W.F. Jacobs-Reitsma

Quantifying Transmission of Campylobacter jejuni in Commercial Broiler Flocks

ABSTRACT Since meat from poultry colonized with Campylobacter spp. is a major cause of bacterial gastroenteritis, human exposure should be reduced by, among other things, prevention of colonization of broiler flocks. To obtain more insight into possible sources of introduction of Campylobacter into broiler flocks, it is essential to estimate the moment that the first bird in a flock is colonized. If the rate of transmission within a flock were known, such an estimate could be determined from the change in the prevalence of colonized birds in a flock over time. The aim of this study was to determine the rate of transmission of Campylobacter using field data gathered for 5 years for Australian broiler flocks. We used unique sampling data for 42 Campylobacter jejuni-colonized flocks and estimated the transmission rate, which is defined as the number of secondary infections caused by one colonized bird per day. The estimate was 2.37 ± 0.295 infections per infectious bird per day, which implies that in our study population colonized flocks consisting of 20,000 broilers would have an increase in within-flock prevalence to 95% within 4.4 to 7.2 days after colonization of the first broiler. Using Bayesian analysis, the moment of colonization of the first bird in a flock was estimated to be from 21 days of age onward in all flocks in the study. This study provides an important quantitative estimate of the rate of transmission of Campylobacter in broiler flocks, which could be helpful in future studies on the epidemiology of Campylobacter in the field.

Quantifying Transmission of Campylobacter spp. among Broilers

ABSTRACT Campylobacter species are frequently identified as a cause of human gastroenteritis, often from eating or mishandling contaminated poultry products. Quantitative knowledge of transmission of Campylobacter in broiler flocks is necessary, as this may help to determine the moment of introduction of Campylobacter in broiler flocks more precisely. The aim of this study was to determine the transmission rate parameter in broiler flocks. Four experiments were performed, each with four Campylobacter-inoculated chicks housed with 396 contact chicks per group. Colonization was monitored by regularly testing fecal samples for Campylobacter. A mathematical model was used to quantify the transmission rate, which was determined to be 1.04 new cases per colonized chick per day. This would imply that, for example, in a flock of 20,000 broilers, the prevalence of Campylobacter would increase from 5% to 95% within 6 days after Campylobacter introduction. The model and the estimated transmission rate parameter can be used to develop a suitable sampling scheme to determine transmission in commercial broiler flocks, to estimate whether control measures can reduce the transmission rate, or to estimate when Campylobacter was introduced into a colonized broiler flock on the basis of the time course of transmission in the flock.

Medium chain fatty acid feed supplementation reduces the probability of Campylobacter jejuni colonization in broilers

Campylobacteriosis in humans is associated with handling and consumption of contaminated broiler meat. Reduction of the number of Campylobacter-colonized broiler flocks could potentially be realized by decreasing their susceptibility for colonization. The aim of this study was to determine the effect of feed supplementation with a mixture of medium chain fatty acids (C(8)-C(12)) on susceptibility of broilers for Campylobacter colonization, feed conversion and body weight gain. Two experiments were carried out with individually housed commercial broilers. The birds were fed with medium chain fatty acids supplemented feed (n=227), or received feed without supplement (n=87). The birds were inoculated with a dose of Campylobacter jejuni varying between log(10)1.19-5.47 CFU. During 14 days after inoculation, cecal or fecal samples were collected, in which the presence of C. jejuni was determined by bacterial culture. Beta-binomial dose-response modeling of the colonization status at 14 days post-inoculation was performed to estimate the C. jejuni dose necessary to colonize 50% of inoculated broilers, which was estimated to be 200 times higher in broilers fed with supplemented feed (log(10)4.8 CFU) than in control broilers (log(10)2.5 CFU). Feed conversion was not affected by feed supplementation, while body weight gain was 49 g higher in broilers fed with supplemented feed. These findings indicate that susceptibility of broilers for Campylobacter colonization is decreased by supplementation with medium chain fatty acids, and that feed supplemented with this mixture may be a promising tool for the reduction of Campylobacter colonization in commercial broiler flocks.

Acidification of drinking water inhibits indirect transmission, but not direct transmission of Campylobacter between broilers.

