DR5.1,DR6.1 | Ectoparasitic Infestations — Glossary

An older topical scabicide (25%), effective but irritant, diluted for use in children.

The pathognomonic primary lesion of scabies — a short grey serpiginous line in the skin marking the mite's tunnel, often ending in a vesicle.

The principle that all household and close physical contacts of a scabies patient must be treated simultaneously, whether or not they are symptomatic, to prevent re-infestation.

A hyperinfestation form with thick hyperkeratotic crusts containing thousands to millions of mites, occurring in immunocompromised hosts and extremely contagious.

The dermoscopic appearance of the dark triangular head of the mite at the leading end of a burrow; a confirmatory bedside sign.

Examination of skin lesions under magnification with polarised light; used to visualise burrows and the mite in scabies.

A severe febrile rickettsial illness caused by Rickettsia prowazekii, transmitted by the body louse.

An oral antiparasitic (macrocyclic lactone) acting on invertebrate glutamate-gated chloride channels; 200 mcg/kg is first-line oral treatment for scabies.

An agent that softens and removes hyperkeratotic scale (e.g. salicylic acid), used in crusted scabies to let scabicides penetrate the thick crusts.

An older organochlorine scabicide now avoided because of neurotoxicity, particularly in children and on broken skin.

A febrile illness caused by Borrelia recurrentis, transmitted by the body louse.

Bluish-grey macules on the skin in pediculosis pubis, thought to result from louse saliva acting on blood pigment.

An organophosphate pediculicide (0.5% lotion); second-line for head lice, notably flammable and malodorous.

The egg of a louse, cemented firmly to a hair shaft or clothing fibre; nits within 1 cm of the scalp indicate active infestation.

An outdated school rule excluding children until all nits are gone; not recommended, as it causes unnecessary absence without infection-control benefit.

Infestation by lice — blood-feeding ectoparasitic insects of the order Phthiraptera.

Head-louse infestation of the scalp, caused by Pediculus humanus capitis; commonest in school-age children.

Body-louse infestation in which the louse lives in clothing seams; caused by Pediculus humanus corporis and a vector of louse-borne diseases.

Pubic-louse (crab louse) infestation of anogenital hair caused by Phthirus pubis; a sexually transmitted infestation.

The head louse; a six-legged insect spread by direct head-to-head contact.

The body louse; lives in clothing and transmits epidemic typhus, relapsing fever and trench fever.

A synthetic pyrethroid scabicide/pediculicide that disrupts invertebrate sodium channels; 5% cream is first-line topical treatment for scabies.

A synthetic pyrethroid; 1% lotion is first-line topical treatment for head and pubic lice.

The broad, crab-shaped pubic louse infesting coarse anogenital (and occasionally eyelash) hair.

Pruritus that persists for 2-4 weeks after successful killing of the mite, due to ongoing hypersensitivity; not a sign of treatment failure.

The eight-legged mite (an arachnid) that causes scabies; the fertilised female burrows into skin and lays eggs.

An intensely pruritic, contagious skin infestation caused by the mite Sarcoptes scabiei var. hominis burrowing in the stratum corneum.

Faecal pellets of the scabies mite, visible on microscopy of a skin scraping and supportive of the diagnosis.

The outermost, dead keratinised layer of the epidermis, within which the scabies mite burrows.

A traditional topical scabicide (5-10%), messy and malodorous but the safest option in neonates and pregnancy.

A febrile illness caused by Bartonella quintana, transmitted by the body louse.

Delayed, T-cell-mediated immune response; the mechanism of itch in scabies, explaining the delayed onset and post-treatment persistence of pruritus.

The chronic hyperpigmentation and lichenification of the trunk seen in long-standing pediculosis corporis.

Mechanical removal of lice and nits from damp, conditioned hair with a fine-toothed louse comb; a diagnostic and treatment adjunct.