The order Scorpionida contains several families, genera, and species of scorpions. All have paired venom glands in a bulbous segment, called the telson, that is situated just anterior to a stinger on the end of the six terminal segments of the abdomen (often called a tail). The only systemically poisonous species in the United States is Centruroides exilicauda (formerly C sculpturatus), also known as the bark scorpion. The most serious envenomations usually are reported in children younger than 10 years of age. This scorpion is found primarily in the arid southwestern United States but has been found as a stowaway in cargo as far north as Michigan. Other dangerous scorpions are found in Mexico (Centruroides species), Brazil (Tityus species), India (Buthus species), the Middle East, and North Africa and the eastern Mediterranean (Leiurus and Androctonus species).
The scorpion grasps its prey with its anterior pincers, arches its pseudoabdomen, and stabs with the stinger. Stings also result from stepping on the stinger. The venom of C exilicauda contains numerous digestive enzymes (eg, hyaluronidase and phospholipase) and several neurotoxins. These neurotoxins can cause alterations in sodium channel flow, resulting in excessive stimulation at neuromuscular junctions and the autonomic nervous system.
Variable amounts of venom, from none to the complete contents of the telson, may be ejected through the stinger.
Common scorpion stings. Most stings result only in local, immediate burning pain. Some local tissue inflammation and occasionally local paresthesias may occur. Symptoms usually resolve within several hours. This is the typical scorpion sting most often seen in the United States.
Dangerous scorpion stings. In some victims, especially children younger than 10 years, systemic symptoms can occur after stings by Centruroides species, including weakness, restlessness, diaphoresis, diplopia, nystagmus, roving eye movements, hyperexcitability, muscle fasciculations, opisthotonus, priapism, salivation, slurred speech, hypertension, tachycardia, and rarely convulsions, paralysis, and respiratory arrest. Envenomations by Tityus, Buthus, Androctonus, and Leiurus species have caused pulmonary edema, cardiovascular collapse, and death, as well as coagulopathies, disseminated intravascular coagulation, pancreatitis, and renal failure with hemoglobinuria and jaundice. In nonfatal cases, recovery usually occurs within 12–36 hours.
The scorpion must have been seen by the patient or the clinician must recognize the symptoms. There is no readily available laboratory test to confirm scorpion envenomation. In the case of Centruroides stings, tapping on the sting site usually produces severe pain ("tap test").
Specific levels. Body fluid toxin levels are not available.
No other useful laboratory studies are needed for minor envenomations. For severe envenomations, obtain CBC, electrolytes, glucose, BUN, creatinine, and coagulation profile. In small children with severe symptoms, oximetry can be used to aid recognition of respiratory insufficiency.