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SECTOR WIEWS Vol. 18 No. 5 May, 1971

-311^ UNDERSTANDING,6 AND TREATING OF LICE ON HUMANS Benjamin Ken and John H. Poorbaugh, Ph.D.

Infestation with human lice, or , Therefore, sucking lice found established still occurs even in societies with generally upon humans can only be human lice, of which high standards of sanitation. Public health there are three distinct kinds: head lice, body agencies may become involved if infestations lice, and crab lice. More than one of these include or expose a substantial number of peo- kinds may infest a person at the same time. ple, which occasionally happens especially at public institutions such as Jails, schools, The common and scientific names of human and state or county hospitals. lice now accepted by the Entomological Soci- ety of America (Blickenstaff, 19 70) and sever- This compilation is presented as a guide al common synonyms found in the older litera- to the accurate and recognition proper treat- ture are: ment of those occasional infestations of hu- man lice which still annoy and potentially 1.) head Pediculus humanus threaten our citizens. capi- tis De Geer

Identification and Biology of Human Lice synonym Pediculus capitis De Geer

Human lice are part of a rather large group 2.) Pediculus humanus hu- of known as sucking lice which are manus Linnaeus permanent parasites on the bodies of mammals synonyms Pediculus humanus corpo- throughout the world. These insects spend ris De Pediculus corporis De their entire life on the bodies of their animal Geer; Geer; Pediculus vestimenti Nitzsch hosts where they suck blood for nourishment and obtain necessary moisture and warmth. 3.) Pthirus pubis (Linnaeus) The eggs of lice, which are called nits, are attached to the hair of the host, and in the synonyms - Phthirus pubis (Linnaeus); c ase of the human body louse, to clothing Phthirius pubis (Linnaeus); Phthirius fibers. Many different kinds of sucking lice inquinalis Leach are found on warm-blooded animals through- out the world, and each kind of louse is close- It is important that an accurate identi- ly adapted to and is often restricted to a cer- fication of the louse involved be made so that tain kind of animal. Human lice can establish the most effective treatment and preventive and maintain themselves only on humans. measures can be recommended. In some in- stances, errors in diagnoses of pediculosis Vector Control Specialist, Bureau of Vector Con- have been made on the basis of inconclusive trol and Solid Waste Management, California State evidence, particularly when head lice have Department of Public Health. been suspected. Head lice and body lice are different forms The usually attaches the nit (subspecies) of the same louse species, Pedi- close to the base of the hair about 1 mm from culus humanus, and are superficially similar the scalp (Nuttall, 1918). The hair is assumed in appearance, but both are easily distinguish- to grow at the rate of 0.4 mm per day (Mellan- able from the crab louse with the aid of a mag- by, 1942). Since the nits of the head louse nifying glass. Body and head lice have the hatch in about nine days one would expect three pairs of legs about equal in size, and the most of the unhatched nits to be within 5 mm abdomen is distinctly longer than wide (Figure (about 3/16 of an inch) from the scalp. Empty 1). The crab louse has the middle and hind shells which lack the cap and are no longer legs and claws greatly enlarged, and the abdo- turgid to the touch are likely to be farther men is wider than long, giving the creature a from the scalp. crab-like appearance (Figure 2). The nits of head lice (Figure 3) and body Adult body and head lice are approximately lice (Figure 4) are quite similar in appearance, 2 mm (males) to 3 mm (females) in length and but those of crab lice (Figure 5) are slightly vary in color from dirty white to greyish-black. smaller, have prominent respiratory globules Head lice can adapt their coloration somewhat on the cap, and have a longer cement attach- to the hair color of the host, so that lice from ment on the hair.. The fact that the nits are blondes tend to be paler than those from peo- cemented at an oblique angle to the hair ple with dark hair. Body lice and head lice are (like a stubby branch) is very helpful in dis- quite similar in appearance, and even an ex- tinguishing them from foreign material which pert will have difficulty in positively distin- frequently surrounds the hair and may readily guishing between all specimens of the two on slide up and down. the basis of morphology alone. However, t heir habits differ significantly. Head lice. almost Lice, as well as hairs bearing louse nits, always live in the head hair and attach their can be preserved in alcohol and submitted to nits (eggs) to the hair. Body lice prefer to live an entomologist for identification or verifi- in the clothing and attach their nits-to cloth- cation of a diagnosis. The Bureau of Vector ing fibers (infrequently to the body hair). Control and Solid Waste Management will make such determinations for California health per- Adult crab lice are greyish-white to slight- sonnel. ly pink and are only about 1 mm long. Crab lice mainly infest the pubic hair, occasionally the The body louse: The body louse has been the hair elsewhere on the body, and attach their object of much attention. It alone, among the nits only to hair. three kinds of human lice, has been definitely implicated as a vector of louse-borne relaps- Immature lice (nymphs) look very much ing fever and epidemic . Historically, like the adult but are smaller. There are three the massive epidemics of louse-borne diseases growth stages or instars between the nit stage were transmitted by large populations of body and the adult. Immature crab lice are easily lice which infested people living in unsanitary separable from immature head lice and body conditions, especially during times of famine, lice, but the young of head lice and body lice disaster, or war. Although there is some ex- look very much alike. perimental evidence that both the crab louse and the head louse might serve as vectors, Human lice attach their nits firmly to hair their actual role as such has not been estab- or clothing fibers by a ring of cement. The lished. Neither of the two louse-borne diseases nits are about 0.8 mm long and 0.3 mm wide, has been reported in the United States for the thus two nits placed end-to-end would cover past 35 years. The bites of the body louse are the diameter of the head of an ordinary pin. annoying, and the skin of persons who con- The nits are oval in shape and yellowish opal- tinuously .harbor these lice becomes hardened escent in color. Each nit has a cap (operculum) and darkly pigmented, a condition known as which comes off intact when it hatches. After "vagabond's disease". the nit has hatched, the cement-like attach- ment and empty shell may remain on the hair. All stages of body lice are found on cloth- These empty shells are not easily removed by ing. The adults and nymphs move to the skin shampooing or washing, and thus are useful at intervals to feed and are most numerous in diagnosing lousiness even if hatched lice where clothing is in continuous close contact are not located. with the body, such as the armpits and belt- It 1 JAN107? 24 I mm

