Survey on anthelmintic resistance to gastrointestinal nematodes in unorganized goat farms of Tamil Nadu.

One of the major problems in small ruminant farms is emergence of anthelmintic resistance (AR) to commonly used dewormers. This study investigated AR to gastrointestinal nematodes affecting goats in 27 unorganized farms in three different agro-climatic zones (Cauvery delta zone, high altitude zone and high rainfall zone) of Tamil Nadu, India. Two anthelmintics viz., albendazole (AZ) and levamisole (LEV) were used in this study as per the dose recommended by the manufacturer. Status of AR was detected by using the faecal egg count reduction test. Results revealed the presence of high level of resistance to both AZ and LEV. In the high rainfall and high altitude zones, all the farm flocks were found to be resistant to LEV. In the Cauvery delta zone, 13 farm flocks were resistant and four farm flocks showed suspect resistance to AZ. Fifteen farm flocks showed resistance and two showed suspect resistance to LEV. Further, morphological characterization of the infective larvae derived from faecal cultures indicated that by far the most predominant gastrointestinal nematode species found in goats was Haemonchus contortus.