A comparison between the effects of conventional and selective antiparasitic treatments on nematode parasites of horses from two management schemes.

Little information exists concerning the presence of nematode parasites of horses in South Africa. Limited studies are available which compare the parasites in horses originating from differing management schemes. The aim of the present study was to compare the nematode parasites of 2 groups of horses which had been managed differently. Group 1, chiefly Nooitgedacht adult ponies, consisted of cycling or early pregnancy mares. They were maintained chiefly on zero grazing, given supplemental feed and treated 4 times a year with antiparasitic remedies. The horses in Group 2 were mostly Thoroughbred adults which grazed on irrigated pastures daily and received antiparasitic remedies twice a year. The 2 groups were each divided into conventional and selective subgroups. The horses in the conventional subgroup were treated with antiparasitic remedies as they had been previously under the relevant management. The horses in the selective subgroup were treated with an antiparasiticide if the nematode egg count was greater than or equal to 300 eggs per gram of faeces. Faecal samples, collected monthly from all horses, were analysed for quantitative nematode egg counts and larval cultures for each of the 4 subgroups. Nematode eggs recovered included those of Parascaris equorum, Strongyloides and predominantly, strongyles. Faecal samples of foals were also examined for oocysts of coccidian parasites, but were negative. Differentiation of third-stage larvae (L3) from cultures, distinguished between cyathostome (or small strongyles) and Strongylus spp. Statistical analyses were performed on the total mean nematode egg counts for conventional and selective subgroups within each group of horses and subgroups for each month.(ABSTRACT TRUNCATED AT 250 WORDS)