Ectoparasitic Infections

Pediculosis Pubis

Persons who have pediculosis pubis (i.e., pubic lice) usually seek medical attention because of pruritus or because they notice lice or nits on their pubic hair. Pediculosis pubis is usually transmitted by sexual contact (849).

Treatment

Reported resistance to pediculcides (permethrin and pyrethrins) has been increasing and is widespread (850,851). Malathion can be used when treatment failure is believed to have occurred as a result of resistance. The odor and long duration of application associated with malathion therapy make it a less attractive alternative compared with the recommended pediculcides. Ivermectin has limited ovicidal activity (852). Ivermectin might not prevent recurrences from eggs at the time of treatment, and therefore treatment should be repeated in 14 days (853,854). Ivermectin should be taken with food because bioavailability is increased, in turn increasing penetration of the drug into the epidermis. Adjustment of ivermectin dosage is not required for persons with renal impairment, but the safety of multiple doses in persons with severe liver disease is not known.

Lindane is recommended as an alternative therapy because it can cause toxicity, as indicated by seizure and aplastic anemia (855); it should only be used when other therapies cannot be tolerated or have failed. Lindane toxicity has not been reported when treatment was limited to the recommended 4-minute period. Lindane should not be used immediately after a bath or shower, and it should not be used by persons who have extensive dermatitis, women who are breastfeeding, or children aged <10 years (855).

Other Management Considerations

The recommended regimens should not be applied to the eyes. Pediculosis of the eyelashes should be treated by applying occlusive ophthalmic ointment or petroleum jelly to the eyelid margins twice a day for 10 days. Bedding and clothing should be decontaminated (i.e., machine-washed and dried using the heat cycle or dry cleaned) or removed from body contact for at least 72 hours. Fumigation of living areas is not necessary. Persons with pediculosis pubis should be evaluated for other STDs, including HIV.

Follow-Up

Evaluation should be performed after 1 week if symptoms persist. Re-treatment might be necessary if lice are found or if eggs are observed at the hair-skin junction. If no clinical response is achieved to one of the recommended regimens, retreatment with an alternative regimen is recommended.

Management of Sex Partners

Sex partners within the previous month should be treated. Sexual contact should be avoided until patients and partners have been treated, bedding and clothing decontaminated, and reevaluation performed to rule out persistent infection.

Special Considerations

Pregnancy

Existing data from human subjects suggest that pregnant and lactating women should be treated with either permethrin or pyrethrins with piperonyl butoxide. Because no teratogenicity or toxicity attributable to ivermectin has been observed in human pregnancy experience, ivermectin is classified as “human data suggest low risk” in pregnancy and probably compatible with breastfeeding (317). Use of lindane during pregnancy has been associated with neural tube defects and mental retardation, and it can accumulate in the placenta and in breast milk (855).

HIV Infection

Persons who have pediculosis pubis and also HIV infection should receive the same treatment regimen as those who are HIV negative. For more information, see Pediculosis pubis.

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Scabies

The predominant symptom of scabies is pruritus. Sensitization to Sarcoptes scabiei occurs before pruritus begins. The first time a person is infested with S. scabiei, sensitization takes up to several weeks to develop. However, pruritus might occur within 24 hours after a subsequent reinfestation. Scabies in adults frequently is sexually acquired, although scabies in children usually is not (856,857).

Treatment

Permethrin is effective, safe, and less expensive than ivermectin (858). One study demonstrated increased mortality among elderly, debilitated persons who received ivermectin, but this observation has not been confirmed in subsequent reports (859). Ivermectin has limited ovicidal activity and may not prevent recurrences of eggs at the time of treatment; therefore, a second dose of ivermectin should be administered 14 days after the first dose. Ivermectin should be taken with food because bioavailability is increased, thereby increasing penetration of the drug into the epidermis. Adjustments to ivermectin dosing are not required in patients with renal impairment, but the safety of multiple doses in patients with severe liver disease is not known.

