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

Benzimidazole resistance in intestinal strongyles of equids has been detected for the first time in the Kashmir valley, India, using fecal egg count reduction tests and genetic analysis. This study highlights emerging parasite drug resistance in horses that requires attention to manage effectively.

Background and Purpose

• Benzimidazole (BZ) drugs have been widely used to treat nematode infections in horses globally and in India.
• Frequent and indiscriminate use of BZ anthelmintics leads to resistance development in intestinal strongyles, common equid parasites.
• The study aims to assess the current status of BZ resistance in intestinal strongyles infecting ponies in major tourist locations of Kashmir: Gulmarg, Pahalgam, and Sonamarg.
• The research follows WAAVP (World Association for the Advancement of Veterinary Parasitology) guidelines which standardize anthelmintic efficacy testing.

Methods

• Fecal Egg Count Reduction Test (FECRT): Evaluates drug efficacy by measuring parasite egg reductions in feces after treatment with albendazole at 5 mg/kg body weight.
• Allele-Specific PCR (AS-PCR): A molecular technique used to detect the presence of resistance-associated alleles in parasite DNA.
• Samples were collected from ponies at the three locations pre- and post-treatment for FECRT and for larval DNA extraction for AS-PCR.
• A total of 211 cyathostome larvae were genotyped via AS-PCR to determine the genotype frequencies of resistant (rr), susceptible (SS), and heterozygous (rS) alleles.

Key Findings

• FECRT Results:
• Gulmarg: 95.71% reduction (Confidence Interval 90% lower: 92.4%, upper: 98.2%) indicating developing resistance.
• Pahalgam: 64.49% reduction (CI 18.8% – 92.7%) signaling clear resistance.
• Sonamarg: 91.29% reduction (CI 76.9% – 99.1%) which was inconclusive regarding resistance.
• AS-PCR Genotyping:
• From 211 larvae genotyped: 4.74% were homozygous resistant (rr), 74.88% homozygous susceptible (SS), and 20.38% heterozygous (rS).
• Homozygous resistant larvae were exclusively found at Pahalgam (16.39%).
• Resistant allele (r) frequency was 0.15 while susceptible allele (S) frequency was 0.85 overall.

Interpretation and Implications

• The coexistence of homozygous resistant genotypes and reduced efficacy of albendazole points to the emergence of benzimidazole resistance among intestinal strongyles in equids from Kashmir.
• The varying resistance levels among sites suggest localized differences in drug pressure or parasite population genetics.
• Presence of heterozygotes indicates ongoing genetic mixing and possible spread of resistance alleles.
• This is the first documented report from Kashmir valley, highlighting a need for immediate attention towards resistance management in equid parasite control programs.

Recommendations

• Implement integrated parasite management strategies to minimize further resistance development.
• Regular monitoring of anthelmintic efficacy using FECRT and molecular tools to track resistance trends.
• Consider alternative anthelmintic classes and rotation schemes rather than continuous BZ use.
• Educate equid caretakers and veterinarians on responsible anthelmintic use and the risks of resistance.