Where Do Head Lice Come From?

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According to recent government statistics produced by the U.S. Center for Disease Control and Prevention, between 6 and 12 million school-age children contract head lice infestations every single year. And that’s just in the U.S.!

But where do head lice come from?

Head-to-head contact

Most of the time, head lice are spread from one person to another via direct head-to-head contact. However, they can also be passed around through sharing brushes or hats harboring live lice. Head lice aren’t fussy; they will happily live in clean or dirty hair.

Lice can’t jump, fly, or swim. They move from one host to another by crawling, clinging to the hair shaft with claws on the end of their legs. Once on the host, lice feed on the unfortunate person’s blood.

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Female lice lay eggs (nits) on the hair shaft close to the scalp where the temperature and humidity are ideal for the developing nymph inside the nit. Once hatched, the juvenile louse feeds for a week or so, when it then becomes mature enough to breed. And the life cycle starts all over again.

Head lice are an exclusively human parasite that has evolved to feed only on human blood. So, you can’t blame your dog or cat for bringing lice into your household!

That’s how lice are spread from one person to another, but where did these nuisance parasites originate from?

Where do head lice originate?

It’s thought that head lice evolved from body lice tens of thousands of years ago when humans began to wear more clothing. Scientists believe that present-day head lice first appeared in North America and Asia. As people became more mobile and able to travel long distances, they spread across the globe to Australia and Europe .

Evidence of head lice has been found on ancient, mummified human corpses, and head lice are described in ancient Greek, Roman, and Egyptian medical texts.

Examination of head lice DNA has been used to trace modern head lice to a common ancestor that first appeared around two million years ago. So, despite being a public menace, the humble head louse has provided us with important information about the evolution of the human species. 

How? Well, head lice can only live on human hosts, feeding exclusively on human blood, and are unable to survive for more than 48 hours following separation from the host. Their DNA, therefore, provides a pure link to the evolution of modern humans.

The future of head lice

Like most species, lice continue to evolve. In fact, these plucky little creatures are becoming immune to many of the chemicals used to combat them. For example, multiple medical studies have shown that most lice have now developed a resistance to pyrethroids, the active insecticide that’s used in many over-the-counter lice-killing shampoos and treatments.

However, the best and most effective treatment for head lice is still a combination of louse-killing shampoo and a high-quality nit comb. You will probably need to repeat treatments over the course of a month or so to kill off emerging nymphs. Head lice are notoriously difficult to eradicate, which is perhaps one of the reasons they have survived and flourished for such a long time.

Wrapping it up

So, where do head lice come from?

  • Over thousands of years, head lice have evolved to feed exclusively on human blood. They live and breed close to the humid, temperate area of the scalp and laying their eggs on the hair shafts.
  • Lice can’t live on animals or survive away from their food source for more than 48 hours.
  • When someone contracts head lice, 95 percent of the time he or she caught them by direct head-to-head contact with another person.

Parents whose children have head lice should keep their kids away from school until the lice have been eradicated. That’s the only way to prevent an epidemic from rampaging throughout families and spreading throughout whole communities.