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Anti-Wolbachia Onchocerciasis — SCE Infectious Diseases MCQ

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HardTropical & Imported InfectionsAnti-Wolbachia OnchocerciasisSCE Infectious Diseases

A 30-year-old man from Cameroon presents with subcutaneous nodules on his lower limbs and chronic pruritic papular rash. Skin snip from the iliac crest shows microfilariae. He has early corneal changes on slit-lamp examination (punctate keratitis). What anti-filarial strategy targets the adult worms rather than just microfilariae?

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Correct answer: A — Doxycycline 100 mg BD for 4–6 weeks (anti-Wolbachia endosymbiont therapy) — this has macrofilaricidal activity, killing adult worms

Standard Ivermectin treatment for Onchocerciasis is microfilaricidal only — it kills microfilariae but does not kill adult worms, necessitating repeated dosing every 6–12 months. Doxycycline 100 mg BD for 4–6 weeks targets the Wolbachia endosymbiont bacteria within the adult worm. Wolbachia are essential for O. volvulus fertility and survival — their elimination leads to adult worm sterilisation and eventual death (macrofilaricidal effect). This strategy reduces the need for lifelong repeated Ivermectin. DEC is contraindicated in Onchocerciasis as it causes severe Mazzotti reaction.

Reference: WHO 2022 – Onchocerciasis; Lancet ID 2019 – Anti-Wolbachia strategy