Rivera-Mujica, Ileana M.

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Detection of anthelmintic resistance of gastrointestinal nematodes infecting Senepol, Charbray*Senepol, and Charolais* Senepol heifers in Puerto Rico
(2014) Rivera-Mujica, Ileana M.; Ortiz-Colón, Guillermo; College of Agricultural Sciences; Jiménez Cabán, Esbal; Pagán Morales, Melvin; Latorre Acevedo, José R.; Department of Animal Science; Borges, Sonia
The effects of four anthelmintics on nematode fecal egg counts in beef heifers was determined. Senepol [n= 22] and crossbred [Charolais*Senepol and Charbray*Senepol; n= 17] heifers were distributed among treatments with: albendazole (Valbazen®), imidazothiazole (Levasole®), doramectin (Dectomax®) and ivermectin (Ivomec®). Egg counts per gram of feces (EPG) were determined before and after administration of the drugs in order to evaluate their efficacy. Participation in the experiment was limited to animals that presented an EPG ≥ 50 and those included were treated only once (day 0) with one of the anthelmintics. The EPG was monitored on days 0, 9, 15, 22, 29, 36, 43, 60 and 90 after treatment. Animals treated with Ivomec® presented an 86% reduction in nematode egg count, while Levasole® and Dectomax® reduced the FEC by 100% and Valbazen® by 98%. In conclusion, no resistance was detected against Levasole®, Dectomax® and Valbazen®, all of which achieved a nematode egg reduction ≥95%. On the other hand, these results suggest nematode resistance to Ivomec®.