Resistencia a los antihelmínticos en nematodos gastrointestinales de bovinos en municipios de Cundinamarca y Boyacá

A study was conducted in 36 farms of the Bogota Savannah, Ubate and Chiquinquira Valleys and Tequendama Region (Cundinamarca), to determine via in vivo egg reduction count test (ERCT) antihelmintics resistance to bovine gastrointestinal nematodes. Resistance was determined in. 40 calves, three to 12 months of age, allotted to four groups of ten animals each one: 1) control (untreated); 2) albendazol 25% (5 mg/kg); 3) ivermectin 1% (0.2 mg/kg) and 4) levamisol 18.8% (1 mg/kg). By feces cultivation techniques, six genera were identified, Cooperia spp. being the predominant one. Resistance was determined when the ERCT was below 95% and the lowest 95% confidence interval limit was 90. Resistance was found in 25% of the farms: albendazol and ivermectin resistance was detected in 17% and 8% of the farms, respectively. Cooperia spp. was involved in both compounds. Average egg per gram (epg) of feces reduction after treatments with ivermectin, albendazol and levamisol, was 97.89% ± 6% (66% - 100%); 95.9% ± 9.3% (51% - 100%) and 99.4% ± 0.92% (97.6 - 100%), respectively. Resistance to levamisol was not detected. Risk factors associated with resistance were: worming of adult cattle, wrong dosage regarding body weight and use of the same active ingredient for more than four years.