Onchocerca cervicalis in horses from southern Brazil.

The objective of this study was to determine the occurrence of Onchocerca cervicalis in 1200 adult horses from rural areas of Rio Grande do Sul, Brazil. Umbilical skin specimens measuring 2 x 2 cm were minced, suspended in 10 ml of distilled water and incubated at room temperature overnight. The liquid volume was centrifuged and the sediment was screened for microfilariae. The ligamentum nuchae were totally removed, preserved in ice and dissected for the detection of adult forms of Onchocerca cervicalis. Microfilariae of Onchocerca cervicalis were detected in midventral skin biopsy samples in 215 (17.9%) of 1200 horses examined and the adult worms were recovered from 200 (16.6%) ligamentum nuchae from the same animals. These findings provide a basis for further studies to determine infection rates in horses from other regions of the state and to identify the intermediate host that transmits the disease.