Scorpions are members of the arthropod phylum, which includes insects, spiders, crustaceans, and other similar creatures that have segmented bodies with appendages on each segment. There are over 1200 species of scorpions found on all continents except Antarctica, and they vary in size from a few millimeters to 15 centimeters. Scorpions are active at night and hide during the day, and most species are heat tolerant.
The segmented "tail" of a scorpion ends in a vesicle that stores venom and a sting. Muscular action squeezes venom through twin openings at the base of the sting, and then the venom travels through the sting to its tip. When provoked, the scorpion uses the sting to pierce the skin of its victim and inject the venom. The size of the scorpion does not correlate with the potency of venom.
Scorpion venom is quite variable from species to species but primarily contains neurotoxins. The neurotoxins block ion channels, particularly sodium and potassium, causing pain and paresthesias. Secondary systemic effects are caused by massive release of acetylcholine and catecholamines. The venoms generally lack locally active toxins to produce tissue destruction.
Scorpion envenomations are responsible for more deaths than any other venomous arthropods. Worldwide, approximately 5000 people die annually from scorpion stings, most stung by one of approximately 30 dangerous scorpion species. Serious envenomations typically affect the young, old, and infirm. Most people die from excessive stimulation of the sympathetic nervous system resulting in respiratory, cardiovascular, and central nervous system failure. Anaphylaxis is rare.
Envenomation from a scorpion sting initially causes significant pain at the puncture site, and the pain can increase markedly with tapping lightly over the wound. Local pain and paresthesias can extend proximally along the limb for several hours and then will gradually retreat. Pain at the sting site, hyperesthesias, and hot-cold reversal can last for months. There will be little to no local inflammation at the sting site.
With systemic envenomation, transient release of excessive acetylcholine can cause salivation, lacrimation, urination, defecation, gastric distress, emesis and bronchorrhea ("SLUDGE" syndrome), and muscle contraction. Subsequently, excessive norepinephrine is released and can cause significant hypertension, tachycardia, hyperthermia, diaphoresis, and myocardial depression. End organ damage such as pulmonary edema, myocardial infarction without thrombosis, hyperglycemia, pancreatitis, and ischemic stroke may occur with severe envenomation. When the central nervous system is involved, the patient may be confused, agitated, ataxic, and have myoclonic or dystonic movements. Systemic symptoms present in the initial 6 hours after envenomation and last up to 12 hours. Tachycardia may persist up to 2 weeks.
It is important to know where the dangerous scorpion species live.
Centruroides species are found in the southwestern United States, Mexico, and Central America. In Mexico, for every person killed by a venomous snake, the Centruroides scorpion kills 10. Centruroides exilicauda, the Arizona bark scorpion,found in the southwestern United States and northern Mexico, can inflict a very painful sting. In children, severe involuntary motor activity, agitation, and respiratory difficulties can occur. No deaths have been reported for this species in the United States since 1968 (excluding deaths due to anaphylaxis).
Tityus species are found in Central America, South America, and the West Indies. Systemic envenomation from Tityus trinitatis (the devil scorpion) causes pancreatitis in 80% of victims.
Mesobuthus species are found in India. Envenomation from an Mesobuthus tamulus (red scorpion) sting hada30% fatality rate in a study done in the 1960s-1970s, but now only a 2%-3% fatality rate with prompt treatment using vasodilators and calcium-channel blockers.
Buthus species of the Mediterranean, Leiurus species (eg, death stalker) of North Africa and the Middle East, and Androctonus species (eg, fat-tailed scorpion) of North Africa and Southeast Asia are other dangerous scorpion species.
ICD10CM: T63.2X1A – Toxic effect of venom of scorpion, accidental, initial encounter
SNOMEDCT: 217670007 – Poisoning due to scorpion venom