Rapid infection in market-weight swine following exposure to a Salmonella Typhimurium-contaminated environment

H. Scott Hurd Pre-Harvest Food Safety and Enteric Diseases Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, PO Box 70, Ames, IA 50010.

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 DVM, PhD
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Jared K. Gailey Pre-Harvest Food Safety and Enteric Diseases Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, PO Box 70, Ames, IA 50010.

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James D. McKean Department of Veterinary Diagnostics and Production Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011.

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Marcos H. Rostagno Pre-Harvest Food Safety and Enteric Diseases Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, PO Box 70, Ames, IA 50010.

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Abstract

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.

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

Procedure—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 (χ4232). 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 103 colonyforming 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 and Clinical Relevance—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. (Am J Vet Res 2001;62:1194–1197)

Abstract

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.

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

Procedure—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 (χ4232). 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 103 colonyforming 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 and Clinical Relevance—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. (Am J Vet Res 2001;62:1194–1197)

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