With Campylobacter causing serious human health issues, supermarkets are pressuring producers to lower meat contamination. Management measures have obtained results but there remains much to do with regards to research in which additives and physical measures lead to the best reduction.
Campylobacter has become the most frequently reported cause for food-related gastroenteritis and costs the 28 member countries of the European Union €2.4 billion annually. In the UK, Campylobacter is estimated to cost the poultry industry up to £20 (€26) per thousand broilers.
It continues to receive a great deal of attention in Western Europe, since the release of the UK Food Standards Agency’s (FSA) survey findings of Campylobacter contamination in supermarket chickens, leading supermarkets to put greater pressure on their suppliers to reduce contamination levels.
Campylobacter species are not necessarily commensal bacteria. In poultry they have been shown to have the potential to cause disease, diarrhoea and reductions in feed efficiency. The overall level of Campylobacter contamination throughout the EU varies by country, there is a marked variation of contamination which may be partly explained by climate. Campylobacter incidences traditionally increase in the warmer summer months. 15 of the then 27 EU member states registered moderate to high levels of Campylobacter in broilers (Figure 1).
Any improvement in biosecurity will have benefits to disease control
Heightened biosecurity has been shown under experimental conditions to reduce the levels of positive flocks by up to 70%. However, in a commercial operation lapses do occur thereby reducing the efficacy of just biosecurity as the major way of combatting the disease on the farm. Many companies and farms have already increased the levels of biosecurity being employed and the results of this drive have still to be seen in overall contamination. However any improvement in biosecurity will have other benefits with regard to disease control.
Table 1 recaps a previous review of the status of several methods of reducing Campylobacter contamination rates (See Campylobacter, a European problem published in World Poultry issue 7 in October 2015).
Several ‘in feed’ additives have been tested for their ability to reduce the levels of Campylobacter contamination into the slaughter house as part of an overall Campylobacter reduction programme. However despite being effective in vitro there are differences in efficacy between the additives when used in vivo.
Bacteriocins can reduce the levels of caecal campylobacter in infected birds
Bacteriocins are proteinaceous toxins which are part of the natural defence mechanisms of bacteria and can be produced by both Gram-positive and Gram-negative bacteria. Whilst most bacteriocins exhibit anti-bacterial properties only to closely-related bacteria, some have broader spectrum effects.
The action of bacteriocins against specific bacteria involves binding onto the cell wall of the target bacteria and creating a pore in the outer membrane. Leakage of inorganic ions through the pore leads to the death of the target bacteria.
Today, the food industry comprises the main area of use of bacteriocins, though a limited number of bacteriocins have been shown to have anti-campylobacter properties. These are mainly produced by Bacillus circulans and Paenibaccilus polymyxa, Lactobacillus salivarius Enterococcus faecium.
Scientific trials have been conducted to show that the use of bacteriocins can be effective in reducing the levels of caecal Campylobacter in infected birds. However, more work is required to ensure that this method can counteract a variety of Campylobacter species and genotypes. Further large-scale testing will be needed to evaluate the efficacy of bacteriocins.
Bacteriophages can be given to infected flocks before slaughter to help reduce campylobacter
Bacteriophages are naturally occurring viruses which can infect, multiply and kill susceptible bacteria. They are ubiquitous in the environment and can be found wherever suitable bacterial hosts proliferate. Of the two types of bacteriophages, lytic and lysogenic, only the former are suitable for treatments. Lytic bacteriophages invade the cell, replicate and finally burst the cell to release more bacteriophages that then repeat the process.
Scientific trials using bacteriophages have shown great promise with the reduction of caecal Campylobacter by between 0.5 to 5 Log₁₀. Their use tends to be therapeutic, given to infected flocks 2 to 3 days before slaughter, rather than prophylactic since their efficacy relies on the presence of a sufficient number of host bacteria.
Some trial work has also been carried out on the use of bacteriophages in the final rinse of carcasses in the slaughter house where some satisfactory results have been obtained. However, this type of process could be difficult to register within the EU due to the ongoing activity on the carcass surface itself.
