Creature Discomforts 2: A Quiz

While he was doing yard work, a man experienced acute, severe, burning pain. The lesion shown in the photograph developed subsequently. The patient had paresthesias for nearly a week after the incident.

Which of the organisms pictured here is the most likely culprit?

Answer: C

Photo C shows the "asp" (puss) caterpillar, Megalopyge opercularis. This organism is found along the Eastern seaboard and around the Gulf of Mexico. The caterpillar is quite distinctive; it is covered with thick yellow to gray hairs.

A sting from the asp caterpillar often produces a grid-like pattern of hemorrhagic papulovesicles. Each red papule represents the site of direct cutaneous envenomation by the insect's poisonous hairs. Stings are intensely painful and can result in severe muscle cramps, intense headache, tachycardia, respiratory distress, convulsions, and shock.

This patient had no systemic symptoms other than paresthesias. The lesion healed completely within 10 days. Treatment of the stings is symptomatic and supportive.

Photo A depicts the larval, or caterpillar, stage of the corn emperor moth, Automeris io. This caterpillar's range extends from eastern Canada to the Atlantic coast, and along the shoreline bordering the Gulf of Mexico. Its sting results in hives localized around the contact site; the lesions typically resolve in 2 to 8 hours. Systemic symptoms are rare.

Photo B shows an imported fire ant. The 2 species found in the United States, Solenopsis richteri and Solenopsis invicta, are most common in the South. Fire ant venom initially induces a papular lesion that becomes a sterile pustule in about 24 hours. The pustules are associated with a painful burning or stinging sensation.