The following is a summary of the key points in a very interesting article that appeared in the September 2014 edition of the French Poultry journal Filières Avicoles, "Campylobacter: stratégies de réductions envisagées" (Campylobacter: proposed reduction strategies), by G. Le Pottier, V. Elgosi, J. Mayot, Y. Carré.
- Campylobacteriosis is the most common zoonosis in Europe, with 214,268 cases reported in 2012.
- Estimated impact is €2.4 billion per year in Europe, where the main cause of the illness is chicken meat. Prevalence is worse for children under 5 years and routinely during the hottest months of the year.
- In 2012, prevalence was slightly less for first time in 5 years: down by 4.3% compared to 2011.
- It is a public health problem which European authorities must react to sooner or later; the most probable outcome is that a maximum contamination rate will be set (i.e. number of aerobic colonies on a skin sample) but that will take inevitably take time.
- Caused by Campylobacter, a gram negative bacteria. There are 23 species, the most significant of which are thermophiles (multiplying best between 32° and 47°C), as they are responsible for gastroenteritis in humans.
- Main strains are C. Jejuni (81% of cases reported in Europe) and C. Coli (6.2%). Minor strains are C.Lari, C. Upsaliensis, C.Helveticus, C.Fetus.
- Europe wide studies indicate an average prevalence in poultry batches of 71%. It spreads very rapidly by horizontal transmission (i.e. between non-relatives). It is asymptomatic, with no effect on production, which makes it undetectable to the breeder or abattoir. Contamination is passed down the production chain via faeces at the scalding or plucking stages, or by accidental rupture of intestines during evisceration.
- Campylobacter's natural reservoir is the digestive tracts of wild and domestic animals, including chickens, ducks, turkeys, pigs, ruminants, rodents, dogs, cats and insects (especially flies). Poultry meat is the main source of infection in humans, as there is a direct link between contamination in the flock and the carcasses. A growing number of cases are caused by other foods such as raw milk.
Strategies at the abbatoir
- Scalding tanks can be equipped with strong counter-flows and multiple tanks.
- Homogeneity in carcass size and machine settings are key factors. Significant size differences in carcasses or a badly adjusted machine can lead to intestines rupturing and spilling faecal matter on the slaughter chain and other carcasses.
- During the bleeding phase the bacteria are sealed into the pores of the skin, which contract due to the cold. Washing the carcasses prior to bleeding is not authorised in Europe and moreover, appears to be insufficient anyway. A study conducted in the United States where it is permitted revealed contamination rates of 39%, 83% and 81% of chicken carcasses selected at point of sale, from three of the largest producers in the country.
- Deep freezing can reduce contamination post slaughter, but this is not really a solution as the European market is mostly based on fresh meat.
The Campybro programme
- Is funded through the 7th European Union framework programme (http://campybro.eu) . It aims to control Campylobacter infections in broiler batches
- Two strategies to reduce Campylobacter contamination at production level: nutritional (feed additives and feed format) and developing a reverse vaccinology vaccine.
- Partners are European poultry production associations: Propollo in Spain, FIA and Cidef in France, Nepluvi in Holland and BTT in Hungary, a poultry producer (Explotaciones avicolas Redondo), a specialist vaccinology laboratory (CZVeterinaria), an analysis laboratory (Mikrolab) and two research centres (Anses in France and Imasde in Spain). The project runs from 2013-2016 and is coordinated by Imasde Agroalimentaria .
Preventive strategies for production
- Antibiotic therapies are not an option due to the high resistance of bacterial strains to different antibiotics (ciprofloxacin, erythromycin, gentamycin, tetracycline) and to the existence of multi-resistant strains.
- Biosecurity is extremely important. Creating physically separated zones (clean zone, dirty zone), using holdings and dedicated equipment, controlling insects. The role of insects - especially flies - in the contamination process is still not well understood, but there is promising data from studies in northern Europe. It is, however, difficult to control insects in breeding farms.
