[Characterization of Teladorsagia circumcincta and T. trifurcata. I. Epidemiological and biological aspects].

The natural infections of sheep were studied in six biotopes, in order to determine periods, biotopes and type of sheep at risk. Experimental infections were realized in order to assess the fertility of both Teladorsagia. T. trifurcata was more frequent in autumn and spring, among lambs and in biotopes where the climate was not contrasted. T. trifurcata produced more eggs/female then T. circumcincta.