The seasonal incidence of helminth parasites of cattle in the eastern Transvaal Lowveld.

Two helminth-free tracer calves were exposed to natural helminth infestation of a farm in the eastern Transvaal Lowveld for one month. On a nearby farm calves grazed with the herd for at least 3 months before slaughter so that the cumulative worm burden could be determined. The gastro-intestinal parasites increased markedly after rain. The major species and order or prevalence were: Cooperia pectinata, Cooperia punctata, Haemonchus placei and Oesophagostomum radiatum; minor species were Bunostomum phlebotomum, Trichostrongylus falculatus, Nematodirus helvetianus, Trichuris spp., Parafilaria bovicola and Paramphistomum spp. The highest worm burdens of Cooperia spp. on the first farm were between December and March and with the exception of O. radiatum, which had a peak in January, the other species reached peak worm burdens on the other farm in March.