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11.19 Pediculosis (Lice, crabs)


Presentation

Patients arrive with emotions ranging from annoyance to sheer disgust at the discovery of an infestation with lice or crabs and request acute medical care. There may be extreme pruritis and the patient may bring in a sample of the creature to show you. The adult forms of head lice (pediculosis) can be very difficult to find but their oval, light gray eggs (nits) can be readily found firmly attached to the hairs above the ears and toward the occiput. Secondary impetigo and furunculosis can occur. The adult forms of pubic lice (pthirus or crab lice) are more easily found, but their light yellow gray color still makes them difficult to see. Small black dots present in infested areas represent either ingested blood in adult lice or their excreta.

What to do:

What not to do:

Discussion

Head and pubic lice are obligatory bloodsucking ectoparasites whose eggs are firmly attached to the hair shafts near the skin, and incubate for about a week before hatching. Nits located more than one-half inch from the scalp are no longer viable.

A common alternate treatment for lice is lindane shampoo which is only available by prescription. One ounce is worked into the affected area for four minutes and then thoroughly rinsed out. Because of the very toxic nature of lindane, its use should be reserved for those cases that fail to respond to pyrethrins (RID). Treatment with either substance may not be ovicidal and therefore re-treatment after 7 to 10 days is often recommended.


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from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
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Craig Feied, MD
Mark Smith, MD
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