microfilaricidal

Microfilaricidal refers to a drug or agent that kills microfilariae, the first larval stage of certain filarial nematodes that circulate in the human bloodstream or reside in tissues. Microfilaricides target the microfilariae rather than the adult worms (macrofilariae), and their primary public health role is to reduce transmission by preventing vectors from picking up viable microfilariae.

These agents are used in the treatment and control of diseases such as lymphatic filariasis, onchocerciasis, and loiasis. Ivermectin is a widely used microfilaricide, particularly effective against the microfilariae of Onchocerca volvulus and Wuchereria bancrofti, and is a cornerstone of mass drug administration programs in endemic regions. Diethylcarbamazine is another influential microfilaricide with activity against multiple species but can provoke strong inflammatory reactions as dying microfilariae release antigens. Some regimens combine microfilaricidal drugs with agents that affect adult worms or fertility to enhance long-term control.

Mechanistically, ivermectin binds parasite glutamate-gated chloride channels, causing paralysis and death of microfilariae. Diethylcarbamazine’s action is partly immunomodulatory, increasing host clearance of microfilariae. The exact mechanisms vary by drug and parasite species, and not all microfilaricides have substantial macrofilaricidal effects; some regimens rely on sterilizing or slowing the reproduction of adult worms.

Adverse reactions can occur when large numbers of microfilariae die, including the Mazzotti reaction or ocular inflammation. Caution is advised in infections such as loiasis, where rapid microfilarial death can lead to severe complications.