The incidence of helminths in pigs, sheep, cattle, impala and blesbok in the Transvaal.
The seasonal fluctuations in the worm burdens of pigs, sheep, cattle, impala and blesbok exposed to infestation on improved or natural pastures in the Transvaal were determined. The prevalence of infestation in pigs slaughtered at the Pretoria Municipal Abattoir and in impala near Pafuri and blesbok at Badplaas was also established. Sheep, goats and cattle were successfully artificially infested with a number of nematodes of impala origin and sheep with those of blesbok origin. The various methods used to determine the seasonal incidence of helminth parasites are discussed and the wastage of valuable material criticised when complete recoveries of both internal and external parasites are not attempted at each necropsy. Host specificity and the distribution of parasites according to climate and the zoogeographical distribution of their hosts are discussed and the epizootiology of the major nematode genera parasitizing sheep, cattle, impala and blesbok in the Transvaal is determined. The phenomenon of arrested development in nematodes is compared with that of diapause in insects and measures to control helminth parasites 1n domestic stock and antelope in the Transvaal are suggested.