FIGURE 1 FIGURE 2

Pedicalus husnanus capitis, head louse. Pthirus pubis, crab louse-

mm 1 mm

FIGURE 3 FIGURE 4 FIGURE 5 Nit or egg of head louse Nit or egg of body louse Nit or egg of crab louse attached to head hair. attached to clothing attached to pubic hair. fibers.

Illustrations taken from Matheson, R., 1950, Medical Entomology, by permission of Cornell University Press, except Figure 4, from Ferns, G. F., 1951, The Suck- ing Lice, by permission of the Pacific Coast Entomological Society.

25 line. The number of lice that normally occur The head louse: Although there is no sub- on an infested person is usually a dozen or so, stantial evidence that under natural circum- but an occasional individual may harbor hun- stances head lice are vectors of human dis- dreds or even thousands of lice. ease, their status as annoying ectoparasites of man is sufficient reason to consider them A female body louse may lay 200 or more undesirable and to justify the effort to elimin- nits at a rate of 10 per day. One generation re- ate them. Head lice and their nits are usually quires on the average about 3 weeks to com- found in the hair behind the ears and on the plete. In experiments with body lice under nape but also may be found in headgear and laboratory conditions, Busvine (1948) found possibly on hair elsewhere on the body. The the nit incubation period at 30C to be 8 to incidence of head lice seems to be greater 10 days, and when held 24 hours on the host among individuals with long hair or dense the combined nymphal periods averaged 8.3 hair than in persons with short or sparse hair. days, and the adults survived for about 20 They are most frequently found on the young, days. These time periods may be prolonged the old, and the incapacitated, who are un- under natural conditions, as for example when able to groom themselves effectively. The clothing is worn intermittently. grooming behavior of the infested person in response to the irritation caused by the lice Human body lice are closely adapted to hu- is considered an important factor in keeping mans and cannot survive independently for the population of lice at a low level. long periods of time. They leave the host or the clothing voluntarily only when the host has The female head louse can lay 50 to 150 died or becomes hot with fever, or when there nits, which hatch in 5 to 10 days. The genera- is close personal contact with another host. tion time is similar to the body louse, about According to Buxton (1946) lice and their nits 3 weeks. The survival off the host and re- die when exposed to temperatures of 50C sponses to temperature extremes are also (122F) for a half hour. Both lice and nits essentially the same as that of the body have failed experimentally to survive 24 hours louse as discussed above. at -10C (l4F) or 12 hours at -l5C (5F). When off the host, all stages can be expected The diagnosis of head lice is to die within 30 days regardless of tempera- usually based upon finding the nits. The head ture. Unfed lice survive up to 10 days, the lice themselves-are less frequently seen. One length of survival time depending largely upon should be aware that foreign material or hair temperature. They are averse to direct light casts may be present which can be mistaken and frantically move to escape it when ex- for nits. For example, solidified globules of posed. It is helpful to bear these characteris- hair spray may to the casual observer, be con- tics in mind when dealing with louse problems, fused with nits. Kligman (1957), Brunner and since they represent important considerations Facq (1957), and Anderson (1958) reported in applying control measures and preventing that certain accretions on hair shafts have been the spread of infestations. mistaken for nits and offered the explanation that these nodules were probably casts from Body lice can spread .quite rapidly under un- the hair follicles. There may be several casts sanitary crowded conditions where there is on a long hair. close personal contact. During periods of so- cial upheaval when many individuals are Dr. C. Russell Anderson, dermatologist, crowded together and are unable to change (personal communication, 1971) has described clothes frequently, louse populations thrive. a hair cast as "a persistence of the inner Occasionally, however, an infestation may be hair root sheath that normally disappears at acquired under the most sanitary and uncrowd- the level of the entrance of the sebaceous ed conditions if there is close contact with in- gland duct into the hair follicle". He further fested persons or infested clothing. Under states that "these casts slide along the hair ordinary circumstances where people are able shaft with the greatest of ease, a diagnostic to change clothes frequently, the lice in point". (See Figure 6.) unworn clothes soon starve to death or are destroyed by the washing or cleaning pro- Osgood, Jellison, and Kohls (1961) re- cess, so that the infestation does not persist. ported an instance of suspected pediculosis

