A retrospective analysis of 96 "asp" (Megalopyge opercularis) envenomations in Central Texas during 1996

The most frequently reported caterpillar envenomation in Central Texas is by the puss caterpillar or "asp," Megalopyge opercularis. This caterpillar is described by patients and physicians as inflicting intense radiating pain. The intensity of symptoms may be underestimated leading to undertreatment. Adequate treatment protocols have been lacking and those in use are not very successful. We present a retrospective study of patients who were stung and contacted the Central Texas Poison Center.

All human exposures to asp stings reported to the Central Texas Poison Center during 1996 were included. Inclusion criteria consisted of all cases documented as an asp envenomation by the specialists in poison information. Characterization of symptoms and treatment used were evaluated.

There were 96 exposures to asps reported. Ninety-five of the patients experienced local pain with 26 of these reporting intense radiating pain. Forty developed erythema, 27 described edema, and 9 complained of welts/hives. Other symptoms reported included white spots (4), pruritus (3), red streak (2), numbness (2), and individual accounts of chest pain, rash, ecchymosis, tingling, blister, and muscle spasm. There was no treatment modality that promptly relieved pain.

Although asp envenomations appear to be very common, clinical cases have rarely been documented. This may be due to physicians not recognizing the etiological agent. Pain may be very intense and standard pain management appears to be unsuccessful.

This study suggests that further examination of treatment modalities may be beneficial in addressing the morbidity of Megalopyge opercularis envenomations.