A COMPARISON BETWEEN THE EFFECTS OF CONVENTIONAL AND SELECTIVE ANTIPARASITIC TREATMENTS ON NEMATODE PARASITES OF HORSES FROM 2 MANAGEMENT SCHEMES

Little information exists concerning the presence of nematode parasite s of horses in South Africa. Limited studies are available which compa re the parasites in horses originating from differing management schem es. The aim of the present study was to compare the nematode parasites of 2 groups of horses which had been managed differently. Group 1, ch iefly Nooitgedacht adult ponies, consisted of cycling or early pregnan cy mares. They were maintained chiefly on zero grazing, given suppleme ntal feed and treated 4 times a year with antiparasitic remedies. The horses in Group 2 were mostly Thoroughbred adults which grazed on irri gated pastures daily and received antiparasitic remedies twice a year. The 2 groups were each divided into conventional and selective subgro ups. The horses in the conventional subgroup were treated with antipar asitic remedies as they had been previously under the relevant managem ent. The horses in the selective subgroup were treated with an antipar asiticide if the nematode egg count was greater than or equal to 300 e ggs per gram of faeces. Faecal samples, collected monthly from all hor ses, were analysed for quantitative nematode egg counts and larval cul tures for each of the 4 subgroups. Nematode eggs recovered included th ose 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 (L 3) from cultures, distinguished between cyathostome (or small strongyl es) and Strongylus spp. Statistical analyses were performed on the tot al mean nematode egg counts for conventional and selective subgroups w ithin each group of horses and subgroups for each month. Differences b etween treatment subgroups were statistically significant in Group 1 b ut not in Group 2. Considering that the numbers and costs of laborator y tests were constant for all subgroups, a considerable financial savi ng was realised for the selective subgroup compared to the conventiona l, particularly in Group 1. In addition to the financial advantages, a nother benefit is the avoidance of further development of resistance t o the antiparasitic remedies. Finally, a selective proramme of control can be developed with basic management which includes monitoring of n ematode parasite levels through faecal examination, prior to treatment with appropriate antiparasitic remedies.