The Sting of a White Flannel Moth Caterpillar (Norape ovina)

Abstract

The purpose of this report is to describe a case of urticarial dermatitis, or erucism, caused by the white flannel moth caterpillar (Norape ovina) in central Virginia. Many caterpillars are known to cause erucism, with the puss caterpillar (Megalopyge opercularis) being the most reported culprit in the United States. White flannel moth caterpillars are expected to cause erucism as they belong to the same family as the puss caterpillar (Megalopygidae) and have similar venom-containing hairs, but no reports of the reaction or clinical course have been documented in the medical literature. A subject was stung by a white flannel moth caterpillar after it fell on his neck while clearing brush with a machete. The subject experienced immediate pain and developed a raised, erythematous rash where the caterpillar had fallen. The rash, referred to as erucism, was painful for 1 d and improved slowly over the course of 2 wk, but a small area of discoloration remained 2.5 mo after contact. Symptoms were managed by the subject at home and no medications were administered. The white flannel moth caterpillar inflicts erucism similar to that caused by the more commonly mentioned puss caterpillar. If only local symptoms are sustained from contact with a white flannel moth caterpillar, it can be safely and effectively managed with over-the-counter medications similar to the management for erucism induced by other caterpillar species. Irrigation and removal of urticating hairs with adhesive tape may help reduce the pain and is recommended, though not performed in this case.

Keywords: Lepidopterism; erucism; stinging caterpillar; urticarial dermatitis; urticating hairs.