Mazzotti Reaction

The Mazzotti reaction is a set of severe symptoms that can occur in people with onchocerciasis, also called river blindness, shortly after they are treated with the antiparasitic drug diethylcarbamazine. The reaction happens because the drug rapidly kills large numbers of the microfilariae, the immature larval form of the parasitic worm Onchocerca volvulus, circulating in the skin, and the sudden immune response to the dying larvae produces fever, intense itching, swollen lymph nodes, skin rash and, in severe cases, swelling around the eyes that can threaten vision. It is named for the Italian physician Luigi Mazzotti, who first documented the reaction in the 1940s. Because of this risk, diethylcarbamazine is no longer used to treat onchocerciasis in most of the world, and it has largely been replaced by ivermectin, which kills the microfilariae more gradually and produces a milder reaction.