LF MDA co-endemicity — DTM&H MCQ

Correct answer: E — DEC plus albendazole

The correct answer is E, DEC plus albendazole. In areas co-endemic for onchocerciasis and Loa loa, diethylcarbamazine (DEC) must be avoided in mass drug administration (MDA) for lymphatic filariasis because it rapidly kills microfilariae and can precipitate severe or fatal reactions. In onchocerciasis this causes intense Mazzotti-type reactions, and in individuals with high Loa loa microfilaraemia it can trigger fatal encephalopathy. WHO guidance therefore replaces the DEC-based regimen with ivermectin plus albendazole for MDA in these co-endemic settings, since ivermectin has a safer profile in this context despite requiring caution with heavy Loa loa loads. Why the other options are wrong: A. Ivermectin plus albendazole: this is the WHO-recommended alternative regimen precisely because it avoids DEC in onchocerciasis and Loa loa co-endemic areas, making it the safe standard of care, not the drug combination to avoid. B. Ivermectin alone: used in onchocerciasis MDA and tolerated in co-endemic settings; it is not the pairing implicated in the severe DEC-related reactions described in the stem. C. Albendazole alone: albendazole has minimal microfilaricidal activity and a favourable safety profile, so it is not associated with the severe adverse reactions seen with DEC. D. Doxycycline plus ivermectin: doxycycline targets Wolbachia and adult worms slowly without acute microfilarial killing, so this combination does not provoke the rapid microfilaricidal reactions that make DEC dangerous. Key point: DEC is contraindicated in areas co-endemic for onchocerciasis or Loa loa because rapid microfilarial killing risks Mazzotti reactions and fatal Loa encephalopathy, so ivermectin plus albendazole is used instead.

Reference: WHO. Guideline: Alternative Mass Drug Administration Regimens to Eliminate Lymphatic Filariasis. Geneva: World Health Organization; 2017. Available at: https://www.ncbi.nlm.nih.gov/books/NBK487826/