The pain may be intense enough to mimic myocardial infarction or acute abdomen, but it is rarely life threatening and typically resolves within 48 to 72 hours. After a person has been bitten, crampy muscle spasms usually occur within an hour in the chest (upper extremity bites) or the abdomen (lower extremity bites). Widow venom contains α-latrotoxin, which provokes a massive presynaptic release of acetylcholine. Widow spiders typically reside in yard debris, and their bite, which feels like a pinprick, is associated with recent outdoor activity. Introduced brown widow spiders ( Latrodectus geometricus) are found in the South, and have an orange or yellow hourglass mark and milder venom. mactans is black, usually with a classic red hourglass mark on the ventral abdomen ( Figure 1). mactans in the East, Latrodectus hesperus in the West, and Latrodectus variolus in the North. Of the five species in the United States, the three most common are L. Applying insect repellent containing diethyltoluamide (DEET) 10% to 35% or picaridin 20% is the best method for preventing bites. Antihistamines are usually the only treatment required for insect bites however, severe mosquito reactions (skeeter syndrome) may require prednisone. Flea bites are usually on ankles, whereas mosquito bites are on exposed skin, and chigger bites tend to be along the sock and belt lines. Bites from fleas, bedbugs, biting flies, and mosquitoes present as nonspecific pruritic pink papules, but the history and location of the bite can assist with diagnosis. The prophylactic use of a single dose of doxycycline for Lyme disease may be justified in high-risk areas of the country when an attached, engorged black-legged tick is removed. ![]() Ticks of medical importance in the United States include the black-legged tick, the Lone Star tick, and the American dog tick. Treatment of clothing with permethrin and proper tick removal greatly reduce the risk of infection. Tick bites can transmit diseases only after prolonged attachment to the host. Most recluse bites resolve uneventfully without aggressive therapy and require only wound care and minor debridement. ![]() Widow bites usually respond to narcotics, benzodiazepines, or, when necessary, antivenom. The two medically important spiders in the United States are widow spiders (Latrodectus), the bite of which causes intense muscle spasms, and the brown recluse (Loxosceles), which may cause skin necrosis. ![]() Although their bites typically cause only local reactions, some species are venomous or transmit disease. The phylum Arthropoda includes arachnids and insects.
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