Abstract: In order to screen the suitable method of establishing host infection model of Salmonella Pullorum, the infection model was established by inoculating chicken embryos of different ages with different inoculation methods and different concentration of bacteria solution.90 SPF chicken embryos were randomly divided into 9 groups, 10 in each group, which were divided into A, B, C, D, E, F, G, H, I groups, group A was blank control group, and the other groups were model groups.In the model groups, different concentrations of Salmonella Pullorum C79-3(1×10³, 3×10³, 9×10³, 3×10⁵, 9×10⁵ CFU/mL) were inoculated on SPF chicken embryos of different ages (11 and 14 embryo ages) by air chamber inoculation and eggshell contact inoculation.After hatching, the chicks were reared in different cages according to groups, the clinical symptoms and death of chicks in each group were observed every 12 hours for 7 days.At the end of the observation period, autopsy observation, histopathological examination and isolation and identification of Salmonella Pullorum were performed on the dead and surviving chickens.The results showed that all the chicks in each model group performed obvious symptoms of pullorum and died, and compared with other model groups, group F inoculated with 9×10⁵ CFU/mL of C79-3 bacteria in 11 embryo age eggshell contact infection and H group inoculated with 3×10³ CFU/mL of C79-3 bacteria in 14 embryo age eggshell air chamber infection had higher rate of eggshell emergence, which could reach 80% and 90%, respectively, and the shelled chicks showed obvious characteristics of pullorum dysentery.Autopsy showed liver hemorrhage, cecum enlargement and yolk sac malabsorption.Histopathological sections showed varying degrees of injury to the liver, cecum and heart, with an incidence of 100% and 88.8%, respectively, and the positive rate of Salmonella Pullorum was 70% and 90%.This study showed that the two methods of inoculating 0.1 mL 9×10⁵ CFU/mL C79-3 bacteria in 11 embryo age eggshell contact infection and 0.1 mL 3×10³ CFU/mL C79-3 bacteria in 14 embryo age air chamber infection could be used to establish a stable host infection model of Salmonella Pullorum.

Key words: Salmonella Pullorum; chicken embryo; modeling method