The order Lepidoptera includes butterflies and moths and their caterpillars. Symptoms that result from contact with this class of insects are referred to as lepidopterism. Caterpillars have hair or spines for protection, which are also sometimes connected to a venom gland. Contact with these spines usually causes localized skin irritation and pruritus. Megalopyge opercularis, also known as the “puss caterpillar,” is mainly found in the southeastern United States and accounts for the majority of envenomation cases in this country. Intense local burning pain is typical at the site of contact and is followed by a grid-like pattern of hemorrhagic papules, which appear 2 to 3 hours after exposure and may last for several days. Regional lymphadenopathy is common. Other symptoms include headache, fever, hypotension, and convulsions. No deaths have ever been reported.
As there is no antivenin available for lepidopterism, treatment is mostly supportive. If spines are visible following contact, they should be removed with adhesive tape. Antihistamines and steroids may be used for symptom control. In patients with hypotension, IV fluids and IV epinephrine may be required.43
Coleoptera
The order Coleoptera includes a large number of beetles, though clinically significant envenomation occurs only with blister beetles. There are over 1,500 species of blister beetles worldwide, approximately 2,002 of which are in the United States. The blister beetle responsible for most of the medically significant envenomations is Cantharis vesicatoria—also known as “Spanish fly.” Of note, the Spanish fly is not naturally found in the United States.
Cantharidin-containing substances are sometimes used medicinally in wart removal preparations and are also sold for their purported aphrodisiac effects (the associated vascular congestion and urethral inflammation are interpreted as enhanced sexuality). Transdermal absorption or ingestion may lead to systemic toxicity with severe vomiting, hematemesis, abdominal pain, diarrhea, hematuria, renal failure, etc. Death has been reported after large ingestions.
Treatment is largely supportive. The skin should be irrigated thoroughly after exposure, followed by local wound care. Patients who present after ingestion should be admitted to the hospital for further treatment and care.47
Conclusion
Knowledge of a vast array of stinging insects and spiders is important for any clinician, but the appropriate evaluation and treatment of bites and envenomations are crucial for EPs. Most exposures can be treated with supportive care, while others require in-depth knowledge and clinical expertise.
Dr Deljoui is a former resident, department of emergency medicine, Eastern Virginia Medical School, Norfolk; and current critical care fellow, University of Maryland, Baltimore.
Dr Knapp is an associate professor and residency program director, department of emergency medicine, Eastern Virginia Medical School, Norfolk.