A review of the literature on onchocerciasis of animals is presented. Aspects covered include geographic distribution, host range, taxonomy, pathology, public health, transmission, treatment and control.
Three species of Onchocerca are described from Australian cattle: O. gibsoni, O. gutturosa and O. lienalis. The most reliable taxonomic features used in identification are the female cuticle and tail. The validity of O. stilesi (Eberhard 1979) as a species distinct from O. lienalis is questioned. A technique of identifying microfilariae based on variations in the shape of the cuticular striae is described. Morphological differences between L3 larvae which are of potential taxonomic significance are described.
The distributions of the adults of the three bovine species in the carcase, and of the microfilariae in the skin, are described. The main infection sites for the adults and microfilariae respectively of each species are the brisket and navel fold for O. gibsoni,the ligamentum nuchae and the withers for O. gutturosa and the gastro-splenic ligament and the loin for O. lienalis. The potential economic importance of these infections is discussed.
The uptake of microfilariae by Forcipomyia (Lasiohelea) townsvillensis and Culicoides marksi is recorded. C. brevitarsis, a species which several workers have considered to be a potential vector, was not observed to take up microfilariae. The biting behaviour of F. (L.) townsvillensis in relation to the transmission of bovine onchocerciasis and the subsequent development of presumed O. gutturosa larvae to the infective stage are described. The laboratory transmission of O. gibsoni to cattle, using L3 larvae from F. (L.) townsvillensis is described.
Equine onchocerciasis involving O. cervicalis and O. gutturosa is reported on. Taxonomy, carcase distribution and microfilarial distribution are briefly discussed. O. reticulata does not appear to occur in Australia. Strong evidence of the possible role of O. cervicalis as a predisposing factor to the development of clinical equine nuchal disease (fistulous withers) is presented. Possible vectors, including Austrosimulium pestilens, Culicoides marksi, and F. (L.) townsvillensis are discussed.
Onchocerciasis of buffaloes, camels, sheep and goats is discussed briefly. O. gutturosa was recovered from water buffalo, and O. gibsoni from sheep. O. fasciata does not appear to have become established in Australian camels.
The current state of knowledge about animal onchocerciasis is discussed, and future avenues of research suggested. The significance of Forcipomyia (Lasiohelea) townsvillensis in the transmission of animal, human and zoonotic onchocerciasis in Australia is discussed.