Pathogenicity and persistence of Salmonella enteritidis and egg contamination in normal and infectious bursal disease virus-infected leghorn chicks

The pathogenicity and persistence of Salmonella enteritidis (SE) phage type 8 and resulting egg contamination in normal and infectious bursal disease virus (IBDV)-infected white leghorn chicks were evaluated over 34 weeks and in some birds over a 64-week period. Four hundred 1-day-old specific-pathogen-free (SPF) straight-run white-leghorn chickens were allotted into four treatment groups: negative control, IBDV infected, IBDV+SE-infected, and SE-infected. Chicks were infected with IBDV at 1 day of age and with SE phage type 8 at 2 days of age. SE persisted in the gut of more than 50% of the chicks of both SE-infected groups through 34 weeks postinoculation (PI), and SE could still be isolated from cloacal/rectal swabs taken at 64 weeks. IBDV+SE-infected chicks had severe gross lesions and significantly (P < 0.001) higher mortality (32%) than the negative control (1%), IBDV-infected (10%), and SE-infected (1%) groups. Gross lesions consisting of fibrinous pericarditis, perihepatitis, peritonitis, airsacculitis, and inspissated yolk were observed only in the IBDV+SE-infected group. SE isolations from internal organs of chickens in the IBDV+SE infected group decreased from 83% at 8 weeks to 0% at 14 weeks PI; isolations from the SE-infected group decreased from 50% at 8 weeks to 0% at 10 weeks PI. Salmonella isolations increased from 0% to 14% in both groups at 18 weeks, corresponding with the time of sexual maturity. Of the 1,050 eggs cultured from the IBDV+SE-infected group, SE was isolated from 88 shells, five albumens, and two yolks. In contrast, of 1,258 eggs from the SE-infected group, 33 shells and none of the albumens and yolks were positive for SE. All eggs that had SE-positive contents also had SE-positive shells.