WHITE PAPER BACKGROUND - SALMONELLA, PIGS AND HUMAN SALMONELLOSIS Salmonella are Enterobacteriacea bacteria that are carried by some animals, including pigs, and which can be transmitted through water, soil, animal feces and gut contents, raw meats, and eggs. Pigs have been found to be the predominant animal reservoir for Salmonella (Cantoni & Bersani, 2010). Salmonella in pigs is found mainly in the intestines, lymph nodes and tonsils. The EFSA survey, published in 2008 (EFSA, 2008a) found that an average of 10.3% of pigs at slaughter were positive for Salmonella from these sources. They also investigated external carcass contamination and found an average prevalence of 8.3%. Of the Salmonellas found Salmonella Typhimurium and Sal monella Derby represented 40% and 14% of these respectively (EFSA 2008a). These Salmonellas are the same as those often found in cases of human infection. Consequently, there is now increasing focus on reducing the prevalence of Salmonella contamina tion on pig meat as a means of reducing human infection. Salmonellosis is a foodborne illness caused by the Salmonella bacteria. Salmonella infections in humans typically affect the intestines, causing vomiting, fever, and other symptoms that usually resolve without medical treatment. The main risk factors leading to the contamination of pork with Salmonella are 1) infected herds, 2) poor hygiene standards at all stages of pork processing, and 3) poor cross-contamination control. SALMONELLA CROSS-CONTAMINATION WITHIN PIG PROCESSING There are a number of stages at which Salmonella can spread within pork processing: • At the farm – here the focus should be on the rearing of Salmonella-free pigs. Poor hygiene has been identified as one of the most important risk factors for high salmonella prevalence in positive herds. Investigation of the Danish pig industry showed that even a relatively low prevalence of Salmonella in primary production can result in a high numbers of contaminated carcasses at the slaughterhouse-level. • During transport – Transport vehicles are rarely cleaned adequately between loads and conse quently can become highly contaminated with organic matter and bioflims as a result of anal evacuations, encouraged by fasting and the transportation stress, by infected pigs. • During lairage – Similarly, build up of contamination in the lairage and cross-contamination between infected and Salmonella-free animals can lead to the spread of Salmonella. The majority of the studies carried out conclude that lairage pens represent a very important source of infection for the pigs housed in them and that contamination of the environment by the infected pigs contributes to the spread of the infection to the healthy pigs. Initial infection of the tonsils of a Salmonella-free animal can spread, via the lymph, to reach the colon and rectum in <3 hours (Fedorka-Cray et al. 1994). Also, the lairage cleaning and disinfection protocols are very ineffective. The Salmonella strains found in the lairage pens have been frequently related to the strains present in the carcasses. • In the slaughterhouse – The slaughterhouse en vironm ent is probably the major source for Sal monella infections (Fedorka-Cray et al. 1994; Hurd et al. 2001a&b; Swanenburg et al. 2001). Final carcass contamination rates in the abattoir have been found to be seven times higher than those on the farm and 50% of the carcasses contaminated by Salmonella were due to cross-contamination. This contamination of the environment is attributed to anal leakage and gut rupture after evisceration. Vikan A/S - Department of Research & Development 02 Copyright © 2013 Vikan A/S · All Rights Reserved
Download PDF file