Managing anthelmintic resistance in small ruminant livestock of resource-poor farmers in South Africa : review article

Abstract

Gastrointestinal parasitism is one of the most important disease complexes of sheep and goats impacting on the resource-poor livestock farmer. Of the responsible nematodes, Haemonchus contortus, a blood-sucking worm of the abomasum, poses possibly the greatest threat. Over the past several decades, the worm has been controlled through the use of anthelmintics, but the emergence of anthelmintic resistance has threatened this chemotherapeutic approach. In Africa, the overall prevalence of anthelmintic resistance has not been extensively investigated, particularly within the resource-poor farming sector, but resistance has been reported from at least 14 countries with most of the reports emanating from Kenya and South Africa and the majority concerning H. contortus. While levels of resistance under commercial sheep farming systems in South Africa is considered to be amongst the worst in the world, resistance has also been reported from the resource-poor farming sector. Increases in productivity and reproduction of livestock and the development of markets for sale of animals are seen by international funding bodies as a way out of poverty for communities that keep livestock. This must lead to the greater need for parasite control. At such times, the risk of levels of anthelmintic resistance escalating is much greater and there is therefore a need to look at alternatives to their use. Proposed strategies include the appropriate, but judicious use of anthelmintics by application of the FAMACHA(c) system and the use of alternatives to anthelmintics such as strategic nutrient supplementation. It is also very clear that there is a strong demand for knowledge about animal diseases, including helminthosis, and their effective management in the resource-poor livestock farming communities. This is an important challenge to meet.