Primer informe en México sobre la presencia de resistencia a ivermectina en bovinos infectados naturalmente con nematodos gastrointestinales

the aim of this work was to determine the presence of ivermectin anthelmintic resistance in gastrointestinal parasitic nematodes in young cattle naturally infected in the state of campeche, mexico. this research was performed based on a survey of sanitary management to 35 cattlemen for the selection of suspicious herds with anthelmintic resistance problems. calves from six to 12 months age were selected because no anthelmintic treatment had been given for at least 60 days and because they showed more than 200 eggs per gram of feces (epg) before treatment. two groups of calves from seven to 13 each were randomly chosen; control group received no treatment, and treated group received ivermectin at a dose of 0.2 mg per kg of body weight, subcutaneously. fourteen days after treatment, the epg number was determined and infective larvae genera were taxonomically identified. data were analyzed using reso program for anthelmintic resistance. the results indicated a concerning problem of ivermectin anthelmintic resistance in the evaluated cattle of five ranches with levels higher than 60%. the nematode genera identified before treatment were: cooperia spp, haemonchus spp and oesophagostomum sp, and after treatment cooperia spp still remained in five ranches, followed by oesophagostomum sp and haemonchus spp for two of the evaluated ranches. this research shows, for the first time in the state of campeche, anthelmintic resistance in young cattle, as well as presence of gastrointestinal nematodes resistant to ivermectin.