Equine onchocerciasis in Queensland and the Northern Territory of Australia.

Investigations were conducted on the taxonomy, distribution in the carcase, pathology and transmission of Onchocerca spp. in equids from Queensland and the Northern Territory. Examination of small groups of horses and ponies revealed high infection rates with O. cervicalis, while lesser numbers were infected with O. gutturosa. O. reticulata was not found. Neither of the Australian species is likely to be of economic importance to the horsemeat industry. The findings support the belief that O. cervicalis is a pre-disposing factor in the aetiology of equine nuchal disease, most commonly seen clinically as fistulous withers. O. gutturosa is virtually non-pathogenic. Forcipomyia (Lasiohelea) townsvillensis, Austrosimulium pestilens and Culicoides victoriae are suggested as potential vectors, and it is unlikely that C. brevitarsis is involved.