26 in which several thousand children were sent Head lice can be spread by the shared use home from school because it had been found of a personal item such as a hat, hairbrush, that many individuals, both children and adults, comb, or towel. They are also known to wan- had small whitish objects attached to their hair. der from an infested person onto upholstered However, only a very few actual cases of head furniture, bedding, etc. While the eradication lice were discovered. Nits can readily be dis- of a head louse infestation consists pri- tinguished from other objects upon examination marily of treating the infested person, per- under a stereoscopic microscope. sonal items likely to harbor lice should also be freed from lice.

The temporary presence of head lice is not necessarily an indication of the lack of hy- giene. An infestation might be acquired by almost anyone. Lice are able to survive sub- mersion in water for a number of hours. Bux- ton (1946) writes: "It is sometimes stated if people wash they will get rid of lice and nits. This is not the case, for soap and water at temperatures which can be tolerated do not

assure . the destruction of either. In many parts of the world there are people who are very clean in the sense that they continually wash away dirt, but they remain very lousy...."

The crab louse: There is no evidence that the crab louse is a vector of disease. However, the bites of this louse frequently cause - ing and annoyance to the infested person. The pruritus may be severe, and occasionally secondary infection results from consequent scratching. Characteristic small "blue spots" may appear in the skin tissue of the host as a result of the bites and persist for several days. These blue spots are associated only with crab louse bites and are not caused by head or body lice.

The crab louse is adapted to live in the coarser hairs of the human body, which it grasps firmly with the two pairs of enlarged claws. It is most often found on the hairs of FIGURE 6. A hair cast on a human head hair. Photomicrograph by R. E. Doty. the pubic and perianal areas. Infrequently it may occur on hairs of the other parts of the body, such as the hairs of the thigh, abdo- As in the case of body lice, head lice are men, axilla, and head as well as on the eye- activated by temperature increases. This ob- lash, eyebrow, beard, or mustache. The pres- servation might be utilized to detect their ence of crab lice on the eyelashes or head presence or to reduce their numbers on the hairs of a person does not necessarily mean host. According to Hewlett (1917): "If a comb, that the pubic area is also infested. On in- warmed enough to be pleasantly hot to the fants and young children the infestation is hand, be used, the lice become much ex- confined to the head hairs and eyelashes. cited and are as it were tempted into the open instead of sticking to their dug-outs among Like other human lice, the crab louse is the bases of the hairs. The comb thus gets found on humans almost exclusively. The very free play among them, and they are removed few exceptions have been reported from dogs. with a very marked economy of time and trou- Frye and Furman (1968) reported one instance ble." in which crab lice were found on a male dog.

