The authors present a clinical case in a herd of one thousand sheep, whose presumptive diagnosis made by the farmer's assistant veterinarian, was paratuberculosis. Biochemical, pathological, serological, bacteriological, virological and parasitological tests, were done on some animals that presented with the most extensive clinical symptoms. The obtained results led us to conclude that the first presumptive diagnosis wasn't confirmed. All symptoms and lesions were due to a strong parasitic infection caused by Moniezia expansa and Dictyocaulus filaria.