EXPERIMENTAL AND NATURAL INFECTION OF EARLY WEANED PIGS WITH SALMONELLA-CHOLERAESUIS

A model for experimental and natural infection of early weaned pigs wi th Salmonella choleraesuis, the aetiologic agent of swine paratyphoid, has been developed. An oral dose of 10(8) colony forming units (cfu) of S choleraesuis caused 100 per cent infection of 10 pigs inoculated, as indicated by recovery of the challenge organism from ileocolic lym ph nodes collected at necropsy seven days post challenge. Seven of the pigs were observed shedding S choleraesuis at least once post S chole raesuis challenge. The cumulative incidence of shedding was 30 per cen t and was sufficient to infect four of 10 pigs exposed naturally. Oral challenges with less than 10(8) cfu S choleraesuis were less effectiv e in infecting early weaned pigs and did not result in natural transmi ssion.