Tests in supermarkets reveal a high incidence of campylobacter, supermarkets demand that their suppliers tackle the problem.
In vitro tests show the benefits of organic acids against campylobacter
Organic acids have been included in poultry diets for many years to improve feed hygiene by way of combatting bacterial contamination in feed, particularly Salmonella. Similarly, addition of organic acids to drinking water can have hygiene-enhancing effects.
Intervention with organic acids has not been included in the model for quantitative risk assessment (dubbed Campylobacter Moments, or CAMO) because “the results through feed or water have given inconsistent results in terms of numbers and prevalence on Campylobacter” according to the EFSA. Many in vitro tests have shown significant benefits of organic acids against Campylobacter, though in vivo experiments with chickens have given mixed results.
Adding formic acid alone into feed had no effect on the colonisation of Campylobacter in one recent study, for example. A combination of organic acids has had more success. A mixture of 1.5% formic acid and 0.1% potassium sorbate significantly reduced Campylobacter colonisation. Increasing the level to 2% formic acid and 0.1% potassium sorbate prevented colonisation altogether.
Combinations of organic acids in the drinking water during the later stages of growth, thinning and final slaughter have shown some positive effects in the reduction of Campylobacter colonisation, particularly when given during the feed withdrawal stage. In order to achieve optimum results, the pH of the water has to be lowered to between 4.0 and 4.5.
Phytogenic feed additives help boost liver function and gut health
Phytogenic feed additives (PFAs), or botanicals, cover a wide number of plants and herbs and can be derived from either ground plants themselves, essential oils from the herbs and spices or even nature-identical synthetic active ingredients from individual essential oils. With such a range of potential substances and ingredients, many will not have direct antimicrobial actions. Instead, they work in the intestine in alternative ways: by boosting palatability and appetence, liver function, gut health and function, acting as an anti-inflammatory and even improving nutrient digestibility.
Several in vitro trials have been carried out to check the anti-bacterial properties of some plant-derived products and essential oils against Campylobacter spp with some success. However, in vivo testing in broilers showed no reduction in shedding of Campylobacter to the desired level.
With the range of potential ingredients and combinations in this category of feed additive, much more research will need to be carried out before any phytogenic substance can be shown to give the required reduction in caecal contaminations consistently.
Probiotics can help reduce the levels of colonisation of Campylobacter jejuni
Probiotics, or direct-fed microbials, are live microbial supplements which beneficially affect the host when given in adequate amounts in feed, or water, by improving its intestinal microbial balance. Probiotics have been used to control various disease challenges for many years and were first used commercially in the early 70s to control an outbreak of Salmonella in Finland.
Probiotics act in the intestine in many different ways, from the basic competitive exclusion of pathogens through blocking attachment sites on the intestinal epithelium, lactic and acetic the acid production, bacteriocin production, to immune modulation through both innate and adaptive immunity.
Research has found that an avian-specific probiotic could reduce the level of colonisation and shedding of Campylobacter jejuni challenged broilers reared to 42 days of age. Additional trials have shown that other avian-specific probiotic combinations with a prebiotic can also significantly reduce the levels of colonisation of Campylobacter jejuni in the caeca when the chicks are either directly challenged or challenged through co-habitation with challenged chicks.
Combined measures needed to tackle threat of campylobacter
There is no ultimate response which will remove the threat of campylobacteriosis in people coming directly or indirectly from poultry. The lack of an available vaccine now and in the near future means that the industry will need to apply a series of measures in order to reduce Campylobacter contamination levels. To achieve this will require a mixed approach starting with improved biosecurity measures, changes to management practices, proven feed or water intervention with additives and, finally, intervention measures during slaughter in order to further reduce the contamination levels and risks of cross contamination.
Each of the interventions will help reduce the overall contamination and combined they will possibly give the required reduction of Campylobacter contamination of finished broiler meat. There remains much to do in regard to research in which additives can be successful but perhaps at the present time probiotics may become the additive of choice.
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