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Head lice trigger body lice epidemics, study finds

You can stop scratching your head about the origins of human body lice.

Body lice, which cause highly lethal epidemics (trench fever, typhus and relapsing fever Borrelia), originate from head lice, an international group of scientists reported today.


Image of body louse (Pediculus humanus humanus) courtesy of CDC

 The discovery indicates that it is not possible to eradicate body lice without first eradicating head lice, which until now has proved impossible, according to the researchers.

“This has recently been shown by a team from the Emerging Infectious and Tropical Diseases Research Unit (CNRS/IRD/Université de la Méditerranée), in collaboration with researchers from the Universities of Florida and Illinois” in the U.S., says a news statement released by the French National Center for Scientific Research (CNRS).

The research is published in the March 24 issue of the journal PloS Neglected Tropical Diseases.

“Until now, head lice, which feed on the scalp and lay their eggs on hair, and body lice, which feed on the rest of the body and live in the creases of dirty clothes, were thought to be different species. However, researchers from the Emerging Infectious and Tropical Diseases Research Unit (CNRS/IRD/Université de la Méditerranée) and two U.S. teams have shown that these lice have the same origin,” CNRS said.


Image of head louse (Pediculus humanus capitis) courtesy of CDC

Through genetic analysis of the louse genome, the researchers observed that “it was impossible to distinguish the head louse from the body louse at the genetic level,” CNRS added.

“In addition, fieldwork has shown that, in populations living in extreme poverty, the proliferation of head lice led to the emergence of lice able to adapt to clothes and turn into body lice. These body lice were then able to cause epidemics of body lice and bacterial epidemics.”

“This discovery shows that it is not possible to eradicate body lice without first eradicating head lice, which until now has proved impossible. In addition, this explains the regular appearance of body lice in areas where they were previously unknown, when sanitary conditions rapidly deteriorate.

“Head lice are therefore permanently in an endemic state. In highly unfavorable sanitary conditions, head lice proliferate, and some of them migrate into clothes, triggering a new epidemic of body lice,” CNRS said.

Life cycle of the head louse

Information provided by U.S. Centers for Disease Control & Prevention

The life cycle of the head louse has three stages: egg, nymph, and adult

lice-lifecycle-illustration.jpgEggs: Nits are head lice eggs. They are hard to see and are often confused for dandruff or hair spray droplets.  Nits are laid by the adult female and are cemented at the base of the hair shaft nearest the scalp (no. 1 in the illustration above). They are 0.8 mm by 0.3 mm, oval and usually yellow to white. Nits take about 1 week to hatch (range 6 to 9 days). Viable eggs are usually located within 6 mm of the scalp.

Nymphs: The egg hatches to release a nymph (no. 2). The nit shell then becomes a more visible dull yellow and remains attached to the hair shaft. The nymph looks like an adult head louse, but is about the size of a pinhead. Nymphs mature after three molts (no. 3, no. 4 ) and become adults about 7 days after hatching .

Adults: The adult louse is about the size of a sesame seed, has 6 legs (each with claws), and is tan to grayish-white (no. 5). In persons with dark hair, the adult louse will appear darker. Females are usually larger than males and can lay up to 8 nits per day. Adult lice can live up to 30 days on a person’s head. To live, adult lice need to feed on blood several times daily.  Without blood meals, the louse will die within 1 to 2 days off the host.

How do you get head lice?

Getting head lice is not related to cleanliness of the person or their environment, according to the CDC.

“Head lice are spread by direct contact with the hair of an infested person. The most common way to get head lice is by head-to-head contact with a person who already has head lice. Such contact can be common among children during play at school,  home, and  elsewhere (e.g., sports activities, playgrounds, camp, and slumber parties).

“Uncommonly, transmission of head lice may occur by wearing clothing, such as hats, scarves, coats, sports uniforms, or hair ribbons worn by an infested person; using infested combs, brushes or towels; or lying on a bed, couch, pillow, carpet, or stuffed animal that has recently been in contact with an infested person, the CDC says.


  1. Phil
    October 11, 2014, 3:59 am

    @ least their not scabies, have had a bit of a scare trying to find out what it was. Noone could help, Drs, Gov, Lsns, Exterminatior u name it. Was researching on the microscope and finally got the the bottom of this. Now it’s prsyers to try to eradicate them. Been since July been living a nightmare!

