© 2016 JETIR November 2016, Volume 3, Issue 10 www.jetir.org (ISSN-2349-5162) JETIR1701164 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 809 CHALLENGES IN THE CONTROL OF NEMATODIASIS IN SMALL RUMINANTS: A REVIEW A. Varadharajan and R. Gnanasekar Division of Animal Husbandry, Faculty of Agriculture, Annamalai University, Annamalai Nagar – 608 002. Tamil Nadu, India. ABSTRACT Out of various diseases affecting sheep, parasitic gastroenteritis caused by gastro-intestinal nematodes, mainly Haemonchus contortus, is very important for the sheep in India and is responsible for high mortality and morbidity (Yadav, 1997). The gastrointestinal nematodes of sheep include H. contortus, Telodorsagia circumcinta, Trichostrongylus axei, Nematodirus spp. and Cooperia spp. The proportions of each of these nematodes in sheep populations vary according to geographic location. H. contortus and T. circumcincta represent most of the parasite burdens seen in sheep, with H. contortus being present in highest numbers. Anthelmintic resistance is present in all of these parasites, but the prevalence is highest for H. contortus, making it the most economically important gastrointestinal nematodes of sheep (Fleming et al., 2006). Keywords: Animal health, Anthelmintic resistance, Gastrointestinal nematodes, Small ruminants, Livestock productivity INTRODUCTION Small ruminants are important source of income for rural communities whose livelihood is largely based on livestock production (Biffa et al., 2006). Sheep is an important livestock species in India. India is a rich source of diverse ovine germplasm with 74 million sheep which is 6.8% of the world’s sheep population (FAOSTAT, 2010). They contribute greatly to the agrarian economy especially where crop and/dairy farming are not economical. They play an important role in the livelihood of a large percentage of small and marginal farmers and landless labours engaged in sheep rearing. However, sheep production is hindered by many factors including animal health constraints, inadequate nutrition and poor husbandry system (Sissay et al., 2006). USE OF ANTHELMINTICS AGAINST GASTROINTESTINAL NEMATODIASIS In most cases, Haemonchus contortus was the first nematode to develop resistance against the different anthelmintics (Fleming et al., 2006). There is substantial evidence that when a parasite has developed resistance to one anthelmintic from a certain class, it will usually also be resistant to other products from the same class. There is also evidence that strategic treatments have contributed to resistance development, particularly at times when the free-living component of the parasite population has been small. The most efficient way to limit the increase of anthelmintic resistance remains the reduction of the selection pressure by drugs and optimal timing to maximise their efficacy (Silvestre et al., 2002). Gastrointestinal nematodes in grazing animals cause major production losses and represent an animal welfare problem worldwide. For decades, use of anthelmintics has been central in the control programmes of these parasites, as this is the only practical method to reduce the adverse effects of these nematode parasites. There are only three broad-spectrum anthelmintic classes available for treatment and control of nematodes, namely benzimidazole, imidathiazole and macrocyclic lactones. No new class with different mode of action is expected in the market in near future, as development and release of new anthelmintic may take 6 –8 years and