Tungiasis — DTM&H MCQ

Correct answer: C — Tunga penetrans flea

The correct answer is C, Tunga penetrans flea. This sand flea (jigger flea), endemic across sub-Saharan Africa, has a gravid female that burrows into the epidermis, typically of the feet or lower legs, and becomes progressively distended with eggs over days to weeks, producing a firm, painless to mildly tender nodule with a central punctum. The slow growth over months, the shin location, and the finding of a gravid arthropod with a distended white abdomen on extraction are classic for tungiasis rather than any other ectoparasitosis. Females lack specialised burrowing organs; they claw into the skin and remain fixed there while feeding and laying eggs, explaining the deeply embedded, sessile lesion. Management is sterile extraction of the intact flea plus tetanus prophylaxis, given the risk of secondary bacterial infection and tetanus. Why the other options are wrong: B. Cordylobia anthropophaga larva: causes a tumbu fly myiasis boil with a central breathing pore discharging fluid and a mobile larva, evolving over days, not a static gravid arthropod over three months. D. Sarcoptes scabiei mite: produces widespread pruritic burrows in web spaces and flexures, not a single firm nodule, and is microscopic, not a visible gravid arthropod. A. Ixodes tick: attaches externally to feed for days then detaches; it does not embed within the epidermis or form a slowly enlarging nodule. E. Dermatobia hominis larva: the New World botfly causing myiasis in Central and South America, not Cameroon, presenting as a painful furuncular lesion with a discharging larva, not a static gravid flea. Key point: A slowly enlarging, deeply embedded, painless nodule yielding a gravid arthropod with a distended white abdomen is pathognomonic for tungiasis (Tunga penetrans).

Reference: UCLH NHS Foundation Trust, Removal of bot/tumbu flies and jigger fleas, patient information (tungiasis extraction guidance). https://www.uclh.nhs.uk/patients-and-visitors/patient-information-pages/removal-bottumbu-flies-and-jigger-fleas