A growing resistance to over-the-counter and prescription drug treatments developing in head lice has led doctors and scientists in pursuit of an end-all solution to this perennial childhood affliction.
Researchers at the University of Massachusetts have now discovered that ivermectin - a compound used to treat intestinal worms and parasites - may hold the key to stopping head lice.
Head lice are resisting currently used treatments because medications are "using compounds that all act on the same part of the louse's nervous system," said John Marshall Clark, a UMass professor of Veterinary and Animal Sciences.
Ivermectin proved 100 percent effective at killing head lice in a recent study conducted by Clark.
Clark and his team of researchers tested ivermectin on a strain of lice collected from school children in Florida. The particular strain that they used showed resistance to permethrin, the insecticide used as the active ingredient in many over-the-counter treatments.
Compounding the problem of lice becoming resistant to current treatments, many of those same treatments pose a danger risk if not used properly.
"Since most people find head lice intolerable, they often repeatedly apply insecticides without realizing their potential harm if overused or misapplied," Clark said in a statement.
According to Clark, these insecticides would have to be overused on a grand scale to be harmful because they have a chronic, rather than acute toxicity. This means that the harmful effects only occur following a long build up of exposure to the toxin, rather than immediately after any exposure to the toxin.
Using ivermectin in treatments may bypass both of these problems associated with current treatments.
In Clark's study, ivermectin was mixed with water, olive oil, shea butter and other ingredients in order to put the treatment into a form that can be applied to the skin or scalp. The product was 100 percent effective in killing the lice after just 10 minutes. The topical mixture of ingredients even made the product more effective, which might indicate that it allowed the ivermectin to penetrate the lice more easily.
The advantage of ivermectin is that its rapid effectiveness would keep people from overusing it, and it is not well-absorbed through the skin. This makes it less harmful in externally used products
The potential harm of chronic exposure to toxins, according to Clark, is shown in lice-killing pesticides such as malathion. This pesticide is used in the treatment Ovoide, and contains organophosphates, "which when overused produces organophosphate induced delayed neuropathy (OPEDN). This is when cells in the nervous system start degrading," said Clark.
Head lice affects 12 million people in the U.S. per year, mainly children. Unfortunately, children are also more susceptible to the harmful products in treatments.
"Children are usually more susceptible to toxins because they don't metabolize them as quickly. Also, they are still developing so their nervous systems are going through change," said Clark.
Caitlin Quinn can be reached at cquinn@student.umass.edu.
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