Campylobacter jejuni colonization and transmission in broiler chickens: a modelling perspective

Abstract

Campylobacter jejuni is one of the most common causes of acute enteritis in the developed world. The consumption of contaminated poultry, where C. jejuni is believed to be a commensal organism, is a major risk factor. However, the dynamics of this colonization process in commercially reared chickens is still poorly understood. Quantification of these dynamics of infection at an individual level is vital to understand transmission within populations and formulate new control strategies. There are multiple potential routes of introduction of C. jejuni into a commercial flock. Introduction is followed by a rapid increase in environmental levels of C. jejuni and the level of colonization of individual broilers. Recent experimental and epidemiological evidence suggest that the celerity of this process could be masking a complex pattern of colonization and extinction of bacterial strains within individual hosts. Despite the rapidity of colonization, experimental transmission studies exhibit a highly variable and unexplained delay time in the initial stages of the process. We review past models of transmission of C. jejuni in broilers and consider simple modifications, motivated by the plausible biological mechanisms of clearance and latency, which could account for this delay. We show how simple mathematical models can be used to guide the focus of experimental studies by providing testable predications based on our hypotheses. We conclude by suggesting that competition experiments could be used to further understand the dynamics and mechanisms underlying the colonization process. The population models for such competition processes have been extensively studied in other ecological and evolutionary contexts. However, C. jejuni can potentially adapt phenotypically through phase variation in gene expression, leading to unification of ecological and evolutionary time-scales. For a theoretician, the colonization dynamics of C. jejuni offer an experimental system to explore these ‘phylodynamics’, the synthesis of population dynamics and evolutionary biology.

Investigation of the Presence and Protective Effects of Maternal Antibodies Against Campylobacter jejuni in Chickens

“…Because breeding flocks will almost certainly have repeated exposures to Campylobacter, probably with multiple strains of varying serotypes, it seems likely that antibody levels will vary, not only among laying flocks but also among hens within a flock. This may contribute to the variability in susceptibility and outcome of challenge among chickens in experimental challenge models (8,16) and the susceptibility of individual birds within commercial flocks. It may also contribute to the variation in response of birds to vaccination against Campylobacter that was reported by several speakers at the Med-Vet-Net Workpackage 34 Workshop on Immunity to and Vaccination Against Campylobacter in Chicken (March 2009, Veterinary Laboratories Agency, Addlestone, Surrey, United Kingdom).…”

Dynamics of Dual Infection with Campylobacter jejuni Strains in Chickens Reveals Distinct Strain-to-Strain Variation in Infection Ecology

“…Other studies have shown that birds are able to clear Campylobacter (32), and competition between strains may be an important mechanism leading to clearance of a strain (33). Fur-ther work would be needed to confirm whether the two strains do in fact have different niches within the gastrointestinal tract or whether, at earlier time points, C. jejuni M1 is found higher up the gastrointestinal tract.…”

Campylobacter biofilm phenotype exhibits reduced colonization potential in young chickens and altered in vitro virulence

“…Epidemiological studies have been undertaken to identify risk factors and determine sources of infection. Poor cleaning, biosecurity breaches, poor poultry house maintenance, short empty periods, insects, and the presence of other animals on the farm have all been suggested as risk factors (Conlan et al, 2007). Detecting sources of Campylobacter infection to flocks may be difficult and, due to the susceptibilities and highly fastidious nature of C. jejuni, carry-over between flocks is difficult to explain (Newell and Fearnley, 2003).…”