- Animals could be slaughtered earlier, as infection is greater towards the end of the batch. Females and males could be separated out to increase uniformity of carcasses at slaughter. Limits should be placed on multiple batch systems - rearing multiple batches at a time has a detrimental effect on biosecurity. If possible, a single batch should be reared at a time and the delay between removal and slaughter decreased to the minimum possible time. Catching teams should be trained in biosecurity measures. All of these management strategies have economic implications, so the risk is they won't be implemented.
- At the moment there is no commercially available vaccine. There are two European projects attempting to develop effective vaccines. Salmonella strains containing campylobacter genetic material can be used, or a bivalent vaccine (Katarcyna et al. 2009). The reverse vaccinology technique achieves equally good results for a lower cost (Ferreira & Porco, 2008)
- In the last five years, increased biosecurity measures have had little impact on campylobacter. The remaining solution is to fight infection through nutrition. The aim is to create a hostile environment for bacteria in the caecum, to block the massive colonisation by campylobacter. This can be achieved by the composition of the feed itself, or by using certain additives.
- In terms of feed composition and structure, different grades of fibre have a significant influence on intestinal microbiology. According to recent research, this is particularly true for soluble fibres, (Gonzalez Alvarado et al. 2007, 2008; Jimenez Moreno et al. 2000a,b,c).
- Fibre is important in chicken diets as it affects gizzard function (digestive process) and endogenous production of organic acids, which in turn impact the bacterial population.
- Moen et al. 2012 showed that 15% barley and oat husks slowed digestion and reduced campylobacter infections.
- The particle size also has an important effect on digestion: it has alread
y been shown in other species that coarse particles help reduce enterobacteria generally and salmonella in particular
- However, although granulated feed improves productivity (Serrano et al. 2012) this feed format also increases the wetness of the litter and thus numbers of E.Coli and Salmonella (Engbert et al 2002, Huang et al 2006)
- Some European countries are developing feed mixes containing whole wheat, based on the idea of using coarse particles.
Probiotics and plant extracts
- Probiotics improve intestinal flora out-competing other bacteria, but don't survive well in feed or the production process of feed and struggle to colonise the caecum effectively .
- Ghareeb et al. 2012 succeeded in preventing campylobacter contamination 8–15 days after infection, under experimental conditions, using a combination of Enterococcus, Pediococcus, Lactobacillus and Bifidobacterium.
- Plant extracts can also be used. The main benefit is that they reach the caecum in large quantities and their effectiveness is maintained. Friedman et al. 2002 studied the bactericidal activity against C. Jejuni of 96 essential oils and plant extracts in vitro. A large number of these had a bactericidal effect even in relatively weak concentrations, especially trans-cinnamaldehyde in cinnamon oil. However, Hermans et al 2011 found that trans-cinnamaldehyde failed to prevent or reduce contamination of the caecum by C. Jejuni. Robib et al 2013 found that campylobacter levels were slightly reduced when a garlic-based product was added to drinking water.
Efficacy of medium chain fatty acids
- Medium chain fatty acids (MCFA) are the additives demonstrated to be most effective against campylobacter but studies are contradictory: an in vivo effect of caprylic acid was found by Solis de los Santos (2008,2010), Van Gerwe et al (2010), Hermans et al. (2012), but others found no such effect and also demonstrated in vitro that chicken mucus inhibits the effects of those compounds (Metcalf et al 2011; Hermans et al. 2010).
- MCFAs are difficult to use in practice as they are hydrophobic and have an unpleasant odour. Monoglyceride fatty acids are a possible alternative. Hilmarsson et al. (2006) showed in vivo that when monocaprine is added to drinking water it can reduce the prevalence of campylobacter. Subsequently, Thormar et al. (2006) confirmed that stable solutions of monocaprine have a potential effect on campylobacter. MCFAs react differently in the digestive process when bound to a glycerol molecule: they don't need an acid environment in order to be effective and they are more likely to reach lower strata where bacteria are located. Monoglycerides are more easily added to drinking water, have more favourable organoleptic qualities and their effect is less dependent on the pH of the digestive tract.
- Another method is to combine them with short chain fatty acids, which can prevent gastro-intestinal infections, so that the monoglycerides can act directly on microbe populations.