A Study on the Pathological and Bacterial Shedding of 9R <i>Salmonella gallinarum</i> and <i>Salmonella pullorum</i> Killed Vaccine in Layer Hens

This study aimed to evaluate the effectiveness of immunization of the 9R Salmonella gallinarum strain and killed Salmonella Pullorum vaccine in protecting layer chickens from Salmonella pullorum infection. 60 chickens were divided into three groups: one group received the 9R vaccine; the other received the killed Salmonella pullorum vaccine, and the third group the control negative. after challenge revealed that the group vaccinated with the killed vaccine (G2) noticed slight histopathological changes, represented by moderate MNCs infiltration with heterophils whereas the group that received the live vaccine (G1) showed moderate multiple MNCs infiltration and mild sinusoidal congestion with the prominence of Kupffer cells compared to the third group, which showed focal MNCs infiltration forming granulomatous lesion with sinusoids dilation and congestion. In conclusion, the killed vaccine has an important role in protection against challenges with S. pullorum in comparison with the live vaccine (9R), without bacterial shedding, low morbidity without mortality and less histological changes.