Scabiespoints to note

• There may be very few burrows, though the patient has widespread itching

• The distribution of the infestation is characteristically the fingers, wrists, nipples, abdomen, genitalia, buttocks, and ankles

• Close personal contact is required for infestation to occur, for example, within a family, through infants in playgroups, and through regular nursing of elderly patients

• Itching may persist even after all mites have been eliminated; itching papules on the scrotum and penis are particularly persistent

Larva migrans

Burrows of scabies

Gnathostomiasis Fotos

Larva migrans

Treatment

This is either by freezing the advancing end of the lesion with liquid nitrogen or by applying thiabendazole (10%) suspension. Similar lesions in patients returning from tropical countries raise the possibility of larva migrans from strongyloides infestation, myiasis from the larvae of flies, or gnathostomiasis.

Visceral larva migrans caused by Toxocara canis and Ascaris lumbricoides may produce a transient rash.

Pediculosts (lice)

Infestation with lice became less common in the postwar years, but the incidence has recently increased.

There are three areas of the body usually affected by two species of wingless insects—Pediculus humanus, infecting the head and body, and Phthirus pubis, the pubic louse. The wingless insects feed on blood aspirated at the site of the bite, and each female lays 60-80 encapsulated eggs attached to hairs—"nits" in common parlance.

Head lice are transmitted via combs, brushes, and hats, being more common in girls than boys. The infestation is heaviest behind the ears and over the occiput. If the eyelashes of children are affected this is with "crab lice" (Phthlrus pubis); it is not pediculosis.

Body lice are less common in western Europe. Transmission is by clothing and bedding, on which both lice and their eggs may be found in the seams. Poor hygiene favours infestation.

Pubic lice infestation occurs worldwide and is generally transmitted by sexual contact. Infestation of eyelashes may occur with poor hygiene.

As a result of scratching there may be marked secondary infection that obscures the underlying infestation.

Treatment

Gamma benzene hexachloride 1% is usually effective as a single application. Permethrin can also be used.

Pediculosis capitis

Phthirus pubis on eyelashes

Further reading

Alexander JO. Arthropods and human skin. Berlin: Springer-Verlag, 1984

Busvine JR. Insects and hygiene, 3rd ed. London: Chapman and Hall, 1980

Marshall AG. The ecology of ectoparasitic insects. New York: Academic Press, 1981

Parish CL, Nutting WB, Schwartzman RM. Cutaneous infestation of man and animal. New York: Greenwood, 1983

Pediculosis capitis

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