Venomous bites and stings

A 32-year-old man presented to the ED after being bitten on the hand by a small black spider with a red hourglass marking during a hike in southeastern South Carolina. What began as a mild sting quickly escalated: within an hour, the patient developed severe muscle cramps, abdominal discomfort, diaphoresis, and palpitations. Fortunately, the patient captured a photo of the spider, which aided in its identification (Figure 1).FIGURE 1.: Female black widow (L. mactans). Source: CDC.GENERAL FEATURES Arthropod bites and stings usually cause minor, self-limited reactions. The two medically relevant spiders in the United States are the southern black widow (Latrodectus mactans) and the brown recluse spider (Loxosceles reclusa). Hymenoptera (a large order of insects including bees, wasps, hornets, and fire ants) account for the highest number of arthropod-related deaths in humans, most commonly due to severe allergic reactions. Medically important scorpions are generally limited to the genus Centruroides in the United States. The United States has two major groups of medically important venomous snakes: the family Elapidae (coral snakes) and the Viperidae subfamily Crotalinae (pit vipers, including rattlesnakes, water moccasins, and copperheads).1 CLINICAL ASSESSMENT Spider bites Southern black widow (L. mactans) Bites are often felt as a pinprick or mild sting. Symptoms typically begin 30 to 60 minutes after the bite. Presentation is characterized by rapid-onset severe muscle cramping, abdominal rigidity, diaphoresis, hypertension, tachycardia, and localized erythema (usually without blistering). Additional manifestations may include vomiting, seizures, and, in severe cases, shock. Brown recluse (L. reclusa) Symptom onset is delayed, with pain and pruritus developing 2 to 8 hours after the bite. A blister is commonly the initial lesion, which may evolve into an ulcer with surrounding erythema and tissue necrosis. Systemic symptoms (loxoscelism) may include fever, hemolysis, renal failure, and muscle cramping. Hymenoptera stings (bees, wasps, hornets, fire ants) Local reactions include pain, erythema, and swelling. Systemic reactions entail anaphylaxis, urticaria, hypotension, bronchospasm, and angioedema. Scorpion stings (mainly Centruroides species) Present with immediate localized pain, paresthesia, and sometimes fasciculations. Severe envenomation—more common in children—may cause neuromuscular toxicity, cranial nerve dysfunction, and respiratory compromise. Snakebites (Crotalinae: rattlesnakes, water moccasins, copperheads) Bites typically present with two puncture wounds at the bite site, followed by localized pain, swelling, and ecchymosis. Hemorrhagic bullae may develop. Systemic effects may include hypotension, coagulopathy, myokymia (often in the upper extremities or near the bite site), and altered mental status. Box 1DIAGNOSIS Spider bites: Diagnosed based on patient history and symptom progression. Brown recluse bites may require wound cultures if secondary infection is suspected. Hymenoptera stings: Diagnosed based on patient history—particularly multiple stings or systemic allergic reactions. Measuring serum tryptase levels may be helpful when anaphylaxis is suspected. Scorpion stings: Diagnosed based on regional prevalence and neurological symptoms. Snakebites: Diagnosed based on patient history. Ask patients about the snake's appearance to help identify the species and guide treatment. Patients and bystanders should not attempt to capture or kill the snake for the sake of identifying it, as this is dangerous and can result in additional bites. Obtain coagulation studies, complete blood cell count, and electrolyte panels. TREATMENT Spider bites Southern black widow Mild cases: Clean the bite area with soap and water, offer oral analgesics (acetaminophen or ibuprofen), and monitor for worsening symptoms. Moderate to severe cases: Administer opioids (eg, morphine) for pain relief, benzodiazepines (eg, lorazepam) for muscle spasms, and consider antivenom if symptoms persist. Brown recluse Clean the wound with soap and water immediately. Apply cold packs and use nonsteroidal anti-inflammatory drugs (NSAIDs) or opioids as needed for pain control. Debridement may be necessary for significant tissue necrosis. Ensure tetanus prophylaxis is up to date (administer booster if more than 5 years have passed since the last dose). Hymenoptera stings Localized reactions: Wash the area with soap and water, remove any rings or constrictive items, and apply cold compresses. Antihistamines and NSAIDs can help reduce swelling and discomfort. Anaphylactic reactions: Promptly administer intramuscular epinephrine. Follow with antihistamines, corticosteroids, intravenous fluids, and airway management as needed. Scorpion stings Focus on supportive care and pain relief as first-line management. Specific antivenom is indicated for severe envenomation with neuromuscular dysfunction, cranial nerve abnormalities, or cardiovascular compromise. Monitor closely for any signs of respiratory distress. Snakebites Immobilize the affected limb at heart level to limit venom spread. Administer antivenom (eg, CroFab for all Crotalinae envenomations; ANAVIP is an alternative for rattlesnake and copperhead envenomations) if progressive symptoms, coagulopathy, and/or systemic toxicity are observed. Provide supportive care with intravenous fluids and pain management (avoid NSAIDs due to bleeding risk). Ensure tetanus prophylaxis is up to date. Avoid tourniquets, wound incision, caffeine, alcohol, and attempts at venom suction. CASE RESOLUTION This case illustrates a classic, rapid-onset presentation of black widow envenomation, marked by severe muscle cramping, autonomic instability, and abdominal rigidity. Early recognition and prompt management, utilizing benzodiazepines for muscle spasms, intravenous fluids for supportive care, and antivenom in severe cases, are essential to minimize complications and optimize patient outcomes.Box 2