April 1946 E-685 United States Depa2*taent of Agriculture Agrioultural Research Administration Bureau of ieitomology and Plant Quarantine CONTROL OF EUUAH LICE By Gaines W, Eddy and Raymcnd C. Bushland Division of Insects Affecting Idon and Animals Three kinds of lice attaftlc man— the body louse ( Pediculus humanus corporis Deg.)^ the head louse (P, humanus humanus L.), and the crab or pubic louse ( Phthlrus pubis (L.)). These lice are world-wide in their distribution and all are foxrnd in the United States, Fl%m a medical viewpoint the body louse is most important, because in many parts of the world it Berres as a vector of diseases, the most serious being epidemic typhus. Louse-borne diseases are extremely rare in the United States and, as infestations of the body louse iii this ootyarisry are usually limited to vagrants, it causes less domestic con- cern than do head and crab lice. Head lice have been proved capable of transBiitting typhus under experimental conditions, and therefore are important from a health standpoint. Crab lice are not known to transmit disease. The head louse apd the body louse are similar in appeea-ance, the Tarieties being distinguished only by their location on the host. An adult body louse (fig^. 1) is grayish in color and about one-foyrth inch long; the iamature stages, or nyn^hs, are smaller, but even newly hatched lioe are visible to the naked eye. A crab louse (fig. 2) is shorter and Buoh flatter and broader than a body louse. Its crablike shape accounts for its oonmon zuune. The aggs^ or nits, of human lice are all similar in appearance. Th^ are whitish in color, and are often more noticeable than the lioe. The presenoe of eggs is frequently used as an index of infestation when •xwil nations are made by doctors and nurses. The life oyoles of all three kinds of lice are similar. Ordinarily •S(s hatch in about 8 days cd^fcer they are laid, but eggs somewhat re- aOT*d froB the body dew lop bio re slowly at lower temperatures and ittoabation tOKpetimes requires 2 weeks. Head and body lice spend about 9 dfa in th« oynphAl stages, melting (shedding their skins) three times as tlMy grow to adults. Crabl lice develop more slowly than do the other «peei«s« The feaalea begin laying eggs about 1 day after they have •nergod as adalts. A female louse may live as long as a month, laying 4 or 5 eggs day. Lnmature lloe usually stay close to the skin, from whloh they suok blood, whereas sexually mature lloe are more migratory. Fully fed, mated females frequently wander about on the clothing and do not seek the skin again until they beoome hungry, Hhen people are olosely assoolated in situations such as are oomnon in schools, barraoks, or publio oonveyanoes, this habit of the lide makes for a rapid spread of infestations. Body Lice The body louse lives in the clothing and risits the skin several times daily ta feed. The undergarments are most heavily infested, but some lioe can usually be found in the outer clothing. Ordinarily the eggs are deposited exclusively on the clothing, thk seams and folds being preferred. The eggs are usually glued to fibers of the oloth, but sometimes they are fastened to hairs on the body. Persistent infestations by the body louse are always associated with poor sanitation. Control of this insect among civilians is best accomplished by providing adequate laundry facilities and sufficient clothing for a weekly change. Either washing in hot water or dry cletuaing infested garments kills all stages of lice. If all indi- viduals change to clean clothing once a week, oomplete control is assured. Because the body louse lives in the clothing rather than on the body, this insect is easier to control than are the head louse and the crab louse. If some member of an average jUnerioan' family should happen to beoome infested with body lioe, no special procedure is necessary to protect the family if the infested person follows the directions given above. If, as rarely happens, a few lice or eggs on the indi- vidual's body should escape immediate destruction, they camot survive to build up an infestation in a home where ordinea*y oleanliness is practiced. Eradication of the body louse from any group of people is now practicable because of the development of insecticides possessing residual action. One of the most satisfactory materials is a louse powder consisting of 10 percent of DDT in ^rophyllite or talo, irtiich was developed at the Orlando, Fla,, laboratory of the Bureau of Entomology and Plant Quarantine, One o\anoe of the powder should be applied over the inner surface of underclothing, and an additional 1/2 to 1 ounce to the seams of tlje outer garments. Underwear thoroughly treated in this way continues to kill lice for about a month's W3aring thereafter. When the DDT powder is properly applied to the clothing of all individuals in an infested coiominity, a single application will eradicate the lice. -3- louse powder oan be effeotlvely applied "with any fluacvr type of container, but lat-ge groups of people oan be nore arftpidly M>d effi- ciently treated by delousing oreirs using stazidard iiiMotlolde dairkers. The Army found that either hand-operated or pover dusters gave good results and that for suoh treataient It was not neoessaxy for oirllians to remove their oxothJ!