Electron microscopical studies on onchocerciasis. II. Skin and microfilariae after treatment with metrifonate.

Skin snips of six patients with manifest onchocerciasis treated with a single dose of metrifonate (10 mg/kg) were examined by electron microscopy one, three, five and ten days after application of the drug. Compared to untreated cases 24 hours after treatment there is a marked increase in the extend of perivascular infiltrates which are composed not only of macrophages, lymphocytes and plasma cells, but also of eosinophils. Infiltrates directly around dead microfilariae are seen infrequently. This pattern of cellular reaction remains constant for the first ten days after treatment. Metrifonate obviously kills the microfilariae rapidly, already 24 hours after its application totally disintegrated parasites are to be found. On the other hand always a few intact microfilariae are seen, possibly they just hatched after treatment.