Rapid infection in market-weight swine following exposure to a Salmonella typhimurium-contaminated environment.
OBJECTIVE
To evaluate the possibility of swine becoming infected with Salmonella Typhimurium when housed for 2 to 6 hours in an environment contaminated with Salmonella, similar to a lairage situation prior to slaughter.


METHODS
40 crossbred market pigs with an approximate body weight of 92 kg.


METHODS
Five trials were conducted (8 pigs/trial) in simulated lairage conditions. Superficial inguinal, ileocecal, and mandibular lymph nodes, cecal contents, distal portion of the ileum, and fecal samples were obtained from each pig after 2 (n = 10), 3 (10), and 6 (5) hours of exposure to an environment contaminated with feces defecated by 10 pigs intranasally inoculated with nalidixic acid-resistant Salmonella Typhimurium (chi4232). In addition, 5 control pigs that were not exposed were also evaluated in the same manner.


RESULTS
Feces deposited on the floor by intranasally inoculated swine were mixed with water to form slurry with a resulting load of approximately 10(3) colony-forming units of Salmonella Typhimurium/g of material. Eight of 10, 6 of 10, and 6 of 6 pigs exposed to the slurry for 2, 3, or 6 hours, respectively, had positive results for at least 1 sample when tested for the specific strain of Salmonella Typhimurium.


CONCLUSIONS
Pigs can become infected during routine resting or holding periods during marketing when exposed to relatively low amounts of Salmonella organisms in the preslaughter environment. Intervention at this step of the production process may have a major impact on the safety of pork products.
Hurd
H S
HS
National Animal Disease Center, USDA, Agricultural Research Service, Ames, IA 50010, USA.
Gailey
J K
JK
McKean
J D
JD
Rostagno
M H
MH
D000003:Abattoirs; D000818:Animals; D004064:Digestive System / Q000382:microbiology; D005243:Feces / Q000382:microbiology; D005260:Female; D008198:Lymph Nodes / Q000382:microbiology; D008297:Male; D011897:Random Allocation; D012481:Salmonella Infections, Animal / Q000382:microbiology / Q000635:transmission*; D012486:Salmonella typhimurium / Q000254:growth & development*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology* / Q000635:transmission