Development of microfilariae of two bovine Onchocerca species in blackflies in Japan.

Abstract

Injections of blackflies with two types of bovine Onchocerca microfilariae (so far regarded as different stages of O. gutturosa) obtained from engorged Simulium spp. and umbilical skins of a slaughtered cattle in Oita, Japan, were carried out to determine whether they can develop in blackflies to the third-stage larvae (L3). As a result, one type of microfilariae (i.e., long, slender and with uncoiled tail) developed in S. arakawae to the short L3 (478 μm long), while another type (short, thick and with a strongly coiled tail) developed to the elongate L3 (1, 100-1, 230 μm long) in two other Simulium species. Morphometric analysis of these L3 shows that the former type microfilariae are likely to include O. lienalis, whereas the latter represent an undescribed species, readily distinguishable from O. gutturosa and O. gibsoni so far reported from Japanese cattle.