A topical review of infection-related issues

Nitpicking the Details About Lice

Jared Bullard, MD; and John M. Embil, MD, FRCPC

Very few things will give people a peculiar itchy feeling more than the mentioning of lice. is a common infestation, particularly in the pediatric population. The three species of lice ( i.e. , Pediculus humanus corporis , Pediculus humanus capitis and Phthirus pubis) account for most of the cases seen in practice; therefore, they are this month’s Bug of the Month .

What is pediculosis? of clothing and infesting other parts of the combs to hair elastics. Girls and those of body. P. pubis , which does resemble a crab, European ancestry are more likely to be Pediculosis refers to an infestation with one prefers the coarse hair typical of the groin infested. of three species of lice ( i.e. , P. humanus region but can be found in other locales, P. corporis is seen in situations of poor © ion corporis , P. humanus capitis and P. pubis ). such as body or axillary hair hor evten on the sanitation, orveirbcrowudintg and in the home - Each has a predilection for specific areas of eyebrows and eyelasheis.g less.iOsutbtreaks aaredty,pically seen in times yr D wnlo the body and causes variable amounts of p ial of wnardanod decreased personal hygiene and o rc s ca se pruritis and rash as a result of injection of C e user are spnreadl uby those with endemic lice or What is the lmife cyiscelde erso saliva and a secondary hypersensitivity om thor for p “lousy” people. ofrlicCe? d. Au opy reaction to antigens. Typically, this o ibite gle c P. pubis requires intimate contact to be ale proh a sin will occur anytime two weekSs after an usFeemale licpe rlaiynteggs either at the base of spread and could even be considered a for rised and infestation has beetn establishuedth. o viethwe hair (nits) or within the seams of cloth - sexually transmitted infection (STI). In No Una lay, disp ing. After seven to 10 days, the eggs hatch fact, one-third of people with crab lice will ll three species releasing the nymphal stage. The nymph have an additional STI. must have its first blood meal within Aof lice are 24 hours or perish. Following three molts ice can be small, flattened and two to three weeks, the nymph transmitted to becomes a mature louse, mates and the L and wingless fertilized female proceeds to lay up to anyone. arthropods of the 300 eggs over its life of 20 to 30 days. Survival off of the human host is limited to What can lice spread? Order Anoplura. 15 to 20 hours. Nits are a different matter and can remain viable upwards of a month. Aside from the association of P. pubis with All three species of lice are small, flat - STIs, lice, specifically P. corporis , can tened and wingless arthropods of the Order Who gets lice? also spread the following uncommon Anoplura. Of the more than 200 species in infections: this Order, only these three are human Lice can be transmitted to anyone. • epidemic typhus ( Rickettsia pathogens. As its name would imply, P. capitis is more common among children prowazekii ), P. capitis likes to infest the hair of the head of school age due to their close proximity • trench fever ( Bartonella quintana ) and while P. corporis can be found in the seams and tendency to share things from hats to • relapsing fever ( Borrelia recurrentis ).

18 The Canadian Journal of CME / April 2008 BUG OF THE MONTH

What are the symptoms How is pediculosis are effectively removed with a comb and of pediculosis? diagnosed? a one-to-one ratio vinegar water solution. Unlike the others, pediculosis sec - The main symptoms associated with Direct examination of the hair, body and ondary to P. corporis does not require pediculosis are related to the hypersensitiv - clothes of a suspected host for evidence of treatment. Instead, clothes and bedding ity reaction to antigens in the lice saliva. infestation is the key to diagnosis. Using a must be washed in hot water or an insec - Pruritis is the most common finding. fine-toothed or lice comb can increase the ticidal agent can be used if the item is too Erythematous papules and macules are also diagnostic yield as can a meticulous delicate. Careful ironing of seams after - common, as are excoriations from scratch - search with good lighting and a magnify - wards is important to erradicate any ing. The distribution of the rash and pruri - ing instrument. Though finding the louse residual organisms. Secondary skin infec - tis is directly related to where the lice live. itself is diagnostic, it is more likely that tions are best treated with an oral anti - In the case of P. capitis , it is typically on the nits will be discovered, usually at the base staphylococcal antibiotic. scalp, as well as the temporal and occipital of the hair shaft. Finding either a single regions of the skull. For P. corporis , expect louse or nit confirms the diagnosis. What if initial the rash to be on the trunk region. Finally, treatment fails? for P. pubis expect the main symptoms to How is pediculosis be in the groin region. Initial failures can usually be treated with treated? a course of malathion ointment, which is What are the The goals of treatment are to prevent rein - ovicidal, or by adding either ivermectin or fection and transmission and to treat the trimethoprim-sulfamethoxazole to a sec - complications of symptoms of the infestation. Antihistamines ond round of . This will pediculosis? are useful to treat the pruritis as are topical increase the treatment efficacy to 95%. By far, the most common complication is corticosteroids. Less popular alternatives include head a secondary skin infection. Skin organ - Elimination of the lice is achieved by shaving, shower caps and petroleum jelly isms, particularly Staphylococcus aureus , a variety of agents including 1% and manual removal. like to take up residence in excoriated creams, 1% permethrin and malathion skin. Occasionally, with cases of pedicu - lotions. The treatment of choice is How do you prevent the losis due to P. corporis , the skin may pyrethrum agents, an extract of the become hyperpigmented and markedly chrysanthemum. Malathion and perme - spread of lice? thickened. Together, these findings are thrin are both “Pregnancy Category B” Improved living conditions and personal called Vagabond’s disease. drugs, meaning that although good stud - sanitation are both helpful as is the avoid - ies are absent to confirm safety in ance of sharing of fomites, such as combs humans, the agents are presumed safe due and brushes. The “no nit” policies of Dr. Bullard is a Fellow in Pediatric to an absence of reported adverse effects many schools have not proven efficacious Infectious Diseases and Medical Microbiology, University of Manitoba, despite wide scale use in pregnancy. for the prevention of spread, thus children Winnipeg, Manitoba. Breastfeeding safety is unknown. should not miss school on account of Lindane is often avoided in pregnancy louse eggs. Dr. Embil is a Consultant, Infectious due to its potential neurotoxicity. A brief Diseases and an Associate Professor, University of Manitoba. 10 minute application to affected areas of He is also the Medical Director, permethrin is adequate to kill 70% to Infection Prevention and Control Program, Health Sciences Centre 80% of the nymphs and adult lice; and Winnipeg Regional Health however, this agent is not ovicidal so a Authority, Winnipeg, Manitoba. repeat is necessary in one week time. Nits

The Canadian Journal of CME / April 2008 19