- Author: Siavash Taravati
- Posted by: Elaine Lander
Human lice (singular “louse”) are parasitic insects found on people. Adult lice are small (about 1/8 inch (3 mm) long or less) wingless insects that move by crawling. There are three species of lice that exclusively feed on humans: the head louse, the body louse, and the crab or pubic louse.
The head louse (Pediculus humanus capitis) and the body louse (Pediculus humanus humanus) are members of the same species, but the crab (pubic) louse (Pthirus pubis) is from a different insect family. All are pests of public health importance. Treatment is usually prescribed by medical professionals and should be focused on the infested person and their belongings. Use the following descriptions to identify these pests and help your clients seek out proper care from medical professionals.
These lice have a short, round body (not elongated), with hairy tubercles (small, knobby projections of the body wall) on the abdomen. The front legs are shorter and slimmer than the middle and hind legs (Figure 1). Adults and eggs are usually found on pubic hairs but may sometimes be found on other areas of the body such as beards, mustaches, eyelashes, and underneath the arms.
Head louse vs. body louse
Unlike the crab louse, these lice have elongated bodies (Figure 1) and lack tubercles on their abdomen. Head and body lice look almost identical since they are members of the same species. Positive identification requires consideration of specific morphological and behavioral differences (see Table 1). Body lice are known to transmit serious human diseases such as epidemic typhus, trench fever, and louse-borne relapsing fever. Head lice are not known to be an effective vector of diseases even when a pathogen is found in the louse's body.
Human lice elimination involves removal of lice from human body as well as from clothing and living environments. A head lice infestation on a person should be managed by the client. Head lice can be removed with a lice comb or treated with special lice shampoo or lotions containing one or more active ingredients. Human lice have developed resistance to many over-the-counter products containing permethrin or other pyrethroids. Therefore, it is believed that the most effective head lice treatment products are the ones containing ivermectin or spinosad. Body lice can be killed by dry cleaning clothing and bed sheets. Also, vacuuming and treating carpets may improve body lice management especially when the infestation is heavy. Body lice infestations can also be managed by reducing crowding and improving body and clothing hygiene. Head lice infestations, however, are not associated with poor hygiene, at least in developed countries.
For more details about the head louse, including thorough management options and guidance, see the recently revised Pest Notes: Head Lice.
Most people are practicing social distancing due to the current pandemic, so contracting head lice might not be a top concern right now.
However, many families with young children have at least one encounter with head lice at some time or another. Finding effective ways to manage these pests can be difficult, but it is possible. And remember, anyone can get head lice.
In the newly updated Pest Notes: Head Lice, authors Victoria Leonard and Dawn Gouge bring their public health and pest management expertise to the topic of head lice management, providing easy, safe, and effective ways to control a head lice infestation.
The authors state that while normal shampooing, hair-conditioning, brushing, and hair-drying will kill many lice, care givers should take action as soon as live lice are discovered. Treat the infested person's hair, then comb with a metal lice comb and clean the person's bedding and other belongings.
Choosing a treatment can be challenging since many common insecticidal shampoos no longer work well due to resistance. Regardless of the product chosen, always follow the label directions for safe use and reapplication. For detailed instructions on combing for head lice removal and discussion of prescription and non-prescription head lice treatments, consult the Head Lice publication.
Eventually, we will all return back to normal so we hope this information prepares you ahead of time dealing with head lice.
Although head lice can infest anyone, children are the most susceptible since they play together closely and share items that come into contact with the head like hats, headphones and combs. Head lice are not known to transmit infectious diseases and are considered more of a nuisance than a health risk. In many school districts, children with head lice are generally not allowed to attend school as long as nits are found in their hair.
An adult head louse is about the size of a sesame seed and ranges in color from tan to gray. While lice can crawl relatively quickly, they cannot hop, fly, or jump. This is why direct contact with an infested object or person is required to become infested. Because head lice live and breed completely in human hair, they only survive for about 1 to 2 days if they drop off a person. They cannot live on family pets.
Adult head lice and nits can be removed by combing with specially designed combs, head louse shampoos, cleaning areas around the house, and periodic head checks to detect reinfestation.