Clinical History
A 53 year old man on holiday in Gambia after walking on the beach developed rapid onset of generalized swelling and pain, with five pustules on the dorsum of the foot and arch. He visited the accident and emergency department in the UK to exclude a thorn or some form of foreign body (FB) injury.
Imaging Findings
A plain radiograph performed did not show any radiopaque FB. Antibiotic cover with an US appointment to assess any underlying soft tissue FBs was scheduled.
The US performed on the next day demonstrated superficial widespread subcutaneous oedema and cellulitis extending through the dorsum and plantar aspects of the foot. Five pustular lesions on the dorsum of the foot appeared as rather ill defined hyperechoic ovoid structures with no localized hypoechoic inflammatory reaction. These were atypical of a classic FB (splinter or thorn). There was a little Doppler-signal artefact around the lesions but no definite movement. There was no obvious FB to retrieve. A follow-up appointment was arranged following a 5-day course of antibiotics.
His second US scan showed that the ill-defined hyperechoic area in the subcutaneous region under each pustular type lesion had increased in size with marked acoustic shadowing. There was suspicion of some movement in these areas but there was uncertainty as to whether this was due to local vascular pulsation or true movement. There was no improvement in the subcutaneous oedema and his symptoms persisted. One of these lesions was explored and de-roofed which revealed a live maggot approximately 4mm in length. All five lesions were then debrided and similar maggots were found in each lesion of different gestational evolution. These were sent to an entomoligist and were confirmed as maggots from the African Tumbu Fly.
The patient made a slow and uneventful recovery, the oedema settled and the lesions healed over the following weeks.
Discussion
More people travel for various purposes, bringing new presentations into Europe, previously limited to endemic areas. Little is known about the US atures of cutaneous parasitic diseases in humans. An extensive literature search found only a few cases. Parasitic infestation should be considered in the differential diagnosis of cutaneous and subcutaneous lesions and knowledge of their management is important to avoid unnecessary interventions and prevent possible complications.
Sonography enables differentiating these lesions from simple furuncles and in the assessment of viability of the larvae [1]. It enables differentiating these lesions from simple furuncle, assess viability of the larvae, and clarify the degree of cellulitis which is not seen with the typical foreign body and to recognise the larva itself. Frank movement on Colour Doppler may be seen [1-3]. US also can detect the number of larvae in each lesion, aiding in characterisation [3].
Cordylobia anthrophaga- is common in East and Central Africa [4]. It lays eggs in clothes hanging out to dry and upon contact with skin the eggs hatch. The larvae then burrow into the skin and develop into maggots. Adult flies are non-parasitic. Larvae are initially 0.5-1.5cm long and survive up to 15 days, remaining within a cavity in the dermis and hypodermis. This cavity communicates to the external environment by means of a central breathing pore, a single larva is found in each cavity. Larvae then emerge through the pore. Adult flies emerge 10-20 days later, and the cycle begins again.
Infestation presents as a small erythematous papule which enlarges until it becomes a nodule that resembles a furuncle, the centre of which has a pore oozing serous fluid.
Massive infestation may induce marked swelling and oedema. Larvae can penetrate deep into tissues and cause considerable damage and even death.
The presence of a dermal swelling with a central opening raises suspicion of myiasis in a patient with history of travel to endemic areas.
Ultrasonography clarifies the degree of cellulitis which is not seen with the typical FB and recognises the larva itself. This is more ill defined and rather ovoid compared to typical FB which tend to be more linear and hyperechoic. Frank movement on Colour Doppler may be seen [1,3]. US also detects the number of larvae per lesion, aiding in characterisation [3].
Treatment involves clogging the breathing pore with thick viscous compounds, such as liquid paraffin, causing larval hypoxia and so it leaves the cavity in search of oxygen.
Ultrasonographic follow up is then valuable in ensuring resolution with no remaining larvae within the tissues. Surgical excision is usually unwarranted while the larvae are alive but is used to remove dead or decaying larvae. Great care should be taken during the extraction, although anaphylaxis has not been reported.
This case highlights that parasitic infestations are brought to the UK from foreign travel and the unusual features with the extensive subcutaneous oedema should alert the sonographers to the possibility of a parasitic organism.
Differential Diagnosis List
African Tumbo Fly parasitic infestation to soft tissues.
Final Diagnosis
African Tumbo Fly parasitic infestation to soft tissues.
