Poultry Infections by Campylobacter jejuni and Their Control

Dr. B. Allan
Research Scientist
Food Safety Group
Veterinary Infectious Disease Organization

Poultry Service Industry Workshop
October 2002

Much of the worldís poultry production is contaminated with campylobacters and this has been implicated as a major source of human infection. Removal of these organisms from the poultry food chain or at least a reduction in their frequency has become a significant objective of campylobacter research. There are three practical levels at which infection control could be targeted and implemented: at the poultry farm, during poultry meat processing, and during handling and cooking by the consumer. In this talk I will focus my attention on intervention strategies on the farm.

The prevalence of C. jejuni positive flocks worldwide appears to be variable. Reports range from 18 to 95% positive flocks. This variability may be due in part to the type of sampling and method of bacterial isolation used. Most studies have been done on chickens but significant levels of colonization have also been reported in ducks, pigeons, quail, ostriches and turkeys. Any avian species may be colonized. It appears that campylobacter has evolved to optimally grow in the avian gut environment. This may make elimination of colonization difficult.

Colonization of poultry does not result in disease but is commensal in nature. Colonization is found largely in the ceca and is confined primarily to the intestinal mucus layers in the cryps of the intestinal epithelium. C. jejuni, however, has been recovered from extra intestinal sites, including the liver and spleen, in asymptomatic birds. This may be the reason for a strong immune response in birds despite the apparent lack of disease.

It is clear from longitudinal studies in commercial broiler houses that there is an age-related increase in the prevalence of colonization of birds. In most flocks studied, no colonization of birds is observed before 10 days of age. Around two weeks of age colonization of some birds can be detected. The reason for this lag phase is not known but is unlikely to be due to lack of exposure to this ubiquitous bacteria. It has been suggested that this lag in colonization is due to maternal antibodies, antibiotic feed additives and competition by the normal gut flora. More research is needed to establish the nature and mechanism of this effect.

The duration of colonization and shedding has not been fully investigated. It is accepted that chickens, once colonized, remain chronically infected for many weeks. For broiler chickens this condition continues until the time of slaughter.

Mixed infections with C. jejuni may occur. More than one strain may be isolated from an individual bird or from a single flock. Strains of campylobacter vary in their ability to colonize poultry. Strains with a high colonization potential are able to replace others. It is not known if strains with a high colonizing potential in poultry are also more virulent for humans. Understanding what allows an individual strain to be a good colonizer of poultry may provide information that will be useful in controlling the problem.

In principle, intervention to control C. jejuni contamination of poultry meat could occur at any stage from farm to fork. Flocks are not screened for colonization by C. jejuni before they are shipped to abattoir. The first flock that is colonized contaminates the environment of the abattoir. All subsequent flocks processed before the environment is decontaminated may become contaminated .To prevent this type of cross contamination intervention strategies at the farm will be most effective. It is possible, using molecular techniques to rapidly determine if campylobacter is present in the flock. In the future it may be possible to screen all flocks before they leave the farm.

Some debate still exists about the source of infection in poultry flocks. Vertical transmission from eggs has been reported but its role is not clear. There is no direct relationship between flocks that are positive for C. jejuni and hatchery source suggesting that vertical transmission is unlikely. It is more likely that the primary transmission is horizontal in nature. C. jejuni is known to contaminate the environment around and within the broiler house. Therefore biosecurity plays a major role in the decrease in colonization of poultry and provides the primary barrier.

Significant ways to reduce the risk of infection at the farm include:

ï Good condition of housing

ï Vermin control

ï Removal of dead birds

ï Effective cleaning and disinfection of all equipment entering the site

ï Sanitation of drinking water during the life of the flock

ï Dust removal

ï Frequent replenishment of foot dips

ï All in - all out stocking

ï Allowing a down period between flocks

ï Wise choice of disinfectant

Catching gangs and their equipment may also be responsible for the introduction of campylobacter to flocks. Ineffective cleaning of transport crates has been shown to lead to an increase in campylobacter contamination.

Competitive exclusion has been effectively used to control salomonellosis in chickens and this approach is being studied for the exclusion of campylobacter. Bacterial isolates derived under various conditions from chicken feces or intestinal contents have been tried. Their efficacy against campylobacter appears variable at best. This may be due to the variable content of the agents tested. A defined flora, which would provide predictable efficacy against C. jejuni, would be optimal. However, to date such a product is not available.

Vaccination to prevent colonization with C. jejuni is also an area of active research. Colonization of chickens with C. jejuni induces both systemic and mucosal immune responses. The potential protective nature of these anticamplyobacter antibodies has not been well studied. Antibody responses appear to partially protect birds from colonization when rechallenged with the same strain.

Effective vaccine strategies for poultry have not been developed to date. Such vaccination strategies must either protect birds from exposure from day of age until slaughter or must eliminate colonization by the time of slaughter. It has been suggested that immunization of the parent flocks to produce passively protected chicks may be effective in delaying or reducing colonization by camplyobacter. The choice of vaccine candidates and the delivery system will dictate the outcome of any immunization. More work is required to optimize the vaccination strategies for the prevention of colonization by campylobacter.

The methods that were successful for controlling salmonella infections in poultry are generally ineffective against campylobacter. To identify a practical and sustainable strategy (or group of approaches) to prevent the colonization of poultry by C, jejuni more information about the epidemiologist, physiology and ecology of this organism in the avian host is required.

References

General Information:

Campylobacter 2nd edition. 2000. Edited by I. Nachamkin & M. J. Blaser. ASM Press Washington, D. C.

Other References:

Shane, S. M. 1992. The significance of Campylobacter jejuni in poultry: A review. Avian Pathology 21: 189-213.

Shani, O. et al. 2001. Prevalence, antigenic specificity, and bactericidal activity of poultry anti-Campylobacter maternal antibodies. Applied and Environmental Microbiology 67:3951-3957.

Cawthraw, S. et al. 1994. Isotype, specificity, and kinetics of systemic and mucosal antibodies to campylobacter jejuni antigens, including flagellin, during experimental oral infection of chickens. Avian Diseases 38:341-394.

Khoury,C. A. and Meinermann. 1995. A genetic hybrid of the Campylobacter jejuni flaA gene with LT-B pf Escherichia coli and an assessment of the efficacy of the hybrid protein as an oral chicken vaccine. Avian Diseases 39: 812-820.

Stern, N. J. et al. 1990. Influence of host linage on cecal colonization by Campylobacter jejuni in chickens. Avian Diseases 34:602-606.

Lister, S. 2002. Campylobacter-the lurking menace. International Poultry Production 10: 15-19.

WEB Site: http://www.antecint.com/main/camppou.htm. Campylobacter in poultry-a HACCP approach to control.