CARMEL, Ind., July 28, 2016 /PRNewswire/ -- New evidence has emerged showing that head lice have developed resistance to two types of insecticides that are commonly used in over-the-counter (OTC) treatments for lice infestation, according to a landmark study published in Journal of Medical Entomology (JME)1, as reported by ParaPRO. Findings from the 48-state study showed that, on average, 98 percent of head lice in at least 42 states have developed gene mutations that make them resistant to various pyrethrins and pyrethroids, including permethrin, which is the active ingredient in popular treatment formulations for pediculosis (Nix® (permethrin 1%)). Click here to read the journal article in full.
"This newly published data supports what we've been seeing in our offices and clinics: an increase in treatment-resistant super lice," said Chris Belcher, M.D., Peyton Manning Children's Hospital at St. Vincent, Indianapolis, IN. "It's important that parents contact a clinician if they suspect their child has head lice. There are effective, non-pyrethrin, non-pyrethroid-based prescription agents that can be used if treatment with over-the-counter products such as Nix® has been unsuccessful."
Patient self-diagnosis and misuse of over-the-counter treatment options have contributed significantly to the increase in treatment-resistant head lice. Studies have shown that when self-treating with OTC products, as many as 69 percent of people admit to using more than the recommended dose in an attempt to increase effectiveness. For example, most OTC products recommend two applications for treatment of head lice; however, some data suggest that patients self-treat an average of five times before seeking care from a healthcare provider.2 OTC lice medications are safe when used properly, but misuse could result in side effects such as skin rashes, asthma-like symptoms, and respiratory reactions like rhinitis, swelling of the mouth and larynx, coughing and wheezing.3,4
About the Study
The study, Expansion of the Knockdown Resistance Frequency Map for Human Head Lice (Phthiraptera: Pediculidae) in the United States Using Quantitative Sequencing, was designed to determine the extent and magnitude of the knock-down resistance (kdr)-type mutations responsible for the increasing prevalence of head lice resistant to common treatment formulations. Between July 22, 2013 and May 11, 2015, lice were collected from 138 collection sites in 48 U.S. states and analyzed by quantitative sequencing. Previously published data were used to compare changes in the frequency of the kdr-type mutations over time. The overall mean percent resistance allele frequency (mean % RAF) (+/-SD) for all analyzed lice was 98.3 +/- 10%. Forty-two states (88%) had a mean % RAF of 100%. The frequencies of kdr-type mutations did not differ regardless of the human population size. The study correlated the loss of efficacy of the Nix® formulation (Prestige Brand, Tarrytown, NY) from 1998 to 2013 to the increase in kdr-type mutations. The results demonstrated a parallel increase of kdr-type mutations in lice over time, which provide a plausible reason for the decrease in the effectiveness of permethrin in Nix®.
ParaPRO is a specialty pharmaceutical company committed to partnering with health care providers to address data-driven medical issues involving parasites, including the impact they have on clinical practices and the lives of patients. The company is leading ongoing research into new antiparasitic formulations that address the public health, economic, and personal impacts caused by current treatments for parasite infestation. For more information, visit www.parapro.com.
1.KJ Gellatly, S Krim, DJ Palenchar, K Shepherd, KS Yoon, CJ Rhodes, SH Lee, JM Clark, Journal of Medical Entomology, Expansion of the Knockdown Resistance Frequency Map for Human Head Lice (Phthiraptera: Pediculidae) in the United States Using Quantitative Sequencing, 2016.
2.TL Meinking, L Serrano, B Hard, et al. Archives of Dermatology, Comparative in vitro pediculicidal efficacy of treatments in a resistant head lice population in the United States, 2002;138:220-224.
3.MJ Ellenhorn, Ellenhorn's Medical Toxicology, Williams and Wilkens, Baltimore, MD, 1997.
4.DP West, American Journal of Managed Care, Head Lice Treatment Costs and the Impact on Managed Care, September 1, 2004. Accessed June 2016 at http://www.ajmc.com/journals/supplement/2004/2004-09-vol10-n9suppl/sep04-1894ps277-s282/P-
Nix is a registered trademark of Prestige Brand, Tarrytown, NY.