Mice as carriers of Salmonella enteritidis on persistently infected poultry units

Evidence of the possible role of wild mice in the epidemiology of Salmonella enteritidis infection on broiler breeder and layer breeder units was obtained by a bacteriological examination of local mice. Persistent S enteritidis infection in birds on these units had been a problem and a high proportion of the mice were found to carry salmonella. S enteritidis was isolated from the liver and the intestine of most of the mice, indicating a systemic infection. Three-week-old chicks were infected by contact with droppings from mice which had been infected experimentally with S enteritidis two and five months previously. Wild mice infected artificially or naturally excreted S enteritidis intermittently, with up to 10(4) organisms in some individual droppings. A naturally infected mouse which died after intermittently excreting small numbers of S enteritidis in its droppings for 19 weeks had 10(4) organisms/g of liver and 10(3)/g of macerated intestine and contents. S enteritidis was also found in fetal tissue in a naturally infected mouse suggesting the possibility that the organism might be transmitted vertically.