Case In Point: Man With Tender Furunculoid Lesions

A 37-year-old man presents for evaluationof 3 reddish, tender, 2-cm, elevatedlesions on his right ankle that havefailed to respond to oral amoxicillin/clavulanate prescribed by anotherphysician. The lesions have beenpresent for 8 weeks. Each lesion has acentral opening and watery yellow drainage (Figure 1). The patient recentlyreturned from a trip to CentralAmerica, where he had sustained multiplemosquito bites.

He reports that a nurse advisedhim to cover the openings of the lesionswith petroleum jelly. A botfly larva latercrawled out of his skin, but the otherlarvae remained in the lesions.

After a local anesthetic is injected,the 2 remaining larvae are extractedwith forceps (Figure 2). The patientrecovers quickly after the larvaeare removed.

MYIASIS: AN OVERVIEW

The human botfly (Dermatobiahominis) causes myiasis, or infestationof the skin with fly larvae. In rarecases, humans may become infestedby other botfly species. Transmissionrequires a human or other vertebrate host. The gravid female fly attacheseggs onto the abdomen of a mosquitoor bloodsucking fly. When the carrierinsect (or vector) bites a human orother host, the eggs are transferredto the skin. Larvae hatch and burrowthrough the skin, forming an inflamednodule called a warble. The larvaefeed on the host but must maintain an air hole to breathe. Once mature, thelarvae exit the warble through the airhole, fall off the host, and developinto pupae and eventually adult flies.

Development of the human botflyfrom egg to mature maggot usuallytakes about 6 to 8 weeks. The infestationis benign, although a local bacterialinfection may develop.

MANAGEMENT

Occlusion of the punctum withpetrolatum or raw meat may inducethe larvae to exit the skin to avoid asphyxiation.Manual extraction may berequired.