Salmonella, the hidden danger for a planet with a future population of 9 billion. Meeting the zero standard in pig meat with strategies for controlling Salmonella . Catharina Berge, DVM, MPVM, PhD Berge Veterinary Consulting
Salmonella – Global health challenge
Salmonella infection from food is one of the major causes of human illness and responsible for substantial economic losses worldwide.
Every year: Millions of people infected with Salmonella by food and thousands die from the disease.
US- annual costs of human Salmonella infections estimated at $ 2.3 billion.
How much human salmonellosis from pork?
10-20% of human salmonellosis in EU from pigs and pig meat
6-9% of human foodborne salmonellosis in USA from pigs and pig meat
In Denmark, pork and pork products were reported to be responsible for 10-15% of the total Salmonella infections.
Differences between countries due to;
the Salmonella occurrence in pigs and pig meat,
consumption patterns & preferences
relative importance of other Salmonella sources.
Salmonella , not tolerated by consumers
Consumers are demanding food safety assurances, not only during slaughter, processing, and preparation, but also at the farm level.
Who has the responsibility?
a farm-to-fork approach.
the responsibility for the production of safe food lies with the primary animal producer up through the food chain to the consumer
Strategies and lessons learnt from Europe
Experience from Denmark
European Food Safety Risk Assessment
Tools to fight Salmonella
Benefits in Salmonella control
European Union study in slaughter pigs
10.3 % Salmonella -positive slaughter pigs. Varied from 0% to 29% between EU countries.
From 9 countries level the prevalence of slaughter pigs with antibodies against Salmonella ranged from 3.5% to 33.3%.
The top serotypes: Typhimurium, Derby, Rissen, S. 4,,12:i:- and Enteritidis.
Farm to consumption QMRA Transmission Cross-contamination Amplification Inactivation
QMRA-Hazard and risk characterization
Reduced Salmonella in pigs arriving at slaughter
by ensuring breeder pigs are Salmonella -free;
70-80% reduction in high prevalence areas
10-20% in low prevalence areas can be foreseen;
by feeding only Salmonella -free feedstuffs;
10-20% reduction in high prevalence areas
60-70% in low prevalence areas
by preventing infection from external sources of Salmonella (i.e. rodents and birds)
10-20% reduction in slaughter pig lymph node prevalence can be foreseen.
Ensuring that breeder pigs are Salmonella -free is the first step in high prevalence countries.
Control measures proposed:
(1) control in nucleus and multiplier herds
(2) incoming pigs ( Salmonella status)
(3) control of feed
(4) biosecurity programs incl. Salmonella .
Salmonella -infected breeder pig herds,
Salmonella -contaminated feed.
Slaughter house procedures
Slaughter house interventions are more likely to produce greater and more reliable reductions in human illness, at least in a shorter time frame, than can be achieved at the farm in high prevalence countries.
Countries can achieve more effective reductions in human cases by targeting both farm and slaughter house.
Effect on human Salmonellosis cases
a reduction of two logs (99%) of Salmonella numbers on contaminated carcasses would result in a 60-80% reduction of the number of human salmonellosis cases attributable to pig meat consumption.
Salmonella dynamics during slaughter of pigs
Salmonella increases during transport and lairage, where it reaches its maximum at kill.
Salmonella prevalence is reduced due to singeing,
Increases because of polishing, evisceration, and veterinary inspection.
pig carcasses are showered with 80 C (176 F) hot water for 14-16 seconds directly after slaughter.
2-log (100-fold) reduction of E. coli and Salmonella .
New method: a combination of steam and ultrasound.
Economic analyses have shown that steam ultrasound is the most cost-effective intervention followed by HWD.
Jensen, T. Christensen, H. Decontamination of pig carcasses with hot water. Proceedings 4th international symposium …(Safepork). 2001. Leipzig, Germany. Lawson L.G., et al . Int J Food Microbiol 2009:134: 126-132.
Hot water decontamination Photo from Danish Meat Research Institute
Denmark Cost Benefit Analysis
Identified the economical efficiency of a range of possible strategies.
None of the pre-harvest initiatives investigated resulted in a substantial reduction of the prevalence.
Only hot water decontamination turned out to be economically efficient.
