Gnathostomiasis — DTM&H MCQ

Correct answer: B — Albendazole or ivermectin

The correct answer is B, albendazole or ivermectin. The vignette describes cutaneous gnathostomiasis, acquired from eating raw or undercooked freshwater fish (a classic feature of Thai dishes such as koi pla), presenting with intermittent migratory subcutaneous swellings and marked eosinophilia due to Gnathostoma spinigerum larvae migrating through subcutaneous tissue. This clinical picture, well documented in UK returning travellers seen at the Hospital for Tropical Diseases, London, is treated medically with albendazole 400 mg twice daily for two to three weeks or ivermectin, both of which are effective larvicidal agents, with surgical extraction reserved for accessible palpable lesions. There is no first-line role for antifungals, antimalarials or antiprotozoal fluke drugs in this nematode infection, so recognising the exposure history and eosinophilic migratory swelling pattern is what should drive selection of D. Why the other options are wrong: C. Fluconazole: This is an antifungal with no activity against helminths; it has no role in gnathostomiasis, which is a larval nematode infection, not a fungal disease. A. Oral rehydration: This is supportive management for dehydrating gastrointestinal illness such as cholera or acute diarrhoea, not a specific antiparasitic treatment, and does not address tissue-invasive larvae. E. Chloroquine: This is an antimalarial acting on Plasmodium species within red blood cells; it has no larvicidal or antihelminthic action against Gnathostoma. D. Praziquantel: This is effective against trematodes and cestodes (flukes and tapeworms) by disrupting calcium homeostasis in their tegument, but Gnathostoma is a nematode against which praziquantel has no reliable activity. Key point: Migratory subcutaneous swellings with eosinophilia after raw freshwater fish ingestion in a returning Southeast Asian traveller signals gnathostomiasis, treated with albendazole or ivermectin, not praziquantel.

Reference: Hospital for Tropical Diseases, London (PMC8991338): Case Report: Gnathostomiasis Acquired in a Returning Traveler, describing albendazole and ivermectin as the well-recognised effective therapies for cutaneous gnathostomiasis. https://pmc.ncbi.nlm.nih.gov/articles/PMC8991338/