;ic; ( l-f L Agricultural ~nsion Service • University ~f lMinnesota

UNIV:::ESITV OF M!NNCSOTA DOCUMENTS

JAN t. :.. 1Si:3 L-./ l ENTOMOLOGY NO. 46-1976 -DAVID M. NOETZEL ST. PAUL C.l,MPUS L!BRARl:CS :ontrol of Lice on Humans

Outbreaks of lice on humans are historically associated The Body Louse with periods of social upheaval, such as wars. However, in re­ The body louse is capable of carrying epidemic typhus cent years lice have again become abundant in societies with from human to human. The first use of DDT was to control relatively good sanitation standards, probably because of body lice so typhus could not be spread. Severe infestations changes in living patterns. Lice problems don't have to occur also cause darkened and hardened skin, called "Vagabond's because excellent control procedures are available. disease" in humans. Three kinds of lice can be found on humans. The head louse and body louse are closely related. The crab louse is dif­ ferent from the other two in appearance and behavior. None of these three is found on any animal other than humans. The Head Louse Diagnosis of head lice is usually based on finding the eggs, or "nits" as they are also known, attached to the human hair, usually behind the ears and at the nape of the neck. How­ ever, eggs have been found on eyebrows, armpits, and even the chest. Less frequently they attach to caps and scarves. Positive diagnosis should be made by an entomologist, physician, or public health worker, because hair spray residue and naturally occurring flaking skin have been confused with eggs.

Nit or egg of head louse attached Adult body louse to head hair

The body louse is very similar to the head louse in size and appearance. In behavior it tends to move from the host to clothing and back again. Eggs are laid on clothing fibers and all stages of the louse appear in clothing. The adult head louse is 2-3 mi Iii meters long, and dirty The life cycle, from egg to adult, takes about 3 weeks. white to grayish black in color. There is a tendency for lighter­ The adult body louse can survive no longer than 10 days off the colored lice to be found on fair-haired individuals. host. All stages, including eggs, will die within 30 days after The female head louse lays 50 to 150 eggs which hatch leaving the host. in 5-10 days; the life cycle is 2-3 weeks. The head louse Transfer of body lice from person to person can occur spreads from person to person, usually by contact. However, through bodily contact. Lice and eggs may be transferred transfer can also take place through sharing combs and head­ through exchange of clothing. Less frequently the louse can be wear. picked up by using towels, bedding, etc., in common. The Crab Louse First indications of a crab louse infestation are itching Because both body and head lice can be transferred on and annoyance to the human. The louse itself, grayish-white clothing, it is not a good idea, for example, to exchange cloth­ to pink, may go undiscovered for some time. Often pustules ing, to share combs or brushes, or to use towels in common. form where lice bites occur and a severe skin reaction can de­ Once an infestation is discovered, it is desirable to use an velop. insecticide to kill both lice and eggs. Do not use an insecticide, however, unless the problem is positively diagnosed as human lice. Obtaining medical advice is recommended. In fact, some insecticides require a prescription. Nonprescription insecticides which can be used for human louse control include A-200 Pyrinate, Cuprex, and Bornate. Prescription insecticides include Topocide and var­ ious Kwell preparations. When any of these compounds is used as directed, it can be extremely effective in killing both eggs (nits) and lice. The dead nits can be removed from the hair by combing with a fine comb. Together with insecticide treatment for body and head lice, clothing and bedding should be washed in hot water, tem­ perature 125° F ., for 10 minutes. Modern clothes dryers greatly exceed this temperature and work well to help kill lice and eggs. The close social contacts of the person infested with lice should be informed of the possibility they might have picked up lice from this person (or vice versa). This helps to prevent further spread and also stops spread back to the individual who Pubic louse (adult, female) has already successfully controlled the lice. Also to curtail spread, it is particularly important that school nurses or teach­ The louse is remarkably adapted for attachment to coarse ers be informed of any incidence in school-age children. body hairs. Usually it is found in the pubic and perianal areas, but it has been found on other body areas including the eye­ Remember: Insecticidal control of lice should only be brows and eyelashes. It is most unusual to find the crab louse carried out following positive identification of the lice. Insec­ anywhere but on the host, unless the louse is rubbed off or is ticides are poisons and their application to the human body carried off with a body hair. It dies after 24 hours if it is not should be considered carefully. Use the insecticidal prepara­ attached to a human. tions precisely as directed, avoiding application to mucous Eggs attach to the base of hairs and require a week to membranes and eyes. Insecticides used as directed and accom­ hatch. A newly hatched louse grows to adulthood in about panied by proper sanitation are very effective in ending lice 3 weeks. The adult may survive for a month or so on the infestations. host. It is well to avoid lice infestation. However, people who Crab lice are usually transferred from person to person experience a problem but effectively cope with it, should be through sexual contact. Some transfer may occur where two praised not condemned. This is an important element because people sleep together or maintain other somewhat prolonged part of an effective control program is to warn those to whom bodily contact. Although various writers suggest transfer might the lice might have spread. An early medical entomologist said, occur in other ways, data do not support such contentions. "it is no disgrace to have lice, but it is to keep them." Treatment of Human Lice Infestations "An ounce of prevention is worth a pound of cure" in lice control. To reduce the chances of getting lice maintain The information given in this publication is for educational good standards of cleanlines. This includes regular washing purposes only. Reference to commercial products or trade of self, clothes, and other items such as bedding. Keeping hair names is made with the understanding that no discrimination trimmed and neat and changing wearing apparel daily are also is intended and no indorsement by the Minnesota Agricultural desirable cleanliness habits. Extension Service is implied.

Issued in furtherance of cooperative extension work in agriculture and home economics, acts of May 8 and June 30, 1914, in coopera­ tion with the U.S. Department of Agriculture. Roland H. Abraham, Director of Agricultural Extension Service, University of Minne­ sota, St. Paul, Minnesota 55108. We offer our programs and facilities to all people without regard to race, creed, color, sex, or national origin.