Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

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Section V: Environmental Medicine

Adult ticks are eight-legged arthropods ranging in size from nearly microscopic to a centimeter in diameter. The ticks of greatest concern, for Lyme disease at least, are two to four millimeters in diameter, and before they begin to feed are not easily recognized as a foreign creature on your skin.

as filariasis, have no definitive cure and no effec- tive prophylactic medication. The fewer mosqui- toes you feed, the less your chance of becoming ill.

Mosquito-borne Disease

General Principles

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Prevention: • DEET, Picaridin, IR3535 or Lemon/Eucalyptus** on skin • Permethrin on clothing • Tight weave clothing • Avoid feeding time • Pre or post exposure prophylaxis in Malaria endemic regions*

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* See www.cdc.gov ** not against malaria

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The same clothing and repellent tactics used with ticks apply well here. In addition, avoid being exposed during the times of day when vec- tor mosquitoes feed. This is typically dawn and dusk but may be a few hours during the middle of the night depending on location. Permethrin- impregnated bed nets have been very successful in some places, but some mosquito populations have changed their feeding time behavior, possibly in response to the nighttime use of bed nets. Local knowledge may help with your prevention plan. Fleas, Lice, and Mites Sometimes the adult insect is easily seen, such as lice in the hairline or a flea in your bedding. More 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

Lyme disease rash Once attached and engorged with blood, ticks lookmore like a wart, mole, or other skin part, and may be missed by someone who does not know your body as well as you do. The appearance of flu- like symptoms, severe headaches, fever, rash, and muscular aches and pains several days to weeks after a confirmed long-term tick attachment or travel in a tick-infested area is worth immediate medical evaluation for several tick-borne illnesses. Mosquitoes The list of diseases transmitted by mosquitoes includes malaria, filariasis, West Nile virus, equine encephalitis, dengue fever, and a host of others. The key to avoiding these infections is to avoid being a host to mosquitoes. Like ticks, they can be deterred by insect repellent and tight-weave clothing. Unlike ticks, they can transmit disease in less than a minute. Prophylactic medication with atovaquone/pro- guanil, doxycycline or others can help prevent malaria infection. However, some diseases, such