In over 25 states in the United, head lice have shown resistance to ordinary medicines.
When its time to go back to school, there are so many challenges. And head lice are just one of them. The itchy scalps lead to many days of missed classes. Lice show resistance to common treatments. That is in over 25 states of the US of A.
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These OTC drugs are still prescribed by scientists. And they have no effect on head lice. The researchers presented their work at the 250th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society.
"We are the first group to collect lice samples from a large number of populations across the U.S.," says Kyong Yoon, Ph.D. "What we found was that 104 out of the 109 lice populations we tested had high levels of gene mutations, which have been linked to resistance to pyrethroids."
Lice samples got collected from a variegated population. The lice all showed genetic mutations. These anomalies cause resistance to pyrethroids.
Pyrethroids are a class of insecticides. They're used to kill mosquitoes and other insects. They have within them permethrin, which gets used to kill lice.
The pyrethroid-resistant lice populations have been building up for quite some time. The information regarding this was common knowledge in the 90s in Israel. The fact became well-known in the United States in the year 2000.
Yoon became one of the first to report the phenomenon in the U.S. in 2000. He was a graduate student at the University of Massachusetts, Amherst.
"I was working on insecticide metabolism in a potato beetle when my mentor, John Clark, suggested I look into the resurgence of head lice," he says. "I asked him in what country and was surprised when he said the U.S."
Lice populations in the states in pink have developed a high level of resistance to some of the most common treatments. // Credit: Kyong Yoon, Ph.D.
The lice got tested for kdr (knock-down resistance). All the lice showed remarkable kdr mutations. Most of these kdr mutations had begun with houseflies in the 70s. But now they had spread to the lice population as well.
Kdr mutations changed the nervous systems of lice. They made them highly resistant to pyrethroids. A large number of states had lice samples collected from within their environs. The result was that those lice with kdr mutations comprised 25 states as their provenance.
The states included within their purview: Florida, Maine, Texas and California. These had lice with the most mutations. States such as New York, New Jersey, New Mexcio and Oregon had fewer mutations in the lice that existed in their loci. In fact, the only state that had lice that got affected by insecticide was Michigan.
Many insects develop immunity to pesticides and insecticides. This happens in case of termites, ants and cockroaches. Over time the insects begin to become resistant. That is to the dire consequences of the insect killing drugs.
They have less and less of an effect on the insect. Finally, the subsequent generations of the insect population become used to the insecticide. It cannot harm them at all. This is similar to the manner in which several antibiotics end up not wiping out the harmful bacteria.
That is due to immune resistance which gets built up over a period of time. Ultimately, other methods will have to be found. That is to conquer the harmful insect populations of the world. After all, they outweigh all the other species put together.
"If you use a chemical over and over, these little creatures will eventually develop resistance," Yoon says. "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."