Abstract

The present study aimed to investigate the incidence of Salmonella infection in diarrheic ducklings in Kafr El Sheikh Governorate, Egypt. A total of 100 samples were collected from ducklings suffered from diarrhea and mortality. Also, 50 litter samples were collected from duck farms. All specimens were collected under aseptic conditions for the isolation of Salmonella spp. The incidence of Salmonella was 7% in pooled samples from cecum, liver, spleen and gall bladder and 6% in litter samples. Ten strains of Salmonella spp. were serotyped, of which, S. Salamae (1 strain), S. Miami (2 strains), S. Kentucky (4 strains), S. Paratyphi (2 strain) and S. Magherafelt (1 strain) were detected. Susceptibility of Salmonella isolates to 10 antimicrobial agents showed that Salmonella isolates were highly sensitive to amikacin (100%), followed by trimethoprim/sulphamethoxazole and gentamicin (50%). While isolates showed the highest percentage of resistance to norfloxacin (90%), followed by ciprocin (70%), flumox (70%) and amoxicillin-clavulanic acid (70%). Virulence genes (invA, hilA, and fimA) were detected by PCR assay, all 10 Salmonella isolates showed positive results for three virulence genes, which gave specific amplicon at 284, 150, and 85 base pairs, respectively. Lethality test in five groups of three-day-old ducklings with different five isolated strains indicated a mortality rate ranged from 20-30 % in three isolates only. The most lethal strain S. Paratyphi A was chosen for further investigation as a pathogenicity test. IL-6 slightly decreased in the infected group in comparison to control. The results indicated that ducks infected with Salmonella spp. significantly showed lower RBCs, Hb, PCV, Phagocytic activity, phagocytic index, and serum albumin while, significantly had higher WBCs, neutrophil, lymphocyte, serum globulin, uric acid, creatinine, AST and ALT concentrations compared to non-infected. It could be concluded that Salmonella has hepatic and renal destructive effects and immunosuppressive effects.