A Rare Case of Loa loa Filariasis

Prompt

Based on the following abstract please make an academic poster. Leave space for authors, 2 images, a QR code showing a video of the worm ABSTRACT Loa loa filariasis, or loiasis, is a parasitic disease caused by the nematode Loa loa, also known as the African Eye Worm. The disease is endemic to regions of West and Central Africa and is transmitted through bites from the Chrysops fly. Strikingly, the 2-7cm long adult Loa loa worm can migrate through subcutaneous tissues and is known to be visualised in and around the ocular tissues. The clinical spectrum also includes asymptomatic eosinophilia and episodic localised subcutaneous angioedema, known as ‘Calabar swelling’. There are diagnostic challenges associated with loiasis. Cases outside endemic areas are rare therefore recognition by a clinician familiar with the condition is paramount. In addition, the ocular migration of the worm is transient, and the patient may be asymptomatic. However, left untreated, the parasite can live in the host for up to 17 years and complications such as blindness or encephalitis can occur. Here we describe the diagnosis and treatment of a case of Loa loa that initially presented to an eye casualty in the United Kingdom. We also present photographs and video footage of the live worm, as it was visualised in the subconjunctival space, which is known to be a rare observation. CASE PRESENTATION A 48-year-old male presented to eye casualty at a tertiary care hospital with a one-day history of left eye discomfort and foreign body sensation. A patient’s relative reported observing a live worm moving on the surface of the eye and provided video footage of this. He was originally from Nigeria and moved to the UK two years prior to his presentation. On examination, the patient had mild left eye conjunctival injection, with otherwise normal anterior and posterior ocular segments. Despite a thorough search, there was no worm visualised clinically. He was reviewed by the local infectious disease team, where he was investigated further and subsequently referred to the Hospital for Tropical Diseases in London. A history of transient hand swellings, resembling ‘Calabar swellings’, along with eosinophilia were noted. Filarial antigen was positive on serological testing, and the daytime blood film was negative for microfilaria. Clinically this was consistent with Loa loa. Concurrent infection with onchocerciasis was excluded with skin snips. The patient was treated successfully with diethylcarbamazine. He remains closely monitored, with no reported side effects or signs of recurrence. DISCUSSION This case highlights the diagnostic challenge of loiasis presenting to a UK-based eye casualty. The final diagnosis relied on input from a multidisciplinary team across multiple hospital sites, utilising information from the patient’s clinical history, biochemical, serological and microbiological tests. There are only occasional reports of loiasis in Europe since the early 2000s, and yet it is possible this disease is under-diagnosed due to lack of knowledge from healthcare professionals in non-endemic areas. Importantly, one must exclude concurrent infection with onchocerciasis (river blindness) prior to initiating treatment, as a fatal encephalitic reaction can occur with treatment in patients co-infected with both parasites. This patient’s successful diagnosis and treatment may be useful learning for ophthalmology, infectious disease, emergency department and global health colleagues to aid prompt recognition, work up and referral of this condition. CONCLUSION Loa loa should be considered in patients from endemic regions presenting with ocular symptoms in non-endemic areas. Ophthalmologists should be aware they may see the patient at first presentation, and referral on to infectious diseases/tropical medicine services is paramount to ensure appropriate investigations are performed to aid appropriate management.

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