27 The owner who also was infested shared his comitant with the institution of measures to bed with the dog. The authors expressed the prevent reinfestation. opinion, "The presence of a number of speci- mens on a single host seemed suggestive of more than a casual relationship between the Since the chemical treatment of louse in- dog an d lice." festations depends primarily upon products readily available on the present market, those The life history of crab lice is similar to preparations known to be available in Cali- that of head lice and body lice. Pits are atta- fornia are listed in Table 1. The reader will ched to the coarser hairs of the body and not note that no insecticidal louse powder is in- are to clothing, and they hatch in about a week. cluded in Table 1, although louse powders The three nymphal stages are passed in 2- recommended by the U.S. Public Health Serv- 2^ weeks, and the adult louse lives for about ice (1971) and the World Health Organization a month. (1970). At the time of this writing no louse powder is registered for use in California. Crab lice die in about 24 hours when sepa- rated from their human host. This and the The most common louse powders contain lethargic movements of the louse serve to in- 10% DDT, 1% lindane, or 1% deodorized mala- hibit the spread of infestations from person to thion. Their most important use is during emer- person. Although sexual contact is the most gency situations when many people must be important means of transmission, it is not the treated rapidly for body lice and when per- exclusive means. Buxton (1946) states, "There sonal appearance is a consideration second- are records of Phthirus being found on seats ary to the control of a louse-bome epidemic. of water closets and in beds, and there is While resistance to DDT and lindane has been the strong probability that they or their eggs reported for body lice in some parts of the may be spread on loose hairs dropped by in- world, no resistance has been reported for fested persons." He further notes that crab California. However, one should be alert lice can readily spread among seamen or sol- to manifestations of insecticide resistance diers living in crowded quarters. A recommen- as evidenced by the failure^o achieve satis- dation that the toilet seats in public rest rooms factory control. be raised after each use is designed to make it difficult for any stray crab louse to retain Head lice and crab lice infest the hair, and its footing, thus reducing the possibility of to eliminate the lice and their nits it usually subsequent users acquiring an infestation. is necessary to apply an insecticidal chemical to the affected areas. A liquid insecticide Apparently there has been an increase in preparation is desirable when the head hair the incidence of crab louse infestation in is treated, as a powder is unsightly and not recent years (Ackerman, 1968). These occur- very acceptable to the individual being treated. rences are not restricted to any one socio- The liquid preparations of insecticide rapidly economic group. This resurgence of crab kill all stages of the lice and are removed louse infestations is thought to be associated after a specific short time by a thorough wash with a climate of cultural permissiveness. or shower. If immediate bathing facilities are Inquiries one receives frequently betray al- inadequate or infeasible, an insecticidal most complete lack of knowledge about crab salve, lotion, or powder may be used. A louse lice, indicating the initiation of a new genera- powder may be used to treat the headgear or tion of persons poorly informed on this sub- other garments used by the infested person ject when adequate washing or cleaning is in- feasible. For the treatment of crab lice and Treatment of Human Louse Infestations their nits occurring on the eyelash, an ophthal- mic ointment containing 0.25% physostigmine The best way to control human lice is to has been recommended by Ackerman (1968) prevent them from becoming established in an and by the World Health Organization (1970). area, by seeing that the people are educated and are living in a sanitary environment. How- Except in extreme infestation with head ever, once an infestation is discovered, it is lice, it no longer is necessary to cut the hair desirable to treat the infested persons imme- prior to treatment because the modem insec- diately with an insecticidal preparation (a ticidal preparations are efficient. Unsightly pediculicide) to kill the lice and nits, con- nits remaining after the shower can be combed

