|Nisbet, David - Dave|
|Buckley, Sandra - Sandy|
Submitted to: Research in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/1998
Publication Date: N/A
Citation: Interpretive Summary: The United States swine industry losses millions of dollars each year because of infection of pigs by pathogenic Salmonella bacteria. Pigs infected by Salmonella are typically poor growers and many die. Additionally, meat from infected pigs is unsafe for human consumption. It is not known for sure when most pigs become infected but it is known that disease occurs most often following weaning. It is also known that stressful events tend to promote fecal shedding of Salmonella from infected pigs. We conducted an experiment to study infection of weaned pigs by Salmonella choleraesuis, the type of Salmonella that causes the most disease in pigs in the United States. We found that the best way to experimentally infect pigs with Salmonella choleraesuis was to give pigs an oral dose of 100,000,000 cells of our laboratory grown Salmonella. The pigs we infected did shed the pathogen in their feces and this caused infection of pigs not previously exposed to Salmonella. Our results suggest that strategies designed to reduce shedding of Salmonella choleraesuis by infected pigs can be used to prevent the spread of this pathogen to other pigs.
Technical Abstract: A model for experimental and natural infection of early weaned pigs with Salmonella choleraesuis has been developed. An oral dose of 10**8 colony forming units (CFU) of S. choleraesuis caused 100% infection of ten pigs inoculated, as indicated by recovery of the challenge organism from ileocolic lymph nodes collected at necropsy seven days post challenge. Seven of the pigs were observed shedding S. choleraesuis at least once post S. choleraesuis challenge. The cumulative incidence of shedding was 30% and this was sufficient to infect four of ten pigs naturally exposed. Oral challenges with less than 10**8 CFU S. choleraesuis were less effective in infecting early weaned pigs and did not result in natural transmission.