Pathogenicity of Salmonella enteritidis phage types 4, 8 and 23 in specific pathogen free chicks

The pathogenicity of two isolates of Salmonella enterica serovar Enteritidi s (SE) phage type (PT) 4, three of PT8 and one of PT23 was investigated in groups of 1-day-old specific pathogen free White Leghorn chicks. Two groups were crop gavaged with each culture but at two different doses. Two additi onal groups were given Salmonella enterica serovar Pullorum (SP) at similar doses and one further group served as uninoculated controls. Body weights were recorded at 14, 21, and 28 days postinoculation (d.p.i), and mortality was monitored throughout. In most treatment groups, the average body weigh ts were significantly lower than the controls. Birds inoculated with SP had the highest mortality followed by those given SE PT4 of human or chicken o rigin. At 14 and 21 d.p.i., four chicks from each group were killed and exa mined for gross lesions. Selected tissues were collected for histopathology and cultured for bacteria. Dead birds had fibrinous exudate in the pericar dium and also, in a few, on the liver capsule. They had enlarged livers, so metimes with congestion and white foci. At 7 d.p.i., several birds, especia lly those inoculated with SE PT4, had retained yolk sacs containing coagula ted material. Microscopic lesions of pericarditis, myocarditis, hepatitis, splenitis, peritonitis and enteritis were present at 7 d.p.i. in most birds inoculated with SE, but was greatly variable at 14 d.p.i.. This study show s that 1-day-old SPF chicks are susceptible to various phage types of SE, w ith yolk-sac infection as the most prominent feature.