Arachnida: Spiders and Scorpions

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Though there are over 40,000 species of spiders and 2,000 species of scorpions worldwide, many spiders are incapable of biting humans and very few spiders and scorpions produce clinically significant bites or stings. Most spider bites and scorpion stings in humans cause minimal or no effects and rarely result in more than a local cutaneous reaction. The two spiders in the United States that are associated with potentially serious health consequences are the brown recluse (Loxosceles reclusa) and the black widow (Latrodectus mactans) spiders. Bites from the brown recluse spider can produce necrotic ulceration, while black widow spider bites can cause severe systemic features. The two scorpions in the United States causing medical relevant symptomatology are the Arizona bark scorpion (Centruroides exilcauda or sculpturatus) and striped bark scorpion (Centruroides vittatus). The Arizona bark scorpion is known to cause systemic neurotoxic symptoms and may be life-threatening, while the striped bark scorpion causes only local pain. Maintaining a broad differential diagnosis when considering a spider bite is essential due to the lack of confirmatory diagnostic testing. Scorpion stings are typically evident and also lack diagnostic testing. The treatment of spider bites and scorpion stings should include local wound care, pain management, and monitoring of systemic toxicity with a low threshold for antivenom administration. Spider bites can be prevented with the use of appropriate clothing and chemical repellents, such as N,N-diethyl-3-methylbenzamide (DEET), as well as other personal and domestic measures. Scorpion stings may be prevented through wearing appropriate protective clothing. Morbidity and mortality can be decreased through public awareness of endemic scorpion behavior and education as to when to seek medical care.