|ng. The noszle of the duster should be inserted through openings in the olothing and the pordar applied to the skin aad between layers of clothing. I/Vhen meohanloal equipment is used, at least 2 ounces of powder ^ould be applied to each person being treated. If only a few individuals are to be treated, a satisfactory duster can be made from a small Jar or oan having a metal iiS by punching a ftw holes in the oover. The- use of insecticides is essential for the eontrol of head lioe, because these inseots can withstand frequent shaiqiooing with soap tad water, and it is alaost impossible to remove all lice and eggs by ooabing and brushing the hair. The 10-peroent DDT powder is also effective against the head louse, but beoause the residue may be visible in the hair a liquid materied known as the SBIN formula, which was also developed at the Orlando laboratoxyj is preferred. If the DDT powder is used, it should be applied either with a mechanical duster or with the shaker type of oontainer, the BMthod of application depending somewhat on the number of poraons to be treated. The dust should always be thoroughly applied. Since DDT does not affect the eggs, the powder should not be washed from the hair for at least 10 days after treatment. If left in the hair, the powder will kill yoimg lice as they hatch from the eggs. If an individual user prefers to wash his hair on the day after treatment, a seoond application should be made 8 to 10 days after the first. Although the NBIIJ formula was developed during the war for use against the body louse in conjunction with certain other control measures, it should find greater use in peacetime against the head and crab louse. The formula may be prepared in concentrated form and diluted with water as needed. The UBIH oonoentrate consists of the following ingredients: Head Lice Percent by weight Benzyl benzoate Sorbitan nwnooloate polyoxyalkylene ether 68 14 derivative (Tween 80 ) Benxocaine ... . . DDT 12 6 4. To prepare an emulsion, 1 part of the conoentrate should be diluted with 5 parts of water. This mixture should be shaken thoroughly before it is used. The method of applying the material is not so important as doing a thorough job. The eggs must be oontaoted to be killed. To make sure thet this is done the hair should be wet, or at least moistened throughout. Combing the hair following application tends to insure a more even distribution of the treatment. If properly applied, this material will kill all lice and eggs present in the hair, and the residual effect will last for 2 weeks or more. Even though all the lioe and eggs in the hair are killed, there may be live lioe or viable eggs present in the olothing, headwear, or aJaout- the home which may oause a reinf estation if the hair is washed too soon after treatment. To make fairly certain that lioe are com- pletely eradicated, the material should be allowed to remain in the hair for at least 8 to 10 days. The treatment can be used effectively as a prophylactic if an application is made every 2 or 3 weeks. Other remedies, such as larkspur lotion and kerosene in either vinegar or olive oil, and derris powders and lotions, have been widely used against head lice. These materials are not ovicidal and do not have long-lasting properties; therefore, two or more treatments are required. They are not recommended unless the DDT or th^ liBIN formula is not available. Crab Lioe Sanitation is much less important in the prevention and control of the orab louse than it is for the body louse. The crab louse lives in the hairs of the body rather than in the clothing, and therefore re- laoving and disinfesting the garments will not free the person of lioe; it is necessaiy to use insecticides. Crab lice can be conveniently and effectively controlled with two treatments of the 10-percent CDT powder. The second application should be made about 8 to 10 days after the first. All hairy portions of the body, including the arms, armpits, chest, the pubic and perineal region, and the legs, should be thoroughly dusted and the material irubbed in with the fingers. The user should not bathe for at least 24 hours after applying the treatment. The NBIN formula is also effective against the crab louse, A single application has been found to eradicate an infestation, ^is material should also be applied thoroughly to all hairy parts of the body and rubbed in well. Application me-y be made with any absorbent material -5- or by hand. If large numbers of individuals are to be treated, a sprayer with a paint-spray nozzls may be found oonvenient, The treat- ment should be allowed to remain on the body at least 24 hours to prevent a possible leinfestation from lice in the bedding or other plaoes. Several other remedies have been used against crab lice in the pasty including blue ointment, kerosene in vinegar or olive oil, and derris and larkspur lotions, Diese materials are inferior to the DDT powder or the NBIN formula and are no longer recoiranended, Derris powder or preparations containing kerosene are irritating to the tender parts of the body and should not be used in crab louse oontrol* UNIVERSITY OF FLORIDA 3 1262 09238 7280 i