Abstract
Myiasis, an infestation of human tissue by fly larvae, can occur in travellers returning from endemic regions such as Africa and the Americas. In the head and neck, myiasis can result from infected periodontal disease, wounds or tumours, affecting both children and adults. Due to its rarity in the UK and slow progression, myiasis is often diagnosed late and can easily be misdiagnosed. We present a case of a 75-year-old woman who was stung by a venomous caterpillar, Lanomia Obliqua, whilst volunteering in Brazil. She developed non-healing wounds, initially thought to be a reaction to the caterpillar’s toxic spines, but was later diagnosed with myiasis. This case highlights the presentation, management, and potential diagnostic challenges associated with myiasis.
1
Introduction
Myiasis, an infestation of human tissue by fly larvae, is rare in the UK but is the fourth most common travel-related skin disease [ ]. The primary species responsible for human myiasis are Cordylobia Anthropophaga (Tumbu fly) from Africa and Dermatobia Hominis (human botfly) from the Americas [ ]. Risk factors include tropical travel and outdoor activity in humid environments [ ]. Maxillofacial cases can arise from infected periodontal disease, wounds or tumours [ , ]. Myiasis occurs when a fly lays eggs in open wounds, which hatch, grow and mature under the skin, resulting in a furuncular lesion. Symptoms include stinging sensations and movements within the wound. Diagnosis is typically made when there is no response to medical treatments, no systemic symptoms and swelling increases. In endemic areas, petroleum jelly is applied to suffocate the larvae [ , ].
2
Presentation
A healthy 75-year-old Caucasian woman presented to the Oral & Maxillofacial Surgery (OMFS) department after referral from her General Practitioner (GP). Seven weeks prior, whilst volunteering in Southern Brazil, she was stung on the lips by the venomous ‘Lanomia Obliqua’ caterpillar, which is known to cause fatalities [ ]. She sought medical attention in Brazil, and upon returning to the UK, visited her GP for increasing swellings on her lips (see Fig. 1 ). Following consultation with Liverpool School of Tropical Medicine, the GP prescribed a week of oral Flucloxacillin, but her condition did not improve, and she developed non-healing, weeping wounds with intermittent shock sensations. A referral to OMFS was made, with the likely diagnosis being a foreign body reaction to retained caterpillar spines.
Upon presentation to OMFS, the patient had a jar containing a living larva that had self-extricated from her upper lip. Clinical examination revealed no systemic involvement but noted three erythematous nodules (10–15mm in diameter) on her lips, with puncta that bled upon pressure.
3
Management
An urgent ultrasound showed two hypoechoic ovoid lesions extending from the mucosal to the submucosal layer: 13 × 5mm and 15 × 5mm, with mild oedema, increased echogenicity and no abscess formation. High-resolution colour Doppler sonography confirmed spontaneous movement of the larvae with a colourful mosaic pattern, and no surrounding blood flow disruption (see Fig. 2 ).