Antigen presentation to immune system – immune modulation
Improved protection – optimising mucin layer
Mode of action of nutritional supplements
A number of carbohydrates (based on glucose, mannose, galactose, fucose) have been shown to have anti-infective properties
Mannose and its polymers are the most commonly used products as feed additives and have been shown to reduce Salmonella colonization in chickens.
Salmonella contain mannose-specific lectins (Type 1 fimbriae) on the bacterial surface that binds to glycoproteins (rich in mannose) on the intestinal surface.
Mannose sugars can thereby compete with the intestinal glycoproteins for attachment sites and prevent colonization.
Salmonella binding has been demonstrated with mannan- oligosaccharide (Bio-Mos) at significantly lower concentrations than that required for purified mannose. (Spring 2000)
Improve gut health
Optimal performance depends on good intestinal health
Salmonella exclusion also depends on excellent gut health
Use Bio-Mos as part of a control plan to optimise gut health and reduce Salmonella
Bio-Mos & Actigen-Nutritional Tools to include in Salmonella Control Plans
Where do we start?
Education and information
Slaughter house hygienic measures
Internal and External
Improve gut health and immunity
More research needed
Salmonella control-does it pay off?
Consumers, retail, restaurants and catering will use food safety criteria as quality criteria to promote their products.
Once food quantity has been secured, food quality will be driving the market
Salmonella control on farm and at slaughter
All biosecurity measures and hygienic measures to decrease Salmonella contamination will promote productivity and health
Measures to optimize pig gut health has direct return on investment
In processing, Salmonella control measures will improve food safety
Formic, acetic, propionic & butyric acids
Inclusion rate based on feed buffering capacity (0.5-3%)
Coated butyric acid decreased Salmonella levels in pig caecal content, whereas uncoated acids did not. (Boyen 2008)
Good for animal health and performance, variable results for Salmonella reduction
Less Salmonella in herds using home mixed wet feed than in those buying pelleted feed (Denmark, Greece)
Evidence that coarse ground meal can decrease Salmonella (Mikkelsen 2004)
Feed is kept longer in stomach-- increases acidity of feed
Competitive Exclusion (CE)
a kind of probiotic culture that is only given at a single time to the animals.
It was initially used in poultry production, where newly hatched chicks can be protected from subsequent Salmonella infections by accelerating the establishment of a complex, protective microflora. (Nurmi, 1992)
CE cultures to neonatal piglets have been shown to reduce Salmonella choleraesuis fecal shedding in pigs and contact pigs during preweaning and weaning period. ( Genovese, 2007)
Medium chain fatty acids (MCFA)
caproic, caprylic, capric acids.
MCFA decrease Salmonella in vivo in birds (Van Immerseel, 2004)
It was proposed that they reduce the invasive capacity of Salmonella by decreasing the expression of genes specifically involved in invasion.
In vitro laboratory study simulating the porcine cecum indicated that Salmonella could be inhibited by MCFA (Messens 2009)
Oligosaccharides (soluble fiber), but can also be proteins, peptides and some types of lipids.
Defined as non-digestible feed ingredients that beneficially affects the host by selectively stimulating the growth and/or activity of bacteria in the colon and thus improves host health . (Gibson 2005)
These prebiotics feed probiotics or commensal enteric bacteria and could give them a competitive advantage over potential pathogens such as Salmonella .
Fructo-oligosaccharides and inulin rat studies indicates that there may be increased colonization with Salmonella using these products . (Ten Bruggencate, 2004)
A range of essential oils have been shown to have bacteriostatic or bacteriocidal properties against Salmonella in vitro.
There is lacking studies about the applicability in pig feed as a Salmonella intervention.
Currently 17 products approved in EU for pigs ( Regulation (EC) No 1831/2003 )
Lactic acid producing probiotics have been shown to decrease Salmonella infection in pigs. (Casey 2007)
A systematic review – feed and feeding management to reduce Salmonella in slaughter swine
O’Connor, AM. Prev Vet Med. 2008 Nov 17;87(3-4):213-28.
Screened 248 studies, evaluated 15
a low level of comfort among qualified scientists that the claimed association between non-pelleted feed and reduced Salmonella prevalence is scientifically valid.
There is no strong evidence regarding associations between Salmonella and feed withdrawal prior to slaughter, feed acidification, heat treatment of feed, pelletized feed versus mash, and wet versus dry feeds.
Summary of responses to Bio-Mos ® addition to sow diets