Fly Caught in Foreskin: An Usual Case of Preputial Myiasis

Abstract

Cutaneous bot fly infestation is common in travellers to Mexico and Central America. Myiasis affecting the genitalia is rare, however, with few previous reports. We document an unusual case in Nottingham, UK

A 29-year-old male presented with a 6-week history of localised preputial swelling, having sustained numerous insect bites in Belize, including one bite on the affected area. Although painless, the swelling caused some discomfort and exuded a yellowish fluid from a small hole in the side. No improvement had been observed with flucloxacillin treatment.

On examination, a discrete 2-cm swelling was observed affecting the prepuce, without erythema orfluctuation (Fig. 1). Suspecting something out of the ordinary for a Nottingham urology on-call, the advice of the infectious diseases registrar was sought, and a provisional diagnosis of myiasis (an invading fly larva) was made.

Figure 1.

A bot fly ’warble‘ affecting the foreskin, with breathing hole (arrow).

The skin over the lump was subsequently incised under local anaesthetic, and a bot fly larva was retrieved (Figs 2 and 3).

Figure 2.

Incision of the warble reveals the bot fly larva within.

Figure 3.

Bot fly larva following removal.

Discussion

Bot flies (Dermatobia hominis) are large, hairy flies resembling bumblebees. The bot fly egg is deposited on a mosquito (or, in this case, more likely a sandfly), which inadvertently deposits the eggs when it bites. The larvae grow in the subdermis forming a lump called a ‘warble’. The hole allows the larva to breathe, and the larva can be suffocated by occluding the hole with Vaseline. This manoeuvre was attempted by our patient prior to excision, inducing considerable wriggling of the larva, which subsequently peeped out through the hole to investigate.

Cutaneous bot fly infestation is common in travellers to Mexico and Central America. Myiasis affecting the genitalia is rare, however, with few previous reports.^1,2

For prospective travellers, advice from a local medic, Mr Peter Singfield of Xaibe Village, Belize, is available:³

Just take a little tobacco – or even heavily camphorated oil soaked in a small cotton packing – tape over vent hole – the worm comes out – 8 hours later pull off the tape – voila – one grub – no infection – everything OK.

You know – here – in every village – they have one or two people that are very good at squeezing them out. They have to feel first – to line up the grub properly – then they squeeze in a special way – a real ‘art’ – and the worm just pops out – shooting ten feet or more – like from a gun.

Surgical excision is perhaps preferable for the less experienced practitioner.