In this study the effect of acidification of the drinking water of broiler chickens on both direct and indirect transmission of Campylobacter was evaluated. In the direct transmission experiment both susceptible and inoculated animals were housed together. In the indirect transmission experiment the susceptible animals were spatially separated from the inoculated animals and no direct animal to animal contact was possible. The transmission parameter β was estimated for the groups supplied with acidified drinking water and for the control groups. The results showed that acidification of the drinking water had no effect on direct transmission (β=3.7 day(-1) for both control and treatment). Indirect transmission however was influenced by acidification of the drinking water. A significant decrease in transmission was observed (p<0.05), with control vs. treatment point estimates being β=0.075 day(-1) vs. β=0.011 day(-1). Apart from providing quantitative estimations of both direct and indirect transmission of Campylobacter in broilers, this study also demonstrates the use of an experimental setup for indirect transmission of Campylobacter between broilers to assess the efficacy of candidate measures to reduce transmission.

Comparison of Campylobacter Levels in Crops and Ceca of Broilers at Slaughter

Abstract A considerable fraction of the poultry carcasses becomes contaminated with Campylobacter by cross-contamination from the digestive tract of colonized broilers at slaughter. Campylobacter in the crop may serve as a possible source of cross-contamination, because the crop may contain high numbers of Campylobacter and is more likely to rupture during the slaughtering process than intestines. In this study, the correlation between Campylobacter colonization levels in crop and cecum was assessed in 48 broilers of 31 days of age. In addition, the effect of drinking water supplemented with 0.2% volatile fatty acid (VFA) on these Campylobacter colonization levels was studied. No correlation between crop and cecal colonization levels was found (ρ  =  0.09; P  =  0.71), indicating that future studies on cross-contamination should include an examination of not only cecal colonization levels but also crop colonization levels. Supplementation of drinking water with VFA did not result in a significant reduction of colonization levels in either the crop (P  =  0.50) or the ceca (P  =  0.92), indicating that this is not an effective measure to reduce cross-contamination at slaughter.

Dose Response Characteristics of Campylobacter jejuni Colonization in the Embryonic Chicken Gut

Cultured micro-organisms form a vital cornerstone of all microbial research. With more than 500 biological resource centres worldwide, it may however become a daunting task to track down an interesting specimen of a given taxon (e.g. Campylobacter jejuni or Helicobacter pylori). Moreover, as biological research is inherently distributed in nature, with many researchers in different research institutes collecting data on the same organisms, knowledge generated on these microorganisms also has a tendency to become spread across the information jungle. As science and technology are moving rapidly, thereby increasingly making use of the scientific merits of previous research results, instant and effortless visibility of this creative and scientific downstream information has become imperative for the realization of successful innovation chains that take full opportunity of the exploitation of biological resources. The StrainInfo.net bioportal (www.StrainInfo.net) was established to stimulate this movement towards using multi-perspective integrated information in a broadened biological and clinical context. It brings together the biological material kept at multiple biological resource centres into a single portal interface, with direct pointers to the relevant information at the collections’ websites, and provides both historical traces and geographic distribution of the organisms they keep in culture. In addition, each organism is automatically linked to related sequences in the public domain and refers to all known scientific publications that deal with the organism. As the bioportal further unfolds itself as a helpful add-on to the microbiologists’ toolbox, we hope to gather around it a growing community of users that might become active contributors to both its content and implementation.

Estimation of moment of Introduction of Campylobacter spp. in commercial Broiler Flocks

Cultured micro-organisms form a vital cornerstone of all microbial research. With more than 500 biological resource centres worldwide, it may however become a daunting task to track down an interesting specimen of a given taxon (e.g. Campylobacter jejuni or Helicobacter pylori). Moreover, as biological research is inherently distributed in nature, with many researchers in different research institutes collecting data on the same organisms, knowledge generated on these microorganisms also has a tendency to become spread across the information jungle. As science and technology are moving rapidly, thereby increasingly making use of the scientific merits of previous research results, instant and effortless visibility of this creative and scientific downstream information has become imperative for the realization of successful innovation chains that take full opportunity of the exploitation of biological resources. The StrainInfo.net bioportal (www.StrainInfo.net) was established to stimulate this movement towards using multi-perspective integrated information in a broadened biological and clinical context. It brings together the biological material kept at multiple biological resource centres into a single portal interface, with direct pointers to the relevant information at the collections’ websites, and provides both historical traces and geographic distribution of the organisms they keep in culture. In addition, each organism is automatically linked to related sequences in the public domain and refers to all known scientific publications that deal with the organism. As the bioportal further unfolds itself as a helpful add-on to the microbiologists’ toolbox, we hope to gather around it a growing community of users that might become active contributors to both its content and implementation.