Seroprevalence and pathological studies of Salmonella infection in commercial white layer birds

The present study was conducted to determine the seroprevalence and pathology of Salmonella infection in white commercial layer birds of District Faisalabad during June 2018 and June 2020. The current study aimed to determine the isolation, identification of Salmonella gallinarum (S. gallinarum), its cultural prevalence, antimicrobial resistance, molecular characterization, and pathological lesions produced in different organs of commercial layer birds. Initial screening of poultry flocks was done through serum plate agglutination test followed by culturing in different media, motility test, molecular confirmation, and histopathology. Based on the serum plate agglutination test, seroprevalence in the commercial white layer in dead and live flocks was 40.09%. The cultural prevalence of Salmonella in the seropositive group was 75.36% and in the seronegative was 31.84%. Cultural prevalence in the liver of dead birds was 62.06%, in spleen 58.62%, and in cloacal swabs was 67.24%. A total of 178 isolates were characterized through cultural characteristic and motility tests, among them 63.48% isolates were S. gallinarum, and 36.51% isolates were S. pullorum. The antibiogram study revealed that all the tested isolates were resistant to amoxicillin, gentamycin, kanamycin, doxycyclin, and tetracyclin. While tested isolates were sensitive to ciprofloxacin against S. gallinarum. Pathologically liver was friable, showing bonze discoloration with focal necrosis, enteritis of various grades, mottled white spleen, and enlarged kidneys were found. Microscopically, leukocytic infiltration with focal necrosis and degeneration, in mucosa and submucosa of intestinal inflammatory cells were observed. In conclusion, the seroprevalence, antibiogram, and molecular characterization of Salmonella help to control the disease in a better way through bacterin production of local isolates.