Campylobacter – How does it get in the chicken?
Researchers at USDA’s Russell Research Center performed a series of studies in an attempt to understand the primary source of Campylobacter and thus lead to its control.
Campylobacter contamination continues to plague the poultry industry. As with other potential human pathogens the source can be confusing. This confusion makes control very difficult. Researchers at USDA’s Russell Research Center performed a series of studies in an attempt to understand the primary source of Campylobacter and thus lead to its control.
This elusive but prevalent organism has been detected on more than half of the broilers tested indicating a relatively high prevalence. Its presence in every aspect of the commercial broiler operations, from the breeder farm through the hatchery, to the broiler flock and finally to the processing plant, has been clearly demonstrated.
Campylobacter in reproductive tract
Recent work determined that it was possible to recover Campylobacter from all segments of the reproductive tract of broiler-breeder hens that are naturally exposed to feces that tested positive for Campylobacter. The digestive tract was clamped off and removed so the reproductive tract could be taken without accidental contamination. Once removed, the tract was aseptically sectioned into the infundibulum, magnum-isthmus, shell gland, vagina and cloaca (which are shared with the digestive tract). Each section was then tested for Campylobacter.
Campylobacter were recovered from all the segments of the reproductive tract except the infundibulum (Table 1). The level of Campylobacter in each segment ranged from fewer than 10 cells to several hundred per milliliter of sample.
The consistent recovery of Campylobacter from the cloaca of all of the commercial hens sampled and the high prevalence of recovery from segments of these hens’ reproductive tracts suggest that the presence of Campylobacter may be partially related to contact with litter.
Placing hens in wire cages, however, did not prevent Campylobacter colonization of broiler-breeder or layer hens. This is significant as the presence of Campylobacter within the reproductive tract of the hens could allow potential vertical transmission of Campylobacter from the hen through the egg to the broiler chick.
Likelihood of vertical transmission
In another study designed to evaluate the likelihood of vertical transmission, (that is transmission from hen through the egg to chick), 25% of the mature ovarian follicles were contaminated with naturally occurring Campylobacter. And, in the same group of broiler-breeder hens, 12% of the immature follicles had Campylobacter present in them also (Table 2).
Previous studies with Japanese quail made similar observations. In that study, the researchers suggested that Campylobacter may contaminate hatching eggs by either entering the vascular system and thereby invading the ovary and developing follicles or ascending the reproductive tract from the cloaca to colonize the oviduct.
These studies present very strong evidence that the reproductive tract and fertile egg are critical points for the entry of Campylobacter into breeder and broiler flocks as well as other types of fowl.
Naturally present in internal organs
To further complicate the issue, in our next study, Campylobacter spp. were found to be naturally present in a variety of organs including the thymus, spleen, liver, gallbladder and ceca of varying age breeder hens (Table 3).
Determining how and when Campylobacter infects these internal organs could provide important information in determining intervention strategies for reducing Campylobacter in broiler and broiler-breeder flocks. However, whether long-term reservoirs are established in these body organs and ultimately contribute to contamination of intestinal and reproductive tracts via these routes has not yet been determined.
Vertical transmission implicated
Research data can be confusing because even though egg transmission from the breeder flock has not been fully recognized as a source of entry, there is an abundance of research implicating vertical transmission as a means of contamination of a breeder flock, and subsequently, the broilers.
Campylobacter is not an easy organism to isolate and finding it in newly hatched chicks is difficult possibly because the number of cells is small or the microorganism enters into a state known as “viable but not culturable.” On the other hand, various researchers have clearly demonstrated that artificially inoculated eggs will result in chicks with Campylobacter in their intestines at hatch.
Campylobacter present in chicks
In another unique study, newly hatched chicks raised in a laboratory environment without exposure to any environment or possible source of Campylobacter became colonized. This along with other work strongly suggests that even though the organism usually cannot be isolated from the newly hatched chicks, Campylobacter are present in a significant number of chicks.
The various routes of egg contamination are still open to discussion. So, while we know a great deal about possible routes of contamination, there is much we do not know. In the meantime, control is only possible with a multiphase approach and does not ensure that poultry carcasses will be free from Campylobacter at processing.
N.A. Cox1, L. J. Richardson*, R. J. Buhr1, P. J. Fedorka-Cray1, and Y. Vizzier-Thaxton2
1 U. S. Department of Agriculture, Russell Research Center, Athens, GA 30605
2 Department of Poultry Science, Mississippi State University, Mississippi State, MS 39759
* Coca Cola, One Coca Cola Plaza, Atlanta, GA 30313