Furuncular Myiasis in 2 American Travelers Returning From Senegal

Case Reports

Patient 1

A 16-year-old adolescent boy presented to the emergency department with painful, pruritic, erythematous nodules on the bilateral legs of 1 week’s duration. The lesions had developed 1 week after returning from a monthlong trip to Senegal with a volunteer youth group. He did not recall sustaining any painful insect bites or illnesses while traveling in Africa and only noticed the erythematous papules on the legs when he returned home to the United States. After consulting with his primary care physician and a local dermatologist, the patient began taking oral cephalexin for suspected bacterial furunculosis with no considerable improvement. Over the course of 1 week, the lesions became increasingly painful and pruritic, prompting a visit to the emergency department. Prior to his arrival, the patient reported squeezing a live worm from one of the lesions on the right ankle.

On presentation, the patient was afebrile (temperature, 36.7°C) and his vital signs revealed no abnormalities. Physical examination revealed tender erythematous nodules on the bilateral heels, ankles, and shins with pinpoint puncta noted at the center of many of the lesions (Figure 1). The nodules were warm and indurated and no pulsatile movement was appreciated. The legs appeared to be well perfused with intact sensation and motor function. The patient brought in the live mobile larva that he extruded from the lesion on the right ankle. Both the departments of infectious diseases and dermatology were consulted and a preliminary diagnosis of furuncular myiasis was made.

^{Figure 1. Tender erythematous nodules on the bilateral heels, ankles, and shins.}

The lesions were occluded with petroleum jelly and the patient was instructed to follow-up with the dermatology department later that same day. On follow-up in the dermatology clinic, the tips of intact larvae were appreciated at the central puncta of some of the lesions (Figure 2). Lidocaine adrenaline tetracaine gel was applied to lesions on the legs for 40 minutes, then lidocaine gel 1% was injected into each lesion. On injection, immobile larvae were ejected from the central puncta of most of the lesions; the remaining lesions were treated via 3-mm punch biopsy as a means of extraction. Each nodule contained only a single larva, all of which were dead at the time of removal (Figure 3). The wounds were left open and the patient was instructed to continue treatment with cephalexin with leg elevation and rest. Pathologic examination of deep dermal skin sections revealed larval fragments encased by a thick chitinous cuticle with spines that were consistent with furuncular myiasis (Figures 4 and 5). Given the patient’s recent history of travel to Africa along with the morphology of the extracted specimens, the larvae were identified as Cordylobia anthropophaga, a common cause of furuncular myiasis in that region.

Patient 2

The next week, a 17-year-old adolescent girl who had been on the same trip to Senegal as patient 1 presented with 2 similar erythematous nodules with central crusts on the left inner thigh and buttock. On noticing the lesions approximately 3 days prior to presentation, the patient applied topical antibiotic ointment to each nodule, which incited the evacuation of white tube-shaped structures that were presented for examination. On presentation, the nodules were healing well. Given the patient’s travel history and physical examination, a presumptive diagnosis of furuncular myiasis from C anthropophaga also was made.

Figure 2. The tips of intact larvae were appreciated at the central puncta of some of the lesions following occlusion with petroleum jelly. Figure 3. Dead larva extracted by lidocaine injection and punch biopsy.

Comment

The term myiasis stems from the Greek term for fly and is used to describe the infestation of fly larvae in living vertebrates.¹ Myiasis has many classifications, the 3 most common being furuncular, migratory, and wound myiasis, which are differentiated by the different fly species found in distinct regions of the world. Furuncular myiasis is the most benign form, usually affecting only a localized region of the skin; migratory myiasis is characterized by larvae traveling substantial distances from one anatomic site to another within the lower layers of the epidermis; and wound myiasis involves rapid reproduction of larvae in necrotic tissue with subsequent tissue destruction.²

The clinical presentation of the lesions noted in our patients suggested a diagnosis of furuncular myiasis, which commonly is caused by Dermatobia hominis, C anthropophaga, Cuterebra species, Wohlfahrtia vigil, and Wohlfahrtia opaca larvae.³Dermatobia hominis is the most common cause of furuncular myiasis and usually is found in Central and South America. Our patients likely developed an infestation of C anthropophaga (also known as the tumbu fly), a yellow-brown, 7- to 12-mm blowfly commonly found throughout tropical Africa.³ Although C anthropophaga is historically limited to sub-Saharan Africa, there has been a report of a case acquired in Portugal.⁴