Resistance of Haemonchus, Cooperia, Trichostrongylus, and Oesophagostomum to ivermectin in dairy cattle in Paraná

Abstract

The objective of this study was to analyze the effect of ivermectin (3.15%) on gastrointestinal nematodes found in calves through the fecal egg count reduction test (FECRT), and larval culture in 16 animals from a school farm at the Universidade Estadual do Norte do Paraná. The animals were divided into two experimental groups: animals treated with ivermectin 3.15% (G1 group) and control animals (G2 group). Stool samples were collected from the animals twice i.e., on days 0 and 10 for fecal examinations. There was no significant change in the egg count per gram of feces (EPG) in both the groups. Helminths were found to be resistant to ivermectin (3.15%), due to the observed 5.62% FECRT rate. Cooperia was found to be the dominant nematode larvae present (53% on day 10 day and 8% in day 0), while Trichostrongylus was detected in small numbers (0% on day 0 to 1 % on day 10). The drug was found to be effective only in Trichuris, while the same was inefficient against Haemonchus and Cooperia, although Trichostrongylus and Oesophagostomum were found to be 100 % resistant. Therefore, the findings of this study suggest that ivermectin 3.15% should not be used for the control of nematodes in calves, since most of the parasites demonstrated drug resistance. This is the first report on the resistance of Haemonchus, Cooperia, Trichostrongylus, and Oesophagostomum in cattle to ivermectin 3.15% in the state of Paraná.