Campylobacter contamination is a major threat to human health. It is commonly believed that the presence of the bacteria is restricted to the gastrointestinal tract in broilers. However, US research indicates that it can also be present in other internal organs, even in day-olds.
By N.A. Cox, L.J. Richardson, R.J. Buhr and P.J. Fedorka-Cray, USDA, Agricultural Research Service, Russell Research Centre, Athens, GA, USA
Campylobacter jejuni has become a major concern to the commercial poultry industry because the organism has been recognized as one of the more important causes of acute bacterial gastroenteritis in humans. Epidemiologic evidence has implicated raw poultry products as a signify cant source of this human infection. The infection in humans has been closely associated with the consumption of undercooked poultry, or the consumption of foods cross-contaminated from raw poultry products.
How, when, and to what extent Campylobacter is transferred between broiler breeder flocks and their progeny is not well understood because of the inability to routinely recover Campylobacter by culture in samples from hatcheries and from eggs of commercial operations. One potential mechanism for Campylobacter colonization in the birds could be that during hatching the bacteria are viable but nonculturable by current methods and enter a few of the hatchlings through one of many body openings and then disseminate to the lymphoid or internal tissues of the chick. Through molecular testing, Campylobacter has been found in the hatchery fluff , developing embryos, and newly hatched chicks. Recently, Campylobacter has been cultured from hatchery chick pads using a modified methodology procedure incorporating a pre-enrichment step. Campylobacter has been recovered in inoculated quail from the lung, liver, and spleen between day 7 and day 17 after oral inoculation. However, whether the dissemination was via the circulatory system or another route was not determined.
Dissemination to tissues and organs
A study was conducted to determine whether the dissemination of C. jejuni into various primary and secondary lymphoid organs occurs in young broiler chicks after oral and intracloacal inoculation. C. jejuni was isolated after oral inoculation from 13, 17, and 28% of the 1-hour, 1-day, and 1-week samples, respectively, and from 10, 8, 10, 25, and 40% of the thymus, spleen, liver/ gallbladder, bursa of Fabricius, and ceca samples, respectively (Table 1). Following the intracloacal route of inoculation, C. jejuni was recovered from 32, 8, and 16% of the 1-hour, 1-day, and 1-week samples, respectively, and from 5, 5, 5, 45, and 40% of the thymus, spleen, liver/gallbladder, bursa of Fabricius, and ceca samples, respectively. It is evident that dissemination of C. jejuni into several internal organs of an individual bird occurs after oral and intracloacal inoculation. For the orally inoculated groups, a specific sample site did not colonize more afterwards than another site one hour after inoculation, suggesting that dissemination occurs throughout the sites, but what role certain sites play in this movement of the organism will require additional research. For the cloacally inoculated groups, C. jejuni more readily colonized the ceca and the bursa of Fabricius than other sample sites, which was to be expected because the organism is entering the bird near these sample sites and because of the short period between inoculation and sampling. However, C. jejuni had disseminated to the thymus of one bird 1-hour after cloacal inoculation. The bacteria were also found in the bursa of Fabricius of that bird. Therefore, the lymphocytes or bursal cells in the bursa of Fabricius could have played a role in the rapid movement of C. jejuni to the thymus.
Presence in internal tissues
In a follow-up study, the objective was to determine if Campylobacter spp. could be recovered naturally from internal tissues of commercial broilers. Therefore, commercial broilers were screened to determine Campylobacter spp. Presence within spleen and liver/gallbladder (L/GB) along with ceca samples. Market-age (6- and 8-week-old) broilers were obtained from two commercial poultry processing plants at live haul and brought to the laboratory for analysis. A total of 52 6-week-old broilers and 80 8-week-old broilers were aseptically sampled. Overall, from the 6-week-old broilers, C. jejuni was found in 37, 37, and 50% of the L/GB, spleen and ceca, respectively (Table 2). Overall, from the 8-week-old broilers obtained from a separate commercial processing facility, C. jejuni was found in 4, 6, and 24% of the L/GB, spleens and ceca respectively (Table 3). As expected, Campylobacter incidence varied greatly between each visit. However, when birds were confirmed to be Campylobacter colonized by examination of the ceca, in many cases the organism was also recovered from spleen and L/GB samples.
Further understanding essential
The work discussed here demonstrates that C. jejuni can disseminate rapidly to the lymphoid organs of day-old broiler chicks following oral or intracloacal inoculation and persist in these sites for an extended duration. In addition, natural Campylobacter spp. can be recovered from the internal organs of market age commercial broilers. To date, many newly developed treatments focus on reducing or eliminating Campylobacter from the gastrointestinal tract of live birds and treatment efficacy is evaluated by elimination from the ceca. With these new findings, it may be important to consider whether these interventions are targeting the elimination of Campylobacter from internal tissue and organ sites along with elimination/reduction from the gastrointestinal tract. The main site for Campylobacter colonization is the gastrointestinal tract, however, depending on the treatment duration, latent recolonization could occur after treatment administration has subsided. These studies have only opened the door to numerous questions that need to be addressed and answered before Campylobacter ecology within birds can be fully elucidated. When, how, and whether Campylobacter naturally establishes reservoirs within particular tissues of birds is yet to be determined. A further understanding of avian immunology and the survival mechanisms Campylobacter uses to move throughout the birds body is essential for understanding Campylobacter ecology within birds, and therefore for the development of effective interventions. One goal is to determine whether systemic infection and/or long-term persistence in particular tissues of breeders contribute to Campylobacter dissemination to ovarian follicles ultimately resulting in colonization of the developing embryo and the broiler chick.