Long-term shedding of Salmonella enteritidis in chickens which received a contact exposure within 24 hrs of hatching.

Abstract

Rifampicin-resistant mutant of Salmonella Enteritidis was used for the experiment of long-term excretion in chickens. Thirty-five specific pathogen free chicks within 24 hrs of hatching were placed in contact with 18 chicks inoculated orally with 4 x 10(2) CFU of S. Enteritidis HY-1 Rif within 12 hrs of hatching. After 7 weeks of the contact exposure, samples of cecal droppings were examined for the isolation of S. Enteritidis weekly or biweekly. Twenty-five out of 35 chicks (71%) survived. S. Enteritidis was isolated intermittently at least until 28 weeks after the contact exposure for male chickens and 21 weeks for female chickens although this strain could be isolated only for one or two months from cecal droppings or internal organs of young chickens and laying hens. In order to prevent S. Enteritidis infection in poultry, it was concluded that (1) the contact exposure within 24 hrs of hatching or transovarian infection should be avoided because infection of chicks within 24 hrs of hatching with S. Enteritidis causes the prolonged cecal shedding, and that (2) the isolation of S. Enteritidis from cecal droppings should be repeated because of its intermittent shedding.