Pathogenicity of environmental origin salmonellas in specific pathogen-free chicks

Two hundred sixty 1-d-old specific pathogen-free (SPF), Single Comb White L eghorn chicks were used in this study to determine pathology caused by Salm onella enteritidis (SE) isolated from a poultry environment. The chicks wer e subdivided into 10 equal groups of 26 chicks each. Eight groups of chicks were inoculated individually with 0.5 mL of brain heart infusion broth cul ture containing 1 X 10(6) cfu of SE phage type (PT) -8 (1, 2, 3), SE PT5 A (1, 2), or SE PT4 (Ch-env-CA, chicken-CA, and human) by crop gavage. One gr oup of 26 chicks were inoculated with 1 X 10(6) cfu of Salmonella pullorum per bird by crop gavage. Another group of 26 chicks were kept as an uninocu lated control group. All the chicks were observed daily for clinical signs and mortality. Salmonella was reisolated from different organs at 7, 14, 21 , and 28 postinoculation (DPI). All of the chicks were weighed individually at each interval. Two chicks at random from each group were euthanised and necropsied at each DPI for gross pathology. Selected tissues were examined for histopathological changes at 7 and 14 DPI. Dead chicks were examined f or gross and histopathological lesions. Mortality rates were 30.7, 15.3, an d 7.6% in the groups inoculated with S. pullorum, SE PT5A, and SE PT4 (chic ken-CA), respectively. No mortality or clinical sign were observed in other treatment groups or in uninoculated control groups. Cecal pouches were fou nd to be the ideal organ for reisolation of Salmlonella at acute or chronic infection compared with other organs. Mean body weights were reduced to 1. 8 to 12.6% in inoculated groups compared with the uninoculated control grou p. The consistent gross and hispathological lesions were of peritonitis, pe rihepatitis, yolk sac infection, and enteritis. Subclinical Salmlonella inf ection identified in this study resulted in reduced body weights of inocula ted birds compared with uninoculated controls.