Wilderness and Rescue Medicine 8th Edition

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Section V: Environmental Medicine

often, the infestation is suspected by the sudden appearance of itchy bites following a night in a strange bed or interaction with a pet. A careful inspection of hair, bedding, or clothing will usu- ally identify the offending organism. Only about 5% of a given flea population is actively feeding on blood. The rest are at various stages of development as eggs, pupae, and larvae. Adult fleas can hibernate for up to 2 years waiting for a blood meal. The worst place to sleep is on that old mattress in the trekking hut that was last occupied 6 weeks ago.The eggs, pupae, and larvae have matured and are waiting for you. Only a few of them need to be carrying the bacteria Yersinia pestis to give you bubonic plague. Fleas can be killed or deterred by insect repellents and insecticides. Your own sleep- ing bag, frequently washed, is another good defense.

Nit of a louse on a hair Mites can be a bit more difficult to identify and treat. Most are too small for the naked eye to see and can cause a variety of rashes. Most mite infes- tations are self-limiting because the human is not the normal host. The mite may feed temporarily and drop off without burrowing or reproducing. The rash disappears when contact with the host organism is discontinued. The most common and troubling mite infesta- tion is scabies (Sarcoptes scabiei). Humans are the normal host where the mite enjoys a full life cycle in the outer layers of the skin. Scabies is usually passed between people by skin-to-skin contact. The symptoms begin with a few small and intensely itchy red spots that slowly spread over days or weeks to involve other body areas, especially where the host human can scratch and spread eggs from one site to another. Epidemics within close groups or families is common. A host can begin to spread scabies before symptoms become apparent. Secondary bacterial infection is an anticipated problem. Treating scabies requires application of 5% per- methrin cream or other topical scabicide that is left on the skin for several hours. Bedding and clothing can be treated with a hot dryer. Preferably the patient, clothing, and bedding are treated simultaneously to prevent repeat infestation.

Human louse Lice are easily transmitted between people shar- ing clothing and furniture.They tend to limit their range to groin or head hair. The adults are easily killedwith permethrin or malathion. Reapplication may be necessary in 10 days to kill the newly hatched larvae. In the absence of permethrin sham- poo, lice can also be smothered with a layer of any viscous substance such as Vaseline or mayonnaise. It may not be pretty, but it can solve your problem.