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Salmonella widespread in pig breeding farms

35/2009, 17.12.2009

The results of a nationwide study coordinated by BfR indicate that Salmonella can frequently be detected in pig breeding stocks. In most cases, however, only a small number of pigs are infected. The study is part of an investigation of pig breeding stocks conducted last year in the European Union (EU). The results of the EU-wide study were published today by the European Food Safety Authority (EFSA). According to the BfR report, that was also published today, Salmonella were detected in mixed samples from the faeces of several animals in Germany in 45 out of the 201 stocks examined with more than 50 breeding pigs (22.4%). "Infected piglets from the breeding stocks can carry over Salmonella to the fattening stocks", says BfR President Professor Dr. Dr. Andreas Hensel. From there the Salmonella can reach the food chain through infected slaughter pigs. Hence, special attention should be paid to kitchen hygiene when preparing meat.  In principle, meat should only be eaten once it has been thoroughly cooked through. This is how to inactivate not only the Salmonella but also other possible pathogens.

Salmonella are frequent pathogens of infections of the gastrointestinal tract in humans. Many of these infections are caused by eating meat contaminated with Salmonella. Besides eggs and poultry, pork is one of the most frequent sources of infection.

In 2008 17 different serovars were identified in the Salmonella detected in the pig breeding stocks according to the National Reference Laboratory for Salmonella attached to BfR. The most frequently detected serovars were Salmonella Derby (8.4 percent) and Salmonella typhimurium (3.6 percent). Salmonella typhimurium is the second most frequent pathogen of salmonellosis in humans.  It was detected the most frequently in a study on Salmonella in slaughter pigs that EFSA and BfR both reported on in 2007.

In more than half of the breeding stocks, in which Salmonella were detected, only one or two of the 10 faeces samples examined tested positive for Salmonella. This indicates that only a small proportion of the animals in the stocks is carrier of and excrete Salmonella. Larger stocks were more frequently Salmonella-positive than smaller ones.

Salmonella infection in pigs is not normally coupled with a disease. This means that the germ can often go undetected in the herd and spread from farm to farm through infected piglets. The control of Salmonella in Germany has been regulated since 2007 by the Pig Salmonella Ordinance.

The European study shows that Salmonella were detected in pig breeding stocks in all Member States that engage in intensive pig production. In total, 30.9 percent of the pig breeding stocks in the EU were infected with Salmonella. The range of infection rates extends from zero to 58 percent of the stocks examined. Here, too, Salmonella Derby and Salmonella typhimurium were the most frequently detected serovars.

The results of the studies on slaughter and breeding pigs are to serve as the basis for the setting of targets for Salmonella control in the EU.

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