- The study investigated the prevalence of gastrointestinal nematodes resistant to common dewormers (albendazole sulfoxide, ivermectin, and levamisole) in hair-sheep farms across Campeche and Yucatán, Mexico, from 2016 to 2019, using the faecal egg count reduction test (FECRT).
- The farms surveyed had more than 100 grazing ewes, and resistance was measured using three different formulae that estimated the percentage reduction in parasite eggs post-treatment.
- Results indicated high resistance rates to ivermectin (up to 100% in some areas), consistent findings for albendazole sulfoxide, while levamisole resistance showed some variability depending on the