In recent years Campylobacter has overtaken and now far exceeds Salmonella as the leading cause of human bacterial gastroenteritis. Pigs can carry and infect humans with Campylobacter, however poultry is estimated to be responsible for up to 80% of human campylobacteriosis. In this article we will focus on covering the basics of Campylobacter jejuni in poultry: What is it? Where does infection happen? And what means for curing or prevention are available?
Campylobacter is a zoonotic pathogen which means it can be transmitted via infected host animals and cause disease in humans. Humans are typically infected through consumption of chicken meat products contaminated with Campylobacter. The Campylobacter bacteria are usually isolated to the intestines but can contaminate the meat during slaughter and carcass processing.
Campylobacter in poultry
It is important to remember that to the chicken Campylobacter is not pathogenic so will not cause disease. Humans on the other hand are very susceptible and once infected show symptoms of severe bowel and stomach cramping, fever and hematochezia (blood in the feces).
The chicken is usually infected between 2-4 weeks of age, before that age they are protected by maternally derived antibodies which protect against colonization. Campylobacter is highly infectious and will colonize over 95% of the flock within days.
The source of infection can be drinking water, the environment or other chickens. To become successfully established Campylobacter must colonize the chicken gut and in particular the caeca.
Important factors which help campylobacter to achieve this are:
- Chemotaxis (the bacterium senses which way to travel)
- Bile resistance (thereby bypassing an important defense mechanism)
- Flagella and motility (these are used for movement and adherence)*1
- Immune system evasion and multidrug resistance
- Adhesion to epithelial cells (production of adhesins)
- Invasion of the gut-wall
Despite years of research there still is no effective way to completely clear this zoonotic pathogen from chickens. The most promising at this point in time would appear to be vaccines. Recently researchers have also begun to attempt to breed Campylobacter-resistant chickens*2. Promising as these solutions may be, they are still years away from becoming commercially available. Therefore other routes of intervention have been studied namely the roll of essential oils and organic acids in drinking water and in feed.
Acids and essential oils vs. Campylobacter
In a recent study it was shown that a particular essential oil not only had a pronounced effect on Salmonella enteriditis but even more so on Campylobacter jejuni. This trial was conducted in drinking water of chickens as this can be a major route of infection and colonization.
In another trial acidification of the drinking water was studied to see if this could prevent transmission from infected bird to uninfected bird, another important route of infection. It was found that acidification of drinking water indeed has an effect on the transmission rate.
The microflora route
A third option that has been looked at is the modulation of the micro-flora in the intestinal gut. It is thought that by maintaining excellent gut health, Campylobacter colonization and invasion could be reduced by competitive exclusion.
Products that could achieve this are:
- Organic acids and in particular butyric acid
By modulation of the gut-flora not only will there be competitive exclusion but in the case of butyric acid also an influence on the gut-wall which could make it more resistant to adherence and invasion. However, these theoretical benefits still need to be researched further.
Despite the huge strides that have been made with Salmonella control in poultry this has not been the case with Campylobacter. Currently the vast majority of food poisonings in the developed world is due to Campylobacter. Although in some countries in the EU this has received top priority, a solution to this problem remains elusive. Further research on both the pharmaceutical as well as the feed additive side remains needed.