CUTANEOUS IN RETURNED TRAVELLERS

Sundac L1, Cherian S2, McDougall R2, Doggett SL3, Geary M3, Muller M4, Robson J2

1Advanced Trainee, Infectious Diseases & Microbiology, Princess Alexandra Hospital, 2Microbiologist, Sullivan Nicolaides Pathology, Queensland, 3Senior Hospital Scientist, Department of Medical Entomology, Pathology West, Westmead Hospital, New South Wales 4Senior Medical Entomologist, and Pest Management, Brisbane Infrastructure, Brisbane City Council

Figure 1: Life cycle of . Figure 2: 1st, 2nd, early and late 3rd instar larvae INTRODUCTION http://www.cdc.gov/dpdx/ of Dermatobia hominis illustrative of larvae found in Cutaneous myiasis is generally caused by obligatory parasitic species that can penetrate cases 1-3. Photograph by Marty FM et al Brigham and unbroken skin or enter through small perforations in the skin or hair follicles. This gives rise to Women’s Hospital, Boston, MA. an enlarging lesion resembling a furuncle, which opens externally allowing the to breathe. The most common agents of cutaneous myiasis are Dermatobia hominis and anthropophaga. With more frequent international travel there is an increasing risk of these being imported into Australia. We summarise four cases that have been diagnosed in travellers over the past 10 years in Brisbane.

Table 1: Clinical and Laboratory data at presentation

Case 1 Case 2 Case 3 Case 4 Figure 3: Case 2. Furuncular myiasis Figure 4: Case 2. Lesion with central opening, secondary to Dermatobia hominis. typical of cutaneous myiasis. Demographics 61M 26F 59F 61M

Travel Holiday to: Holiday to Peruvian Ica, Southern Peru Goma, Democratic Republic Peruvian Amazon Amazon, 3 week trip of the Congo Visit to horse fair La Paz, Bolivia Volunteer health care Brazil, Argentina worker, 2 week trip

Risk factors Endemic area Endemic area Endemic area Endemic area; contact (dog with Animal contact Used local laundry; confirmed myiasis) (horses) Clothes not always ironed

Clinical features Furuncle on 3 lesions noted during 2 bites on left ear 2 days after return home, Figure 6: The distribution of C.anthropophaga is between shoulder after trip. Enlarged over three and scalp. noted 2 furuncles on his the dotted lines. The shaded areas show the distribution returning home weeks into boils with Enlarged to boils back. Enlarged over 1 week, of C. rodhani, another species in the same . Photo external opening with central opening; developed central opening Credit: Geary M et al “Exotic myiasis with Lund’s fly.” Purulent exudate purulent exudate with purulent exudate Medical Journal of Australia 171 (1999): 654-655. Lancinating pain Crawling sensation Management Removal of Removal of larvae aided Lesions excised; Fly larvae expelled with larva aided by by occlusion of external each contained a gentle pressure application of opening with single larva Bacterial super infection, drawing ointment petroleum jelly resolved with antibiotics Figure 5: Dermatobia Histology N/A Burrow in dermis N/A N/A hominis is indigenous Surrounding inflammatory from Mexico in the north infiltrate comprising to Paraguay and northeast neutrophils, Argentina in the south. Drawing by eosinophils and Connelly CR, University of Florida. lymphohistiocytes Speciation Dermatobia Dermatobia Dermatobia Cordylobia hominis hominis hominis anthropophaga DISCUSSION Dermatobia hominis (New World bot fly) is neotropical in distribution (Figure 5) and, despite its name, can infest many species. The most common hosts for the bot fly are cattle and dogs. However, they are found in many warm-blooded including buffalo, cattle, cats, dogs, , monkeys, pigs, rabbits, and sheep. It is transmitted by mosquitoes and other blood-feeding and is unique in being an -borne arthropod (Figure 1)! Figure 7: Moulting early 3rd instar larva of Figure 8: 3rd and early Adults lay their eggs on the body of a mosquito or another blood sucking arthropod. The larvae Cordylobia anthropophaga obtained from 2nd stage larvae (Photo S.Doggett). hatch while the vector takes a blood meal and enter the skin at the bite site. Larvae develop Case 4. cutaneously and subcutaneously but do not migrate from their initial site of inoculation. The third instar larvae, which can grow to be relatively large, crawl out of the host to pupate in the CONCLUSION Cutaneous myiasis is an ectoparasitic of tissues by fly larvae. Exotic soil. In general, the life of the larvae inside the host is 5 to 12 weeks. The larvae feed on tissue furuncular myiasis in travellers is most commonly caused by the New World exudates. Dermatobia in the tropical and subtropical areas of the and the Cordylobia anthropophaga (the African tumbu fly and Greek for “eater of men”) is distributed Tumbu fly Cordylobia in Africa as these 4 cases illustrate. Removal of the intact larva in tropical Africa (Figure 6) and is an obligatory parasite in humans. Cordylobia females do not is curative. Various measures have been described to asphyxiate the larvae resulting lay their eggs directly on the human host but rather on dry sand or other fomites (including in their rapid removal without the need for extensive excision and extraction. clothing or bedding that is hung out to dry after laundering). Many animals are hosts of As well as infesting humans, these exotic fly larvae commonly attack domestic C.anthropophaga. The dog is the most common domestic host and several species of wild rats livestock inflicting severe trauma and economic losses. With increased global travel are the preferred field hosts. and the popularity of many new tourist destinations, vigilance is required to avoid the risk of these and other exotic parasitic (especially New World and Old World screw worms) becoming introduced into Australia.