Jump to:  A   |   B   |   C   |   D   |   E   |   F   |   G   |   H   |   I   |   J   |   K   |   L   |   M   |   N   |   O   |   P   |   Q   |   R   |   S   |   T   |   U   |   V   |   W   |   X   |   Y

Head Lice Growing Resistant to Standard Meds

Head Lice Growing Resistant to Standard Meds

FRIDAY, March 14, 2014 (HealthDay News) -- Most head lice found in North America now carry a gene mutation that makes them resistant to standard over-the-counter treatments, a new study cautions.

Head lice infestation is a major public-health issue, the researchers said, with roughly 10 percent of all American school-aged children missing school due to the intense itching and secondary infections that signal exposure.

The problem: Years of relentless exposure to a single treatment option has given rise to a surviving head lice population that is armed with what geneticists call "knockdown resistance," in the form of the TI genetic mutation.

This gives most of today's head lice an ability to withstand exposure to the main -- and previously effective -- ingredients found in most nonprescription head lice drugs: "pyrethroid" compounds such as permethrin.

"This isn't really controversial," said study co-author John Clark, a professor of environmental toxicology and chemistry at the University of Massachusetts, Amherst. "This is a problem we've been showing in development over a period of about 20 years. But our new work now shows that head lice are now almost 100 percent [knockdown resistant]. That means there's an awful lot of resistant insects out there in the U.S. and elsewhere."

Clark and his colleagues discussed their findings in the March issue of the Journal of Medical Entomology.

In the early 1990s, over-the-counter permethrin-based formulations entered widespread use, Clark said. Designed to kill lice by essentially short-circuiting their nervous system, such drugs became the standard of care.

But the seeds of permethrin's future failure were planted decades earlier, in the immediate post-WWII period, he said, when much of the population was first exposed to the pesticide DDT in an effort to reign in body lice infestations.

Head lice got caught up in the process, giving rise to a surviving population that silently, but increasingly, began to carry the protective TI mutation decades before the introduction of permethrin products, according to the study.

With that in mind, investigators set out to assess the current resistance status of North American head lice by conducting a genetic analysis of lice samples collected from 32 mostly urban locations across the United States and Canada.

DNA sampling revealed that more than 88 percent of the lice found in both countries carried the specific TI mutation that is associated with the kind of nerve insensitivity that makes lice resistant to standard over-the-counter permethrin medications.

In the United States alone, the researchers pegged TI frequency in an average of roughly 84 percent of the lice population between 1999 and 2009. But a closer look at the final years of this timeframe revealed that the rate actually began to approach 100 percent of the lice population between 2007 and 2009.

Accordingly, Clark and his associates concluded that the need for new treatments for lice has reached a critical stage.

"Europe and South America actually stopped using these pyrethroid compounds years ago," he said. "It's not that these compounds aren't in themselves good formulations. But the very last thing you want to do is treat a single pest population with one compound that has one mode of action for years and years -- and that's exactly what we did. The result is that these compounds are just not effective anymore."

"But the good news is that over the last three years we have seen four or five new compounds entering the market," said Clark, in reference to drugs that include the brands Ulesfia, Sklice and Natroba.

"They all have different kinds of compounds and mechanisms, and they're all already commercially available," he said. "This will lead to what's called redundant killing, where if one compound doesn't do the job, the other compound will. So there is a way forward."

Dr. David Pariser, a professor of dermatology at Eastern Virginia Medical School, in Norfolk, agreed about the need to update treatment for head lice.

"I completely agree with this study's assessment regarding resistance, and with the thinking about the new drugs that we now have available," said Pariser, a former president of the American Academy of Dermatology. "I've had personal experience with one of them, as I was involved in the clinical trials, so I know they're very effective."

"More than that, they can actually be easier to use, as the older drugs would have to be applied repeatedly, whereas the new drugs are typically a one-time treatment," he said.

"However, I would add one nuance," Pariser continued. "While these new agents are great, they are prescription drugs, which means they are more costly. It may not be the actual insured consumer who will feel it if he's only paying a co-pay for the new meds, but certainly it's going to be a much bigger cost to the health care system as a whole."

More information

For more about head lice, visit the U.S. Centers for Disease Control and Prevention.

SOURCE: John Marshall Clark, Ph.D., professor of environmental toxicology and chemistry, University of Massachusetts, Amherst; David Pariser, M.D., professor, dermatology, Eastern Virginia Medical School, Norfolk, and former president, American Academy of Dermatology; March 2014, Journal of Medical Entomology

Reviewed Date: --

Find a pediatrician
Dermatology
Dr. Judith Williams
Health Tips
Abuse of Prescription ADHD Drugs Rising on College Campuses
Cool Tools to Keep Your Kids From Smoking
Do Parents Influence Their Kids’ Health Behaviors?
Guidelines for Raising Smoke-Free Kids
Help Your Babysitter Prepare for Anything
Helping Children Conquer Fear
How Old Is 'Old Enough' for Contacts?
Parents-to-Be Must Communicate
Preparing Your Daughter for Changes
Reading to Kids Helps Their Development
Someone's in the Kitchen with Grandma
Talk With Your Kids About These Issues
Talking Sex with Your Teen
Teens and Talk: What's a Parent to Do?
We Can Head Off Teen Tragedies
When to Call the Doctor for Childhood Illnesses
Quizzes
Head Lice Quiz
Diseases & Conditions
AIDS/HIV in Children
Anatomy of a Child's Brain
Anatomy of the Endocrine System in Children
Anxiety Disorders in Children
Asthma in Children Index
Bone Marrow Transplantation in Children
Brain Tumors in Children
Chemotherapy for Children: Side Effects
Child Care
Diphtheria in Children
Discipline
Ewing Sarcoma
Firearms
Hepatitis B (HBV) in Children
Inflammatory and Infectious Musculoskeletal Disorders
Inflammatory and Infectious Neurological Disorders
Inguinal Hernia in Children
Insect Bites and Children
Kidney Transplantation in Children
Meningitis in Children
Mood Disorders in Children and Adolescents
Muscular Dystrophy
Myasthenia Gravis in Children
Osteosarcoma in Children
Pediatric Blood Disorders
Poliomyelitis (Polio) in Children
Post-Traumatic Stress Disorder in Children
Preparing the School-Aged Child for Surgery
Schizophrenia in Children
School-Aged Child Nutrition
Slipped Capital Femoral Epiphysis
Sports Safety for Children
Superficial Injuries Overview
Television and Children
Thalassemia
The Growing Child: 2-Year-Olds
The Heart
The Kidneys
Vision Overview
Whooping Cough (Pertussis)
Your Child's Asthma
Your Child's Asthma: Flare-ups

Disclaimer: This information is not intended to substitute or replace the professional medical advice you receive from your child's physician. The content provided on this page is for informational purposes only, and was not designed to diagnose or treat a health problem or disease. Please consult your child's physician with any questions or concerns you may have regarding a medical condition.