Effects of challenge dose on faecal shedding of Salmonella enteritidis in experimental infected chickens

Experimental infection of chickens with Salmonella enteritidis is often achieved by oral inoculation of live bacteria to caged chickens. Less information is available on influence of amount of Salmonella achicken is exposed to during infection on the proportion that is eventually eliminated in faeces. This study evaluated the effects of challenge dose of S. enteritidis on faecal shedding by experimentallyinfected chickens. Twenty four specific-pathogen-free hens were divided into three groups of eight. The first two groups were orally challenged with a dose of 1.3 x 104 and 1.3 x 108 colony forming units (cfu) of S. enteritidis per hen, the third group was uninfected. Faecal samples were collected weekly for 5 weeks and cultured. Levels of S. enteritidis recovered from hens infected with 108 cfu/ml S. enteritidiswere significantly higher (P < 0.05) than from 104 cfu/ml group. Rate of faecal shedding decreased from 100 to 75 and 37.5% at weeks 1, 2 and 4 respectively in 108 cfu infected hens. Intermittent sheddingpattern was observed in the 104 cfu group. Hence, Salmonella contamination of poultry environment continues in sub-clinical infection. Multiple faecal sampling of flocks may be necessary to know their Salmonella status and in vaccine assessment