Lindane is an alternative regimen because it can cause toxicity (855); it should only be used if the patient cannot tolerate the recommended therapies or if these therapies have failed (860-862). Lindane should not be used immediately after a bath or shower, and it should not be used by persons who have extensive dermatitis or children aged <10 years. Seizures have occurred when lindane was applied after a bath or used by patients who had extensive dermatitis. Aplastic anemia after lindane use also has been reported. Lindane resistance has been reported in some areas of the world, including parts of the United States.

Other Management Considerations

Bedding and clothing should be decontaminated (i.e., either machine-washed, machine-dried using the hot cycle, or dry cleaned) or removed from body contact for at least 72 hours. Fumigation of living areas is unnecessary. Persons with scabies should be advised to keep fingernails closely trimmed to reduce injury from excessive scratching.

Crusted Scabies

Crusted scabies (i.e., Norwegian scabies) is an aggressive infestation that usually occurs in immunodeficient, debilitated, or malnourished persons, including persons receiving systemic or potent topical glucocorticoids, organ transplant recipients, persons with HIV infection or human T-lymphotrophic virus-1-infection, and persons with hematologic malignancies. Crusted scabies is transmitted more easily than scabies (863). No controlled therapeutic studies for crusted scabies have been conducted, and the appropriate treatment remains unclear. Substantial treatment failure might occur with a single-dose topical scabicide or with oral ivermectin treatment. Combination treatment is recommended with a topical scabicide, either 25% topical benzyl benzoate or 5% topical permethrin cream (full-body application to be repeated daily for 7 days then 2x weekly until discharge or cure), and treatment with oral ivermectin 200 ug/kg on days 1,2,8,9, and 15. Additional ivermectin treatment on days 22 and 29 might be required for severe cases (864). Lindane should be avoided because of the risks for neurotoxicity with heavy applications or denuded skin.

Follow-Up

The rash and pruritus of scabies might persist for up to 2 weeks after treatment. Symptoms or signs persisting for >2 weeks can be attributed to several factors. Treatment failure can occur as a result of resistance to medication or faulty application of topical scabicides. These medications do not easily penetrate into thick, scaly skin of persons with crusted scabies, perpetuating the harboring of mites in these difficult-to-penetrate layers. In the absence of appropriate contact treatment and decontamination of bedding and clothing, persisting symptoms can be attributed to reinfection by family members or fomites. Finally, other household mites can cause symptoms to persist as a result of cross reactivity between antigens. Even when treatment is successful, reinfection is avoided, and cross reactivity does not occur, symptoms can persist or worsen as a result of allergic dermatitis.

Retreatment 2 weeks after the initial treatment regimen can be considered for those persons who are still symptomatic or when live mites are observed. Use of an alternative regimen is recommended for those persons who do not respond initially to the recommended treatment.

Management of Sex Partners and Household Contacts

Persons who have had sexual, close personal, or household contact with the patient within the month preceding scabies infestation should be examined. Those found to be infested should be provided treatment.

Management of Outbreaks in Communities, Nursing Homes, and Other Institutional Settings

Scabies epidemics frequently occur in nursing homes, hospitals, residential facilities, and other communities (865). Control of an epidemic can only be achieved by treating the entire population at risk. Ivermectin can be considered in these settings, especially if treatment with topical scabicides fails. Epidemics should be managed in consultation with a specialist.

Special Considerations

Infants, Young Children, and Pregnant or Lactating Women

Infants and young children should be treated with permethrin; the safety of ivermectin in children who weigh <15 kg has not been determined. Infants and young children aged<10 years should not be treated with lindane. Ivermectin likely poses a low risk to pregnant women and is likely compatible with breastfeeding (See Pediculosis pubis); however, because of limited data regarding its use in pregnant and lactating women, permethrin is the preferred treatment (317).

HIV Infection

Persons with HIV infection who have uncomplicated scabies should receive the same treatment regimens as those who are HIV negative. Persons with HIV infection and others who are immunosuppressed are at increased risk for crusted scabies. Such persons should be managed in consultation with a specialist.

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