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Otherwise the child is likely to be- initial treatment can be detected by inspection, come reinfested and the condition may spread thus gauging the success of the control meas- to his classmates. This situation may some- ures. times require the involvement of local health authorities, and the development of an educa- Body lice infest the clothing, particularly tional program for the affected family and com- at the seams of undergarments, so that special munity. One can refer to the Manual for the attention should be directed to control lice Control of Communicable Diseases in Cali- fornia (California and nits found in undergarments, other cloth- State Department of Public Health, for an outline of such a ing, and bedding. Laundering with hot water, 19662) louse control and a detailed or dry cleaning is enough to kill the program presentation adults, of nymphs and nits. Body lice are killed in five nursing responsibilities. minutes at 5l.5C (124.5F) and their nits are killed in 10 minutes at 52.0C (125.6F) (Buxton, 1946). With frequent changes to prop- The decision to apply a pediculicide to the erly laundered clothing, an infestation of body human body should be made thoughtfully, as a 11 lice will eventually end without treatment un- these chemicals are poisonous by definition less the person is reinfested. and can be harmful if improperly used. In their desire to rid themselves of lice, people some- Public institutions, such as hospitals and times over-react and expose themselves to prisons, occasionally may find incoming per- these chemical remedies excessively. All sons infested with lice. If the incidence is users should be advised to read and follow high, it may be necessary to apply a pediculi- precisely the directions given by the manufac- cide routinely to all admittees, but a preferable turers regarding their products. Frequency of practice is to treat only those persons found application should be restricted and appli- to have lice after inspection and diagnosis by cation to the mucous membranes and eyes is experienced health personnel. When lice are always to be avoided. found, it is desirable to treat both the infested person and the clothing no matter which louse Occasional infestations of human lice will species is involved. To disinfest the person, be found for many years to come, especially a mild insecticidal liquid preparation such as in the case of head lice and crab lice. There should be no cause for as adequate con- a shampoo containing pyrethrins is suggested. alarm, trol measures are easily available to all. How- Such an application will kill both lice and the continued presence of a louse infesta- nits within a few minutes' treatment, after ever, tion is inexcusable. As an old which the shampoo is removed by thorough saying goes, is no to have but it is to rinsing. An insecticidal powder is not suited "It disgrace lice, keep them." to this particular situation, as such a formula- tion is slow to act and must remain on the body for several days. ACKNOWLEDGMENTS If laundry and dry cleaning facilities are not available, the clothing of each individual This manuscript was reviewed by Thomas H. can be stored separately in airtight metal or Milby, M,D., Chief of the Bureau of Occupa- plastic cans or plastic bags. The proper addi- tional Health & Environmental Management, tion of an insecticide such as a louse powder and Alice Ottoboni, Ph.D., Public Health Toxi- to the container will kill nits and stray lice, cologist, both of the California State Depart- to prevent spread of the infestation or possi- ment of Public Health, 2151 Berkeley Way, ble reinfestation of the individual. An ento- Berkeley, California 94704. The manuscript mologist should be consulted if such a storage is based on an earlier article by Allan M. practice is put into operation. If the clothing Barnes and Benjamin Keh which was written must be returned immediately to the treated with the assistance of Walter Singer, Ph.D. person, it can be thoroughly dusted with a (Barnes and Keh, 1959). louse powder.

An infested school-child who returns home daily must be treated, and the familyand social 'The 1971 revision is in press.

30 REFERENCES CITED Frye, F. L., and D. P. Furman. 1968. Phthiriasis in a dog. J. Amer. Vet. Med. Assn. 152:1113. Hewlett, F. M. 1917. Notes on head- and body-lice

Ackerman, A. B. 1968. Crabs - the resurgence of and upon temperature reactions of lice and mos- Phthirus pubis. New England J. Med. 278:950- quitoes. Parasitology 10:186-188. 951. Kligman, A. M. 1957. Hair casts. Parakeratotic Anderson, C. R. 1958. Hair casts and nits. A.M.A. comedones of the scalp. A.M.A. Arch. Derma- Arch. Dermatol. 78:507. tol. 75:509-511. Barnes, A. M., and B. Keh. 1959. The biology and Mellanby, K. 1942. Natural population of the head- humanus control of lice on man. Calif. Vector Views 6:7- louse {Pediculus capitis: Anoplura) 11. on infected children in England. Parasitology 34:180-184. Blickenstaff, C. C. 1970. Common names of in- sects approved by the Entomological Society Nuttall, G. H. F. 1918. Combating lousiness among of America. 36 p. soldiers and civilians. Parasitology 10:411-586, Brunner, M. J., and J. M. Facq. 1957. A pseudo- Osgood, S. B., W. L. Jellison, and G. M. Kohls. parasite of the scalp hair. A.M.A. Arch. Derma- 1961. An episode of pseudo-pediculosis. J. Para- tol. 75:583. sitol. 47:985-986. Busvine, j. R. 1948. The 'head' and 'body' races U.S. Public Health Service, Center for Disease of Pedicitlus humanns L. Parasitology 39:1-16. Control. 1971. Public health pesticides. Pest control, vol. 39, no. 3 (25 p. article). Buxton, P. A. 1946. The louse. Second edition. The Williams and Wilkins Co.. Baltimore. 164 p. World Health Organization. 1970. Insecticide re- sistance and vector control. Seventeenth Re- California State Department of Public Health. 1966. port of the WHO Expert Committee on Insecti- A manual for the control of communicable dis- cides. WHO Technical Report Series no. 443. eases in California. 423 p. 280 p.

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