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Loa loa Microfilarial Count Safety — SCE Infectious Diseases MCQ

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HardParasitologyLoa loa Microfilarial Count SafetySCE Infectious Diseases

A 30-year-old woman from West Africa presents with a 2-year history of intermittent subcutaneous swellings on her arms that migrate (Calabar swellings) and episodes of subconjunctival worm passage. Blood film (midday sample) shows sheathed microfilariae. Eosinophil count is 5.5 × 10⁹/L. Microfilarial count is 12,000/mL. Why must the microfilarial count be assessed before treatment?

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Correct answer: B — High microfilarial loads (>8,000/mL) of Loa loa risk fatal encephalopathy with DEC or Ivermectin — Albendazole should be used first to reduce the count before definitive treatment

Loa loa with high microfilaraemia (>8,000/mL for DEC; >30,000/mL for Ivermectin according to some guidelines, but >8,000 is the widely used threshold) carries a serious risk of fatal post-treatment encephalopathy. Rapid microfilarial killing releases antigens causing massive cerebral inflammation. Albendazole 200 mg BD for 21 days gradually reduces microfilarial counts without the encephalopathy risk, bringing levels below the safety threshold before definitive treatment with DEC. This step is critical and potentially lifesaving.

Reference: WHO 2022 – Loa loa; UKHSA 2023 – Filariasis