Anthelmintics and emergence of anthelmintic resistant nematodes in sheep: need of an integrated nematode management

Sheep are an important component of livestock in terms of the various direct and indirect benefits human beings derive from them. However, various species of gastrointestinal nematodes (GIN) parasitize sheep and affect their productivity worldwide. The principal mode of control of GIN is based on chemical anthelmintics (CA) because it is simple, cheap and offers both therapeutic and prophylactic cover against GIN. But, due to the emergence of anthelmintic resistant nematodes (ARN) against CA, the problem has become complicated. ARN have been recognised as an important threat to the productivity and welfare of sheep and numerous studies have been conducted worldwide in this direction. However, anthelmintic resistance (AR) has not been systematically investigated in Indian region and barring a few reports, there seems to be no authentic work on the prevalence of AR in sheep and/or other livestock sector. Plant anthelmintics (PA) are a promising alternative for GIN control and are a viable option for timely minimising and delaying the onset and development of AR in sheep. Therefore, an integration of various aspects of AR, search for alternative control like PA and emergence of new GIN diseases due to climate change poses a new question to formulate a comprehensive policy for integrated nematode management for efficient rearing and welfare of sheep. This paper is a critical overview in this direction to understand the problem and will serve as a template for consideration of AR at the academic, research, husbandry, industrial and at policy making level.