Investigation of Culicoides (Diptera: Ceratopogonidae) in relation to the transmission of bovine Onchocerca and other filariae in central Kyushu, Japan.

In Kyushu, Japan, where a human case of zoonotic onchocerciasis was found, a survey was conducted to know if the bovine Onchocerca species of this region, O. gutturosa, O. lienalis and O. sp., which develop in local Simulium spp., were also transmitted by Culicoides. A total of 17,006 out of 42,582 females of eight Culicoides species captured by light-traps from May to November in 1989 and 1990 at two cattle sheds, one in Oita and one in Kumamoto, were dissected and examine for Onchocerca infection. Overall results showed that none of the species had filarial infections except 4 of 946 C. arakawae, an ornithophilic species, collected in Oita which harboured filarial larvae with a short tail, belonging to Lemdaninae. Unsheathed microfilariae indistinguishable from O. lienalis or O. gutturosa were found in the midgut of only one blood-fed C. matsuzawai collected in Oita. It is concluded that Culicoides species would not be vectors of these three bovine Onchocerca species. Additional collections of Culicoides in a residential area of Oita showed that several filarial species, Lemdaninae and Splendidofilarinae, probably from birds, are transmitted by C. arakawae.