STOWE, VT. — Location, location, location. Where lice live on the body and how they got there are important considerations for optimal diagnosis and therapy, according to Dirk M. Elston, M.D.
While much attention is given to the identification and treatment of head lice because they are hyperendemic in many areas of the world, body lice and pubic lice are unique entities with specific treatment requirements, Dr. Elston said at a dermatology conference sponsored by the University of Vermont.
Similar in appearance to head lice, body lice (Pediculus humanus corporis) live in clothes and bedding rather than head hair. Scratch marks, hives, and small raised red bumps on the shoulders, torso, or buttocks are possible signs of body lice infestation.
Unlike head lice, body lice can be vectors for blood-borne diseases such as typhus and trench fever. In the United States, body louse infestation mainly affects homeless populations, said Dr. Elston of Geisinger Medical Center, Danville, Pa.
Body lice infestations are treated by removing the clothing, laundering it in hot water, drying it on high heat, or pressing it with a hot iron. However, these tactics are often not feasible in outbreaks in other parts of the world, Dr. Elston said. In some settings, treating clothing with DDT, permethrin, or fumigants is useful. In addition, single-dose ivermectin has shown promise for mass treatment, and pediculicides may be effective against body lice.
Pubic lice (Phthirus pubis) are distinct in appearance from head and body lice; they have short crablike bodies. While they are most frequently found in the pubic region of the infested person, where they can cause intense itching and redness, they may also be found in other areas, such as in facial hair or eyelashes. In fact, Dr. Elston said, “I am amazed at how often it is misdiagnosed. When you see eyelash nits, you should be looking south, not north,” he stressed.
Pubic lice infestation occurs mainly through sexual contact, but may also be acquired by sharing a bed. Children usually contract pubic lice from an adult, which should be investigated, he said.
However, pubic lice help to solve crimes “There is enough blood in a single louse to identify a rapist's DNA by [polymerase chain reaction],” he said. Because the pubic louse egg “is relatively impermeable, the best way to get to it is through the [host's] blood,” Dr. Elston said. Toward that end, oral sulfa drugs as well as ivermectin have been used successfully.