluded that the prevalence of the TI mutation is “uniformly high” across North America.

“Alternative approaches to treatment of head lice infestations are critically needed,” they wrote.

The Canadian lice samples were collected in 2008 from more than a dozen communities in three provinces: Quebec, Ontario and British Columbia. The only cities where lice susceptible to pyrethrins and pyrethroids could still be found were Toronto, Oakville, Ont., and Sudbury, Ont.

This is not the first time researchers have noted the alarming percentage of treatment-resistant lice. A Canadian study published in 2010 also found that 97.1 per cent of tested lice were resistant to pyrethrins or pyrethroids.

Jason Tetro, a microbiologist who was not involved in the study, said the lice mutation likely started happening decades ago, as the use of insecticides expanded.

Just like some bacteria develop a resistance to antibiotics from overuse, lice have built up tolerance to widely used insecticides, Tetro told CTV News Channel Friday.

“Over the last 60 years, it’s gone worldwide,” he said.

Not all hope is lost, however. The latest study notes that clinical tests have shown the effectiveness of other substances, including benzyl alcohol, spinosad (an insecticide) and ivermectin (anti-parasitic medicine), in the battle against lice.

Some people also swear by natural treatments, such as coconut or tea tree oil, vinegar, and even mayonnaise.

And while adult lice may be difficult to get rid of, another study recently published in the Journal of Medical Entomology found that removing lice eggs with plain old conditioner and water is just as effective as using more expensive nit removal products.