  2. clarence
    August 14, 2014, 3:44 am

    Like me friend said: “Even the toilets gotta Eat but lice will be the reason we turn to Zombies. Watch. Lice that turn u in to a flesh eating zombie 🙁

  3. sandra
    January 24, 2014, 10:51 pm

    My daughter and I were infected with lice 6 months ago. I have tried every possible treatment including oral treatment of stromectum/Ivermectin. I comb my hair between 2 to 4 hours a day. When l took the ivermectin, I simultaneously treated my hair with non toxic Clear lice product. Since I could still feel them a week later. I actually left a perimthin shampoo in my hair overnight. The next morning the lice moved to my body and now have these creatures getting into the hair follicles of my skin. They are still in my hair and I have stopped treating my hair so that they will move away from my body. The more agressive I got, the more agressive they got. I used so many bottles of olive oil and vinegar to aid in coming them out but to no avail. I did not know they could mutate to adapt to skin. I spend so much time cleaning and combing that have not been able to devote adequate attention to my daughter’s hair. But as it turns out she only has a few nits and they have not moved to her body. These nits are extremely small and the adult stage bug is 1/2 centimeter long at best. Is this a super lice or somthing totally different? A mitosis of the bug?
    – Exhausted and Depressed

  4. Dawn M
    August 11, 2013, 6:01 am

    Debbie, they are living in your bed or furniture, if you are becoming reinfested. Spray ALL furniture, beds, pillows, cars, pet bedding. Vacuum thoroughly all carpers and furniture. Wash all bedding in HOT water & dry on highest possible temp. Put things you can’t wash (stuffed animals, decorative pillows) into bags out in the sun. Run all your brushes & combs through the sterilize cycle if your dishwasher, or soak them in water that is boiled on the stove. Re-treat in one week, and again , every week for 2-3 months.
    As a teacher, I see this often, and the biggest reason they return is failure to treat the entire house, even if you can’t see them. Also, put about 20-30 drops of Tea Tree Oil in your shampoo and conditioner. It isn’t exactly a pleasant smell, but it is better than the chemicals to treat lice, & it can help prevent them.
    Good luck eradicating them.

  5. Stepf
    June 24, 2013, 7:02 am

    Debbie…we use Neem Oil added to our conditioner…works a treat – about 10 drops in normal amount of conditioner, leave on about 10 mins & comb wit lice comb before rinsing out then comb again once rinsed. we do this once a week. Neem oil kills the eggs & lice, & leaves your hair with a nice shine 🙂 can be bought from Health food shops
    there is another remedy…
    Coconut oil + apple cider vinegar to treat head lice. … Coconut oil dissolves the lice’s outer skeletal shell instantly. So once you put it on someone’s head you can have them shower and rinse it off right away and all the lice will be killed and gone! Plus there are no chemicals!

    Here is what to do

    Getting lice in the family is truly horrifying & if you don’t get rid of them ASAP, they will get into everything & literally take over. Not fun. The really important thing is to find an effective treatment that doesn”t require putting harsh chemicals onto your head, which then get absorbed into your body. Yuck. So, here is a tried & tested effective remedy to wipe out those critters in one foul swoop!You will need: A jar of coconut oil & a bottle of apple cider vinegar.

    First, rinse your hair with the vinegar, don’t wash it out, leave it in until it dries. The vinegar dissolves the ‘glue’ which sticks the eggs to your hair follicles. When the vinegar has dried, pour coconut oil into your hair, making sure you get complete coverage. Cover your hair with a shower cap or hair wrap & leave it in for the whole day, as it will take a few hours for the coconut oil to smother & kill the lice. Comb your hair to get as many of the eggs & lice out as possible and then shampoo as normal. You only have to do this once, it really works & no chemicals! Oh, & the coconut oil makes your hair beautiful & shiny, so your getting a lush hair treatment at the same time!
    Hope either one helps with your problem 🙂

  6. debbie
    June 14, 2013, 3:26 pm

    I got headlice from my g.daughter whch is in grade school!! They were able to get rid of theirs however,I have done everything from cleaning to all over the counter products,all natural products and am now on my 3rd different prescription and nothing is working so I shaved my head and I still have them!!! I have the bites to prove it!! Now they are traveling all over me!!!! Can someone please help me??? I don’t know what to do!!!