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Diagnosis and prophylaxis of oestrosis in sheep


Not all sheep parasitized by Oestrus ovis show clinical signs, which precludes the precise determination of oestrosis incidence. For this reason, accurate diagnosis requires detection of larvae during necropsy. From a scientific point of view, this is a limiting factor in experiments designed to determine the prevalence of parasitism or in evaluating the effectiveness of antiparasitics against oestrosis. For this reason, it is necessary to use more accurate methods for diagnosis. Then, PCR ("Polymerase Chain Reaction") will be evaluated to identify O. ovis DNA in order to perform the diagnosis of oestrosis. The trial will also aim to evaluate the efficacy of Closantel and Ivermectin in the prophylaxis of oestrosis and productive performance of 30 lambs submitted to natural O. ovis infestation and distributed into three groups: (1) treated with Closantel; (2) treated with Ivermectin and (3) control without treatment. The animals will be treated twice 60 days apart and will be euthanized 30 days after the second treatment, to recover and quantify the different larval instars of O. ovis, as well as the gastrointestinal helminths. Biweekly, samples will be taken for coproparasitological and hematological examinations, as well as plasma, to be used in the determination of the levels of IgG anti-O. ovis by the ELISA method. The animals will be weighed and clinical signs of Oestrosis will be recorded individually. For molecular analysis, nasal secretion samples will be collected from all animals at five occasions: on treatment days, seven days after treatments and on euthanasia. DNA extracted from these samples will be subjected to a semi-nested PCR protocol to amplify a hypervariable fragment (~ 300 bp) in the Oestrus COX 1 gene. (AU)

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