Seasonal variation in gastrointestinal helminth infection of beef cows and effect of Ivermecthrin at different intervals

Foram utilizadas 55 vacas da raça nelore com idade entre cinco e oito anos, naturalmente infectadas por nematódeos gastrintestinais, divididas em cinco grupos de onze animais; um grupo permaneceu com controle, enquanto os outros foram tratados com Ivermectrin, na dose de 200 mcg/kgpv. O medicamento, aplicado em intervalos de 60, 75 e 90 dias, interferiu na carga parasitada subclínica dos animais, o que não ocorreu com o tratamento a cada 120 dias. Os resultados das culturas de fezes e das contagens de OPG, realizadas mensalmente, mostraram que não houve diferenças estatisticamente significativas entre a carga parasitária dos bovinos na estação seca e chuvosa; nas coproculturas, as larvas de Cooperia foram as mais frequentes, seguidas, respectivamente, das de Haemonchus, Oesophagostomum e Trichostrongylus.Fifty-five nellore cows with gastrointestinal nematode infections were divided into five groups of eleven animals each; one group was taken as the control, and to the ether four groups were given 200 mcg/kgbw of Ivermectin at intervals of 60, 75, 90 and 120 days throughout the year. The treatments one, two and three had some effect in the subclinic nematode gastrointestinal infections, while the treatment number 4 had no effect at all. Cooperia was the most frequent infective larvae found in the coprocultures, followed by Haemonchus, Oesophagostomum and Trichostrongylus larvae respectively. There were no differences in the worm burden between the dry and wet seasons