Continuing medical education
Ectoparasites: Pediculosis and tungiasis

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Pediculosis is an infestation of lice on the body, head, or pubic region that occurs worldwide. Lice are ectoparasites of the order Phthiraptera that feed on the blood of infested hosts. Their morphotype dictates their clinical features. Body lice may transmit bacterial pathogens that cause trench fever, relapsing fever, and epidemic typhus, which are potentially life-threatening diseases that remain relevant in contemporary times. Recent data from some settings suggest that head lice may harbor pathogens. The epidemiology, clinical manifestations, and management of body, head, and pubic louse infestation are reviewed. New therapies for head lice and screening considerations for pubic lice are discussed. Tungiasis is an ectoparasitic disease caused by skin penetration by the female Tunga penetrans or, less commonly, Tunga trimamillata flea. It is endemic in Latin America, the Caribbean and sub-Saharan Africa and seen in travelers returning from these regions. Risk factors for acquiring tungiasis, associated morbidity, and potential strategies for prevention and treatment are discussed.

Section snippets

Key points

  • Body lice infestation is associated with poor hygiene or neglect

  • Given a homelessness epidemic, the diagnosis and management of body lice are essential dermatology skills

  • Body lice are vectors for potentially life-threatening pathogens

Lice are obligate parasites, feeding exclusively on the blood of infested hosts.1 Among thousands of lice species, only Pediculus humanus (P humanus) and Phthirus pubis (pubic lice) require humans as hosts. P humanus includes 2 morphotypes: P humanus corporis (body)

Key points

  • Head lice are a public health problem affecting all demographics

  • Head lice can be infected with pathogens

  • Novel US Food and Drug Administration (FDA)–approved topical therapies include benzyl alcohol 5% lotion, spinosad 0.9% suspension, and ivermectin 0.5% lotion

Head lice are ovoid-shaped, 2- to 3-mm arthropods (Fig 3, A).59, 60 Head lice are obligate human parasites that spend their entire life cycle on the scalp, feeding off blood every few hours.61 Female lice live ≤30 days and lay

Key points

  • Pubic lice infestation can involve multiple body regions

  • A diagnosis warrants screening for other sexually transmitted infections and, in children, considering the possibility of abuse

Pubic lice measure 0.8 to 1.2 mm in diameter and are wider than they are long, unlike ovoid-shaped head and body lice.60 This crab-like shape enables them to grasp widely spaced pubic hairs (Fig 4, A). Female lice lay roughly 30 eggs during their 3- to 4-week lifespan.111

Epidemiology

Pubic lice are transmitted via close

Key points

  • Tungiasis is an infestation, endemic to tropical world regions, caused by a flea burrowing into the skin

  • Tungiasis is seen in travelers returning from endemic areas

  • Tungiasis is associated with not wearing closed-toe footwear and dirt floors

Tungiasis is an ectoparasitic disease caused by skin penetration by the female Tunga penetrans or, less commonly, Tunga trimamillata flea.122 It is endemic in Latin America, the Caribbean, and sub-Saharan Africa123 and occurs in travelers returning from

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    Funding sources: None.

    Dr Chosidow has received research support from Merck Sharp & Dohme. Drs Coates, Thomas, Engelman, and Chang have no conflicts of interest to disclose.

    Date of release: March 2020

    Expiration date: March 2023

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