Fact Check

Are New 'Super' Lice Spreading Across the U.S.?

The problem of mutated head lice wasn't necessarily a new one.

Published Aug 21, 2015

Image Via Shutterstock
A new strain of treatment-resistant "super lice" is spreading to dozens of states.

In August 2015 (just as kids were heading back to school around the United States), a number of web sites published articles about a purportedly new, treatment-resistant strain of head lice. Among the articles was an 18 August 2015 piece published to TIME, titled "Head Lice in 25 States Are Now Resistant to Treatment." (A regional news site later described it not-at-all terrifyingly as "genetically mutated super lice.")

Given head lice are a massive inconvenience to schools and families without added superpowers, the news spread across Facebook and Twitter quickly. Citing "new research presented at the American Chemical Society’s national meeting," the article reported:

Study author Kyong S. Yoon, PhD, assistant professor in the Biological Sciences and Environmental Sciences Program at Southern Illinois University, has been researching lice since 2000 ... His research is still ongoing, but what he’s found so far in 109 samples from 30 states is startling: the vast majority of lice now carry genes that are super-resistant to the over-the-counter treatment used against them.

In 25 of the states, lice samples had all three of these genetic mutations, making them the most resistant to treatment. Lice populations from four other states had one, two or three mutations, and in just one state -- Michigan -- were the pests not resistant at all to the insecticide.

The articles coincided with an 18 August 2015 press release published by the American Chemical Society. While the release and subsequent reporting were largely congruent, the latter also made it clear that treatment-resistant lice was by no means a new threat. Yoon was described as first having rung the alarm as early as 2000, after separate concerns arose in the 1990s:

Yoon, who is with Southern Illinois University, Edwardsville, explains that the momentum toward widespread pyrethroid-resistant lice has been building for years. The first report on this development came from Israel in the late 1990s. Yoon became one of the first to report the phenomenon in the U.S. in 2000 when he was a graduate student at the University of Massachusetts, Amherst.

In the most recent study, he cast the widest net yet, gathering lice from 30 states with the help of a broad network of public health workers. Population samples with all three genetic mutations associated with kdr came from 25 states, including California, Texas, Florida and Maine. Having all the mutations means these populations are the most resistant to pyrethroids. Samples from four states -- New York, New Jersey, New Mexico and Oregon -- had one, two or three mutations. The only state with a population of lice still largely susceptible to the insecticide was Michigan. Why lice haven't developed resistance there is still under investigation, Yoon says.

So the problem of mutated head lice wasn't necessarily a new one, as the press release clarified, adding: "The solution? Yoon says that lice can still be controlled by using different chemicals, some of which are available only by prescription."

CNN echoed the sentiment:

Reports of lice resistance started appearing in the mid 1990s in the United States, Europe and Australia. A 2014 study suggested the potential for resistance is high in several areas in the United States and Canada. Among lice samples from 84 people in these countries, 99.6% of the insects had mutations in genes that could allow them to survive the insecticides permethrin and pyrethrin, which are the active ingredients in over-the-counter remedies. In the past, this group's research has received financial support from pharmaceutical companies that make such prescription medicine.

The study was presented Tuesday at the American Chemical Society meeting. It has not been evaluated by independent experts for publication in a peer-reviewed scientific journal.

Yoon's research was funded by Sanofi, a pharmaceutical company that owns Sklice lotion, which contains a newer generation lice-fighting chemical.

On 20 August 2015, boston.com published an article titled "‘Mutant’ head lice study funded by companies that treat head lice" which reported:

What sparked the head-lice headline epidemic was a talk by Drs. John Clark of the University of Massachusetts Amherst and Kyong Yoon of Southern University of Illinois at Edwardsville, who came to Boston Tuesday to present their findings on the state of American lice.

They said their study has determined that lice in at least 25 states have developed resistance to over-the-counter treatments and recommended that patients seek out prescription treatments, which can range in cost from $100 to more than $350.

“There is recourse by means of prescription drugs,” Yoon told U.S. News & World Report, another outlet that didn’t note the pharma funding. “Just go to your doctor before you go to your drug store.”

A correction appended to the piece conflicted with CNN's assertion the data had not been peer reviewed: "Correction: An earlier version of this article erroneously stated that the study was not peer-reviewed before it was presented. In fact, it was peer-reviewed and published in the Journal of Medical Entomology."

However, the study linked by the site was dated 14 March 2014, and its findings weren't precisely news. Moreover, the data involved were collected between 1999 and 2009 (years before news articles appeared in 2015 heralding the imminent invasion of super lice).

So while it's true that some research supports the claim lice are growing resistant to common treatment products, researchers first began to observe that trend nearly two decades ago. And although it doesn't necessarily compromise research findings, studies on lice resistant to over-the-counter products have been funded by pharmaceutical companies concurrently marketing prescription-only treatments for head lice.

Kim LaCapria is a former writer for Snopes.