Experimental listeriosis in chickens: microbiological and anatomo-histopathological studies and health and hygiene considerations

The authors report the results of an experimental infection of 20 chickens with L.m. in order to verify if they became affected by Listeriosis and to individuate the degree of contamination of the meat and parenchymas and eggs. Despite the high infecting dose (160 x 10(7) micro-organism in group 1, 51 x 10(8) + cortisone in group 2, 130 x 10(8) in group 3), no signs of the disease were found in any of the animals; besides, L.m. was isolated in the faeces of only 3 subjects for 1 day post-infection and in the organs of 4 subjects for a maximum of 15 days post-infection. From a histopathological point of view only simple lymphocytic-macrophagic and eosinophilic proliferations localized in the liver and, to a lesser extent, in other parenchymas were observed. The authors advance the hypothesis that the frequent isolations of L.m. in chicken meat and eggs can be attributed to exogenous contamination in stages of slaughtering and marketing of the product.