Onchocerca cervicalis infection in horses from the western United States.

In a study of Onchocerca cervicalis infection in a sample of 100 horses from the western United States, 48 were infected. Infection was more common in older horses and occurred in both sexes equally. Data about the distribution and the concentration of microfilariae within the skin are presented. The only cutaneous pathologic change that could be attributed to microfilariae was minimal perivascular inflammatory cell infiltrate. Invasion of the eye with microfilariae occurred in 60 percent of the infected horses. An attempt was not made to relate microfilarial invasion of the eye with ocular pathologic changes.