Pathology and colonization of internal organs after experimental infection of broiler chickens with <em>Salmonella</em> Gallinarum through oral or intraperitoneal routes

Summary This paper describes pathological changes and the frequency of isolation of Salmonella enterica subsp. enterica serovar Gallinarum (O: 9, 12) from inter- nal organs in broiler chicks experimentally infected through oral or intrape- ritoneal routes. The experiment was conducted on 110 one-week-old chicks divided into three groups: the CR group (30 chicks) was kept uninfected and served as control, the OR group (40 chicks) was inoculated orally with Sal- monella Gallinarum (10 9 organisms/ml), and the IP group (40 chicks) was infected intraperitoneally with Salmonella Gallinarum (10 9 organisms/ml). Three birds from each group (dead or sacrificed) were observed at 3, 5, 7, 14, 21, 28, 35, and 42 days postinfection for evaluation of gross and histopatho- logical changes in visceral organs, and for frequency of isolation of Salmo- nella Gallinarum from internal organs. Gross and histopathological changes were compared between infected groups by measuring mean lesion scores. The gross and histopathological changes in visceral organs, although similar in both infected groups, were more severe and observed at earlier stages of infection and in more birds in the IP group. There was however no significant difference between the two infected groups in the frequency of isolation of Salmonella Gallinarum from internal organs, even in fecal sheddings. It was therefore concluded that the intraperitoneal route should be primarily consi- dered for inducing Salmonella Gallinarum infection in experimental trials.