[Experimental paratuberculosis in sheep after intravenous or oral inoculation: pathogenicity and biologic diagnosis].

Abstract

An experimental paratuberculosis study was performed in sheep. One group of 6 lambs was inoculated intravenously with the equivalent of 50 mg (wet weight) of live bacilli, another group of 6 lambs was inoculated orally by placing 500 mg (wet weight) of live organisms in milk feed and a group of 3 lambs was used as controls. The degree of cellular immunity was followed by examining delayed hypersensitivity using 3 allergens (bovine tuberculin PPD, avian tuberculin PPD and johnine PPD) and that of humoral immunity using complement fixation test, agar gel immunodiffusion test and ELISA. The elimination of bacilli in the faeces was examined simultaneously. After 2 years no macroscopic or microscopic lesion was observed in intravenously inoculated lambs and in those exposed orally to M paratuberculosis; cultures were negative. It appears that domestic sheep were able to control the infection. Nevertheless, most of them developed cellular and humoral immunity against paratuberculosis antigen. The best results were obtained in intravenously inoculated lambs.