First report of Benzimidazole resistance in equid intestinal strongyles from Kashmir valley, India

Benzimidazole (BZ) anthelmintics have been used indiscriminately in equids to control nematode infections throughout the world including India and has led to the development of BZ resistance. In order to determine the current status of BZ resistance in equids of Kashmir against intestinal strongyles (IS), the present study was conducted using faecal egg count reduction test (FECRT) and Allele specific PCR (AS-PCR). The study was conducted on ponies from three major tourist destinations of Kashmir viz; Gulmarg, Pahalgam and Sonamarg in accordance with the WAAVP guidelines. The animals which were selected for FECRT at each location received treatment with albendazole at 5 mg/kg b.wt. FECRT revealed BZ resistance in IS at 2 locations viz; Gulmarg [95.71% FECR; 92.4 & 98.2% CI (90% lower & upper confidence intervals, respectively)] and Pahalgam (64.49% FECR; 18.8 & 92.7% CI), whereas it was inconclusive at Sonamarg area (91.29% FECR; 76.9 & 99.1% CI). AS-PCR was conducted on genomic DNA isolated from cyathostome larvae harvested from pooled faecal samples of pre-treatment cultures each at Gulmarg, Pahalgam and Sonamarg. A total of 211 larvae of cyathostomes were genotyped, out of which 4.74%, 74.88% and 20.38% were homozygous resistant (rr), homozygous susceptible (SS) and heterozygous (rS), respectively. Homozygous resistant larvae (rr) were found only at Pahalgam (16.39%). Overall frequency of resistant allele (r) was less (0.15) than suceptible allele (S) (0.85). It is concluded that there is evidence of development of BZ resistance by IS of equids in Kashmir and as such it is recommended that appropriate scientific measures must be taken to mitigate it.