The Answer to Controlling Lice May Be in their Genes

Aside from the bedbug, one other blood-sucking creature has gotten a bad rap throughout history and is typically on the “least wanted” pest list: the louse. Common in schools and other communal living areas, lice seem to create trauma for the person they infest. Typically we associate lice with homeless people or anyone who lacks good hygiene, so when the eight-year-old daughter of a tenured faculty member gets lice, the infestation becomes an embarrassment to be eradicated as quickly as possible. The good news is that new research on lice genes may lead to some new control options.

There are three types of lice: head lice, body lice and pubic lice. Head lice and body lice are closely related; in fact, some scientists believe that head lice evolved from body lice. Body lice like to live in the clothing or bedding of someone who does not change clothing often. Head lice are prevalent in schools, mainly when children share hats or brushes, or when clothing is packed together in a small space.

Although body lice are typically found in conditions of poor hygiene, head lice can spread to anyone, no matter how often they wash their hair. Head lice are more of an indicator of how much a person shares head wear than they are of personal hygiene.

Unfortunately no amount of shampooing or bathing will rid a person of a lice infestation, no matter whether the lice are head lice or body lice. The person must instead wash with one of the common delousing products currently on the market. Delousing takes patience and often a few treatments. To complicate matters, lice have begun to develop resistance to some of the products, so louse victims sometimes have to try a couple of products before they find one that works. (see AgriLife Extension publication L-1315 for specific treatments)

That may change in the future, however, thanks to new research that has identified the genome sequence of body lice. A group of researchers from the U.S. and Europe discovered last year that lice has fewer sensory receptors than other insects and depend on an internal symbiotic organism for nutrients, making them vulnerable to new chemistries that can target those areas.

According to the study, lice have only 104 G protein-coupled receptors and 3 visual receptors, the smallest number of receptors discovered in any insect genome so far. They also have fewer odorant receptors. One reason for the small number of sensory receptors is that, unlike most insects that have to travel several feet or even miles to get to their next target, lice just “drop in” on their next meal. They don’t walk very far or jump; they typically travel between someone’s shirt and skin, or between a brush and someone’s hair. Live head lice usually live less than ¼ of an inch from the scalp. If you find lice or nits on someone’s hair, and it is more than ¼ inch away from the scalp, the lice are dead and the nits (eggs) have hatched.

Lice also contain symbiotic organisms called Riesa in their guts. The Riesa get their nutrition from the lice, and the lice use the Riesa to get vitamin B5. Although lice need vitamin B5, they can’t produce it themselves.

Authors of the paper produced as a result of the study hope that new pesticides can be developed to target either the Riesia or the sensory receptors.

The following are tips on avoiding and controlling lice:

To prevent lice:

  • Bathe daily and shampoo your hair several times a week.
  • Do no share hair brushes, combs, hats or hair accessories with others.
  • Machine wash bedding and clothing on a regular basis.
  • Lice like thick, long hair. If you have long hair, wear it tightly braided and comb it thoroughly every day.
  • Avoid close contact with anyone who is infested.

To control lice:

  • Seek help from a medical professional, including school nurses
  • When you buy a delousing product, follow the directions on the product label, including using the correct dose and applying it as directed. If the product does not work, switch to another with a different active ingredient.
  • A second treatment must be made 7 to 10 days after the first to kill newly hatched lice.
  • Comb the hair thoroughly with a lice comb.
  • Never use gasoline, kerosene, motor oil, household pesticides or pet shampoos.

News articles on the study:

Sequencing of the Human Body Louse Genome: Important Step Toward Control of Disease-Vector Insect (ScienceDaily, June 22, 2010)

Of Lice and Man: Researchers Sequence Human Body Louse Genome (ScienceDaily, June 22, 2010)

Genome Sequence May Lead to Better Methods to Target Lice (ScienceDaily, June 22, 2010)

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