THE EPIDEMIOLOGY OF GASTROINTESTINAL NEMATODE INFECTIONS IN COMMUNAL CATTLE AND COMMERCIAL BEEF-CATTLE ON THE HIGHVELD OF ZIMBABWE

An epidemiological study of gastrointestinal nematode infections of ca ttle was conducted on the highveld of Zimbabwe from June 1993 to May 1 995. The study was carried out in two communal areas, two conventional beef farms and two commercial beef farms with irrigated pastures. On all farms/areas, faecal egg counts were low (< 500 eggs per g faeces) during the dry season, During the rainy season faecal egg counts were highest in communal areas and lowest in conventional beef farms. Those of irrigated farms had intermediate values. During the dry season pas ture larval counts were low in irrigated pastures and conventional bee f farms and virtually zero in communal areas. They increased and peake d during the rainy season, coinciding with the egg count peaks. Worm b urdens of necropsied cattle indicated that 100% of the animals were in fected with nematodes, The important species were Cooperia pectinata, C, punctata, Haemonchus placei, Trichostrongylus axei and Oesophagosto mum radiatum in all farms/areas and Ostertagia osterragi in a beef far m with irrigated pastures, Haemonchus survived the dry season as inhib ited early fourth stage larvae whereas Cooperia and Trichostrongylus s urvived as adults.