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

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Section V: Environmental Medicine

after being in a likely habitat should raise the sus- picion of a black widow bite. Treatment includes evacuation to medical care if your patient shows signs of critical system involvement or needs medication to reduce muscle spasm. Antivenin is available but may carry more risk than the venom itself. Symptoms usually resolve over several days but may persist for weeks. Despite its ominous name, death from the bite of a black widow is extremely rare in North America. Brown Recluse The brown recluse is a large spider found in the south-central United States that injects a long-acting tissue toxin causing localized tissue inflammation and necrosis. The initial bite may go unnoticed, with a pustule developing several days later. This is often mistaken for an infec- tion caused by a splinter or other foreign body. It does not respond to incision and drainage or to antibiotics.

bothersome in North America is the bark scor- pion (Centruroidies sp.), which employs a potent neurotoxin. Pain may last for hours or days. There is no specific field treatment beyond pain medication. Ice is not indicated. Significant sys- temic symptoms are rare and include agitation and respiratory paralysis; these should prompt an evacuation to medical care. An antivenin is available, but it is a high-risk treatment owing to the incidence of serum sickness and anaphy- laxis. No fatalities fromCentruroidies stings have been reported in the United States, and very rarely elsewhere.

Arizona Bark Scorpion under blacklight

Tick Paralysis The saliva of some species of ticks contains a neu- rotoxin capable of causing symptoms in humans, most commonly in children. Tick paralysis can develop after 4 or more days of attachment and is characterized by numbness and paralysis pro- gressing up the legs and arms. The patient may exhibit ataxia (stumbling gait), restlessness, or irritability. The diagnosis is suspected by find- ing an engorged tick and confirmed by rapid improvement following its removal. Tick paralysis is rare but can cause fatal respira- tory paralysis if the tick is not found and removed. Ticks are more commonly implicated as vectors of bacterial and parasitic disease. Prevention of tick paralysis and tick-borne disease depends on avoiding bites and early removal of attached ticks.

Brown recluse (Loxosceles reclusa) Although many of these envenomations resolve uneventfully, the lesion can continue to progress over days and weeks to involve a large area of tissue destruction that may become secondarily infected. A suspected brown recluse bite should be referred to a surgeon. Many lesions believed to be caused by a brown recluse turn out to be other problems. Centruroidies Most scorpion stings are described as similar to, or a bit worse than, your average wasp. Most