Furuncular Myiasis in 2 American Travelers Returning From Senegal

In a review of the literature, C anthropophaga myiasis was documented in Italian travelers returning from Senegal^5-7; our cases are unique because they represent North American travelers returning from Senegal with furuncular myiasis. Furuncular myiasis from C anthropophaga has been reported in travelers returning to North America from other African countries, including Angola,⁸ Tanzania,^9-11 Kenya,⁹ Sierra Leone,¹² and Ivory Coast.¹³ Several cases of ocular myiasis from D hominis and Oestrus ovis have been reported in European travelers returning from Tunisia.^14,15

Tumbu fly infestations typically affect dogs and rodents but can arise in human hosts.³ Children may be affected by C anthropophaga furuncular myiasis more often than adults because they have thinner skin and less immunity to the larvae.²

Figure 4. Deep dermal cavity containing larval fragments encased by a thick chitinous cuticle with spines surrounded by mixed dermal inflammation (H&E, original magnification ×40). Figure 5. Larval intestinal components were visualized as well as striated muscle (H&E, original magnification ×200).

There are 2 mechanisms by which infestation of human hosts by C anthropophaga can occur. Most commonly, female flies lay eggs in shady areas in soil that is contaminated by feces or urine. The hatched larvae can survive in the ground for up to 2 weeks and later attach to a host when prompted by heat or movement.³ Therefore, clothing set out to dry may be contaminated by this soil. Alternatively, female flies can lay eggs directly onto clothing that is contaminated by feces or urine and the larvae subsequently hatch outside the soil with easy access to human skin once the clothing is worn.²

Common penetration sites are the head, neck, and back, as well as areas covered by contaminated or infested clothing.^2,3 Penetration of the human skin occurs instantly and is a painless process that is rarely noticed by the human host.³ The larvae burrow into the skin for 8 to 12 days, resulting in a furuncle that occasionally secretes a serous fluid.² Within the first 2 days of infestation, the host may experience symptoms ranging from local pruritus to severe pain. Six days following initial onset, an intense inflammatory response may result in local lymphadenopathy along with fever and fatigue.² The larvae use their posterior spiracles to create openings in the skin to create air holes that allow them to breathe.³ On physical examination, the spiracles generally appear as 1- to 3-mm dark linear streaks within furuncles, which is important in the diagnosis of C anthropophaga furuncular myiasis.^1,3 If spiracles are not appreciated on initial examination, diagnosis can be made by submerging the affected areas in water or saliva to look for air bubbles arising from the central puncta of the lesions.¹

All causes of furuncular myiasis are characterized by a ratio of 1 larva to 1 furuncle.¹⁶ Although most of these types of larvae that can cause furuncular myiasis result in single lesions, C anthropophaga infestation often produces several furuncles that may coalesce into plaques.^1,2 The differential diagnosis for C anthropophaga furuncular myiasis includes pyoderma, impetigo, staphylococcal furunculosis, cutaneous leishmaniasis, infected cyst, retained foreign body, and facticial disease.^2,3 Dracunculiasis also may be considered, which occurs after ingestion of contaminated water.² Ultrasonography may be helpful for the diagnosis of furuncular myiasis, as it can facilitate identification of foreign bodies, abscesses, and even larvae in some cases.¹⁷ Definitive diagnosis of any type of myiasis involves extraction of the larva and identification of the family, genus, and species by a parasitologist.¹ Some experts suggest rearing preserved live larvae with raw meat after extraction because adult specimens are more reliable than larvae for species diagnosis.¹

Treatment of furuncular myiasis involves occlusion and extraction of the larvae from the skin. Suffocation of the larvae by occlusion of air holes with petroleum jelly, paraffin oil, bacon fat, glue, and other obstructing substances forces the larvae to emerge in search of oxygen, though immature larvae may be more reluctant than mature ones.^2,3 Definitive treatment involves the direct removal of the larvae by surgery or expulsion by pressure, though it is recommended that lesions are pretreated with occlusive techniques.^1,3 Other reported methods of extraction include injection of lidocaine and the use of a commercial venom extractor.¹ It should be noted that rupture and incomplete extraction of larvae can lead to secondary infections and allergic reactions. Lesions can be pretreated with lidocaine gel prior to extraction, and antibiotics should be used in cases of secondary bacterial infection. Ivermectin also has been reported as a treatment of furuncular myiasis and other types of myiasis.¹ Prevention of infestation by C anthropophaga includes avoidance of endemic areas, maintaining good hygiene, and ironing clothing or drying it in sunny locations.^1,2 Overall, furuncular myiasis has a good prognosis with rapid recovery and a low incidence of complications.¹