Sunday, January 20, 2019

Answer to Case 528

Answer to Case 528: Botfly larva; clinical presentation is consistent with furucular myiasis. As Blaine and others have mentioned, "the epidemiology supports this being the 'Tumbu fly', Cordylobia anthropophaga. Cordylobia rodhani is also in Tanzania but less-commonly documented as a source of human myiasis." From a clinical standpoint, the presence of multiple furuncular lesions is also consistent with C. anthropophaga; this fly lays eggs its eggs on soil or damp clothing (e.g. those hanging on a line to dry).  The eggs hatch when they come into contact with the skin of the host, and the larvae burrow into the skin to cause furuncles. This is why clothing should be ironed in endemic areas after being taken off the clothes line; ironing destroys the eggs and prevents infection.

Blaine further mentions that the "morphologic features shown in the cuts include the gut, tracheae, and striated musculature. Unlike with tungiasis, eggs are not present as this is a sexually-immature larva. The yellow spines are indeed the cuticular spices; sclerotized chitin (a carbohydrate in the arthropod exoskeleton) usually stains yellow in H&E)."

Unfortunately we don't have the intact larva to identify. Idzi mentioned that "for differentiation of C. anthropophaga from C. rodhani, I’d like to see the spiracular slits as the ones for rodhaini are sinusoidal. Strong pigmentation of the spines suggests anthropophaga though. Rodhaini also is very exceptional..."

Finally, Bernardino, Nema and others mentioned that excision is not necessary for treatment. Instead, the easiest way to remove the larva is to first occlude the opening of the furuncle (through which the larva breathes) with an occlusive substance like petroleum jelly or soap paste (see Case of the Week 408 for a great example of Dermatobia hominis larva removal). After a short period of time, the larva can be removed by simply squeezing the lesion.

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