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Diseases > Lice

The topic of louse-borne disease is complex and presentation of information pertaining to it requires the use of technical terms. These terms are depicted in bold type and are explained in the glossary.

Only one type of human louse is a vector of disease agents, the body louse Pediculus humanus. It is a vector of three species of bacteria that cause three different diseases in humans: epidemic typhus fever, epidemic relapsing fever, and trench fever. The head louse, Pediculus capitis, can be infected with these disease agents and transmit them in the laboratory, but head lice are not known to be vectors in nature. The pubic louse, Pthirus pubis, is not a vector. This section covers all three diseases, but only epidemic typhus fever might in the future be transmitted in Indiana.

Nearly every insect-borne and tick-borne disease is a zoonosis. A disease that is a zoonosis can infect humans, but exists in nature in a non-human animal reservoir. Louse-borne diseases differ, however, in that humans are the only reservoir hosts, with one apparent exception (see below).

What Should I Know About Body Lice and About Their Control?
Body lice are permanent parasites of humans and typically cannot survive off a human host for longer than a few hours, and then only under optimal temperature and humidity. Spread of body lice requires direct contact with an infested human or sharing of louse-infested clothes. However, body lice will abandon a person with a high fever and can crawl across surfaces and infest a nearby individual.

Control of body lice typically involves the use of an insecticide together with the mechanical removal of eggs and lice, plus sanitation of infested clothes and bedding. Insecticides known as "pediculicides" include over-the-counter products and physician prescribed medications that are applied to humans. For information on controlling body lice and for specific chemical control products refer to the Web site of the Centers for Disease Control and Prevention (CDC) and discuss treatment options with a physician. It is essential to apply products exactly as directed on the label AND as directed on the prescription. It is important to note that eggs of body lice are not killed by insecticides, and a repeat application typically is required in 7-10 days to kill newly hatched larvae. Infested clothing and bedding should be washed at a minimum of 130 degrees Fahrenheit and then dried at a high temperature for 20 minutes in a clothes dryer. Items that cannot be washed require dry-cleaning.

What Diseases Do Body Lice Transmit?
The following accounts provide specific information pertaining to louse-borne diseases. The key points are presented for quick reference and comparison. For example, the disease agents of epidemic typhus fever and trench fever are transmitted via infected feces of body lice whereas the disease agent of epidemic relapsing fever is transmitted via infected fluids of body lice that have been damaged by scratching. Thus louse-borne disease agents are not injected by mouthparts when lice take a blood meal.

Where Can I Find More Information on Human Lice and Louse-Borne Diseases?
The following Web site contains accurate and current source of detailed information on human lice and louse-borne diseases.

A recent (2002) textbook by G. Mullen and L. Durden, Medical and Veterinary Entomology, has an excellent chapter devoted to lice and louse-borne diseases that covers biology, behavior, medical and veterinary risk, and general information on prevention and control. A classic book (1935) by H. Zinsser, Rats, Lice, and History, provides an interesting account of the impact of louse-borne diseases on human history.

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