As children head back to school this fall, healthcare professionals should be on alert for cases of "super lice." Although lice measure only 2.1 and 3.3 millimeters, today's strains are resisting traditional over-the-counter treatments, making them seem larger than life.
The best defense against an infestation is to know the signs and treatment options. An itchy scalp is an obvious symptom, but an infestation doesn't cause this symptom in everyone.
"Only 50% of people itch from it because it is an allergic reaction to the bug bites," explained Michele Barrack, founder of Lice Lifters lice treatment clinics. "We recommend weekly head checks with a good lice comb on wet hair-it is the only good way to see it.
Lice Lifters, which has 13 locations in four states, has seen a marked increase in business since news of the resistant strain broke in spring 2016. She said Lice Lifters has successfully treated many cases. These and other treatment facilities suffocate lice using various methods. They also offer alternatives to over-the-counter lice shampoos that use chemicals such as permethrin and pyrethrin.
Lice have been building up immunity to anti-parasite treatments since the 1990s, when resistance was first reported in Israel, according to findings presented at the 250th National Meeting & Exposition of the American Chemical Society in August 2015.1
"Permethrin has been the mainstay treatment for head lice for over a decade, as a result of other, potentially more dangerous, treatments being removed from the market," explained Ray Tsai, MD, president and chief medical officer of Children's Health Pediatric Group based in Dallas. "As a result, an arms race has developed, and some lice have developed mutations that protect them from permethrin."
The use of permethrin has been scrutinized for a suggested link to cancer. The Environmental Protection Agency determined that permethrin was "likely to be carcinogenic to humans" if it was eaten, based on lab tests that caused tumors in mice and rats in the early 1990s.2 However, the International Agency for Research on Cancer could not determine whether or not permethrin would cause cancer when used topically. Still, some advocates worry that cancer risk could increase in patients with open wounds on the scalp (commonly resulting from scratching at the lice). Shampoos and treatments containing permethrin are commonly used despite these questions.
Prescription medications recommended for head lice include benzyl alcohol 5% (Ulesfia), which is applied to the hair, left on for 10 minutes, and then rinsed off. Malathion lotion (Ovide) is applied to hair on the head, left on for 8 to 12 hours, and then rinsed off. If lice are still present 7 to 9 days later, a second treatment is necessary.
The latest U.S. studies looked at samples from 30 states and found a trio of genetic mutations known collectively as "knock-down resistance," or KDR, in 25 of them. Since the findings suggest that OTC lice preparations contribute to desensitization, preventing re-infestation is just as important as getting rid of the lice.
"Don't forget that killing the lice is not the larger problem: removing all of the eggs or nits is the tricky part of getting rid of lice," Barrack warned. "If you miss two or more eggs (they are glued to the hair), they will hatch and you will have lice all over again."
The Centers for Disease Control and Prevention advises against treating an infested person more than 2 to 3 times with the same medication if it does not seem to be working. If resistance is the reason, healthcare providers can prescribe an alternative agent or may advise the patient to visit a lice removal service.3
To make sure no louse is left behind, anything worn or used by the infested person in the 2-day period before treatment-such as pillow cases, bedding, clothing and towels-should be machine washed and dried. Using the hot water and hot air cycles will kill lice and nits. This occurs after a 5-minute exposure to temperatures greater than 128.3° F, the CDC reports.3 Items like headbands or baseball hats that can't be machine washed should be sealed in a plastic bag for 2 weeks. Lice cannot survive for more 24 hours without a host. However, the CDC recommends that such items remain outside until the household is deemed lice-free.
An estimated 6 million to 12 million children between ages 3 and 12 will get head lice this year. To minimize the risk, children should avoid sharing personal belongings such as hairbrushes, hair accessories, scarves or headphones with friends or classmates. Kids and parents should also be aware of shared spaces like school coatrooms, where lice may have the chance to crawl from one jacket hood to the other.
A final note is that lice are known to be more active at night. So, it's not just an annoying coincidence if a patient reports increased itching right before bedtime. It's best to do a quick check before the entire family is exposed via the next hug or selfie.
Chelsea Lacey-Mabe is a freelance writer in the Philadelphia area.
1. Time Magazine. Lice in 25 states show resistance to common treatments. http://time.com/4000857/lice-treatment/
2. National Pesticide Information Center. Permethrin Fact Sheet. http://npic.orst.edu/factsheets/PermGen.html
3. Centers for Disease Control and Prevention. http://www.cdc.gov/parasites/lice/head/treatment.html