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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #117695
Title: RAPID INFECTION IN MARKET SWINE FOLLOWING EXPOSURE TO A SALMONELLA TYPHIMURIUM-CONTAMINATED ENVIRONMENT

Author
item HURD, HOWARD
item GAILEY, JARED
item MCKEAN, J - IOWA STATE UNIVERSITY
item ROSTAGNO, MARCOS - 3625-30-15

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Transportation and long-term (> 12 h) holding prior to slaughter of swine have been associated with an increase in Salmonella prevalence at the packing plant. This increase in prevalence has been attributed to the effects of stress on immunity, increased mingling of animals, and reoccurrence of shedding. Little mention has been made regarding the environment as a source of Salmonella infection. The objective of this study was to evaluate the possibility of swine becoming infected with Salmonella typhimurium, in a 2-3 hour interval, from an environment contaminated with feces. This environment was designed to simulate the holding time prior to slaughter. Forty crossbred market weight swine (~92 kg) were exposed to marked strain of Salmonella typhimurium in simulated holding conditions. The contaminated feces were deposited on the floor by swine that had been intranasally inoculated 4 days previously. Exposed pigs were autopsied at 2, 3, and 6 hours after exposure to the contaminated floor. Within 2 hours, 80 % (8/10) of exposed animals were positive for the marked Salmonella typhimurium strain. At 3 hours after exposure 60% (6/10) of animals were positive on at least one sample cultured at autopsy. After 6 hours, 100% (5/5) of animals had at least one sample test positive. This study shows that market swine can become infected with Salmonella in the short waiting time before slaughter. Intervention at this step in the pork production process may have a significant impact on the safety of pork products. This information will be of interest to scientists, packing plant management, FSIS, and producers and practitioners.

Technical Abstract: To evaluate the possibility of swine becoming infected with Salmonella typhimurium from an environment contaminated with feces in a 2-3 hour interval designed to simulate the holding time prior to slaughter. Forty crossbred market weight swine (~ 92 kg). Five trials of eight market weight swine were conducted in simulated lairage conditions. From each animal, the superficial inguinal, ileocecal, and mandibular lymph nodes, as well as cecal contents, distal ileum portion, and feces were evaluated at 2 (n = 10), 3 (n = 10) and 6 (n = 5) hours after exposure to an environment contaminated with feces shed by swine intranasally inoculated (n = 10) with nalidixic acid-resistant Salmonella typhimurium (c4232). In addition, control animals with no exposure (n = 5) were also evaluated in the same manner. Feces deposited on the floor by intranasally inoculated swine were mixed with water to form slurry with a resulting load of ~ 10**3 Salmonella typhimurium CFU per gram. Eighty percent of animals with a 2-hour, 60% of animals with a 3- hour, and 100% of animals with a 6-hour exposure to this slurry had at least one sample test positive for the marked Salmonella typhimurium strain. Market swine can become infected during routine resting or holding periods when exposed to relatively low levels (10**3 CFU) of Salmonella in the preslaughter environment. Intervention at this step in the swine production process may have a significant impact on the safety of pork products.