Resistência de parasitas gastrointestinais em ovelhas Texel no município de Dom Pedrito - RS

Abstract

The ovine verminosis is caused by infections of gastrointestinal parasites, which affects livestock performance, by affecting it in numbers and in quality, leading to the death of animals with high levels of parasitic infestations. The constant use of anthelmintics for verminosis control led to the development of resistant strains, resulting in the loss of effectiveness of the existing drugs. So that today there are just a few anthelmintics on the market capable of combating gastrointestinal parasites. This study aimed to evaluate the effectiveness of three different anthelmintics, commonly used in farms, in ewes of the Texel breed in Dom Pedrito-RS, Brazil. Sixty female sheep of Texel breed were used, divided into 4 experimental groups. Group 1 received Oxfendazole, Group 2 Ivermectin, Group 3 Disophenol and Group 4 received no treatment, being considered the control group. The feces were harvested directly from the rectum of the animal before application of the drug (day 0). Another harvesting was carried out 14 days after application of anthelmintics. For efficacy testing and identification of the parasites, the samples were analyzed by quantification of eggs per gram of feces (EPG) and stool cultures. Data analysis was performed using the procedure PROC GLM of the software SAS, by Tukey test, with a level of 5% of significance. As a result of the stool culture gastrointestinal parasites such as Haemonchus sp, Oesophagostomum sp, Ostertagia sp., Strongyloides and Trichostrongylus sp. were found, with an initial variability of 79%, 2%, 3%, 5% and 11%, respectively. For the parasitic resistance results it was observed an anthelmintic efficacy of 90.4% in the treatment with Oxfendazole, -29.8% in the one with Ivermectin, 78.4% in the one with Disophenol and 67.9% in the control. However it was not enough, as it is necessary to have a 95% efficiency in order to not be considered resistant. So, it was observed resistance to all anthelmintics used. When comparing the pretreatment EPG means with the post treatment EPG means, only the treatment 2 showed no differences. There was no efficacy in the treatments used to control of verminosis in sheep.