Onchocerciasis: experimental models of ocular disease

Onchocerciasis is a leading cause of blindness in equatorial Africa and in endemic regions in Central America. Understanding of the pathologic processes involved in onchocercal eye disease and of the role of immunopathologic mechanisms in its development has been substantially limited by the shortage of eyes for histologic study and by the lack of a naturally occurring animal model. The inoculation of microfilariae of Onchocerca species into the eyes of laboratory animals may reproduce selected aspects of onchocercal eye disease, such as punctate keratitis. Studies in these models support the hypothesis that immunopathologic mechanisms mediated by IgE antibody are involved in the development of ocular lesions. In some laboratory animal models, diethylcarbamazine citrate, a microfilaricidal drug that causes severe inflammatory reactions to microfilariae in humans, increases the severity of ocular lesions, and stimulates IgE antibody responses. Laboratory animal studies are potentially highly useful for understanding the immunopathogenesis of ocular onchocerciasis.