Resistência de Haemonchus placei (PLACE, 1893), Cooperia punctata (von LINSTOW, 1907) E Oesophagostomum radiatum (RUDOLPHI, 1803) às avermectinas em bovinos, em propriedade rural de Minas Gerais

Abstract

Using controlled test with artificial infection. Forty-eight calves helminth free were infected individually with 11,000 L3 of Cooperia sp., 11,000 of L3 Haemonchus sp. and 48,000 L3 of Oesophagostomum sp. Groups were formed with 12 animals each: T1 - control group, T2 -group treated with Dectomax 1%, T3 - group treated with ivermectin 3.15% and T4 - group treated with a combination of ivermectin 2.25% plus abamectin 1.25%. On the infection day and 46 days after it, haematological parameter were evaluated. To evaluate the effectivenesspersistence, six animals from each group were necropsied 14 days after the treatments, the rest of the animals were necropsied 28 days after the treatments in order to have the helminth counts. There was no change in total leukocytes, monocyte, lymphocytes and band neutrophilsbetween evaluations. Eosinophils and segmented neutrophils suffered slight decrease in values with statistical difference, but within the bounds of normality. On 46th day the globular average and the average plasma figures below the lower limit of normality and showed significantdecrease during the experiment. In controlled test the effectiveness 14 days after treatment, calculated using the arithmetic mean of helminth counts were T2 - 80%, 66% and 39%, T3 - 40%, 18% and 52% and T4 - 74% , 97% and 95% for Haemonchus placei, Cooperia punctataand Oesophagostomum radiatum. The effectiveness calculated 28 days after the treatment was T2 - 18%, 25% and 0%; T3 - 0%, 52% and 0% and T4 - 89%, 98% and 86%. Thus, isolated from Haemonchus placei were identified as resistant to drugs in this experiment. Isolated fromCooperia punctata and Oesophagostomum radiatum were identified as resistant to doramectin 1%, ivermectin 3.15% and sensitive to the association of ivermectin 2.25% 1.25% plus abamectin