Paton, R. | Search bioRxiv

bioRxiv2020

A mathematical modelling approach to uncover factors influencing the spread of Campylobacter in a flock of chickens

Despite continued efforts into improving biosecurity protocol, Campylobacter continues to be detected in the majority of commercial chicken flocks across Europe. Using an extensive data set of Campylobacter prevalence within a chicken breeder flock for over a year, multiple Bayesian models are presented to explore the dynamics of the spread of Campylobacter in response to seasonal variation, species-specificity, bird health and total infection prevalence. It was found that birds within the flock varied greatly in their response to bacterial challenge, and that this phenomena had a large impact in the overall prevalence of different species of Campylobacter. Campylobacter jejuni appeared more frequently in the summer, while Campylobacter coli persisted for a longer duration, amplified by the most susceptible birds in the flock. Our study suggests that strains of Campylobacter that appear most frequently likely possess no demographic advantage, but are instead amplified due to the health of the birds that ingest it.

microbiology↗

bioRxiv2018

Differential effects of conspecific and heterospecific density on the development of Aedes aegypti and Aedes albopictus larvae

O_LIBetween-species competition shapes the distribution and abundance of populations. Aedes aegypti and Ae. albopictus are vectors of pathogens such as dengue and are known to compete at the larval stage.\nC_LIO_LIThe outcome of this inter-species competition has been found to be context dependent, with the strength and direction changing with resource availability and type. We were motivated by this uncertainty, and aimed to elucidate the magnitude and mechanism of competition.\nC_LIO_LIWe manipulated the larval density of mixed and single species cohorts of larvae, measuring the effects on survivorship and development time. Unlike other related studies, we adjusted the feeding regime so that the per-capita resource availability was kept constant across all density treatments, at a level sufficient for successful development. This ensured that each larvae at least had the opportunity to gain the requisite resources for pupation.\nC_LIO_LIOur analysis found that Ae. aegypti suffered notably less mortality due to intra- and interspecific competition. For both species, intra- and interspecific competition led to the survival of faster developing individuals, with the exception that slower developing Ae. albopictus larvae survived when exposed a combination of both high con- and heterospecific densities.\nC_LIO_LIThese results show that the competition between Ae. aegypti and Ae. albopictus can still occur even when resources are theoretically adequate for development. This suggests that larvae can alter resource seeking and consumption parameters when exposed to high densities of conspecifics and heterospecifics, leading to contest competition. Evidence for resource-independent mechanisms of competition such as crowding are also found, as is evidence for the importance of demographic stochasticity in population processes.\nC_LI

ecology↗