Relative abundance of Mycobacterium bovis molecular types in cattle: a simulation study of potential epidemiological drivers

Trewby, H., Wright, D. M., Skuce, R. A., McCormick, C., Mallon, T. R., Presho, E. L., Kao, R. R., Haydon, D. T. and Biek, R. (2017) Relative abundance of Mycobacterium bovis molecular types in cattle: a simulation study of potential epidemiological drivers. BMC Veterinary Research, 13, 268. (doi:10.1186/s12917-017-1190-5) (PMID:28830547) (PMCID:PMC5567634)

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Abstract

Background: The patterns of relative species abundance are commonly studied in ecology and epidemiology to provide insights into underlying dynamical processes. Molecular types (MVLA-types) of Mycobacterium bovis, the causal agent of bovine tuberculosis, are now routinely recorded in culture-confirmed bovine tuberculosis cases in Northern Ireland. In this study, we use ecological approaches and simulation modelling to investigate the distribution of relative abundances of MVLA-types and its potential drivers. We explore four biologically plausible hypotheses regarding the processes driving molecular type relative abundances: sampling and speciation; structuring of the pathogen population; historical changes in population size; and transmission heterogeneity (superspreading). Results: Northern Irish herd-level MVLA-type surveillance shows a right-skewed distribution of MVLA-types, with a small number of types present at very high frequencies and the majority of types very rare. We demonstrate that this skew is too extreme to be accounted for by simple neutral ecological processes. Simulation results indicate that the process of MVLA-type speciation and the manner in which the MVLA-typing loci were chosen in Northern Ireland cannot account for the observed skew. Similarly, we find that pathogen population structure, assuming for example a reservoir of infection in a separate host, would drive the relative abundance distribution in the opposite direction to that observed, generating more even abundances of molecular types. However, we find that historical increases in bovine tuberculosis prevalence and/or transmission heterogeneity (superspreading) are both capable of generating the skewed MVLA-type distribution, consistent with findings of previous work examining the distribution of molecular types in human tuberculosis. Conclusion: Although the distribution of MVLA-type abundances does not fit classical neutral predictions, our simulations show that increases in pathogen population size and/or superspreading are consistent with the pattern observed, even in the absence of selective pressures acting on the system.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Kao, Professor Rowland and Haydon, Professor Daniel and Trewby, Dr Hannah and Biek, Dr Roman
Authors: Trewby, H., Wright, D. M., Skuce, R. A., McCormick, C., Mallon, T. R., Presho, E. L., Kao, R. R., Haydon, D. T., and Biek, R.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Journal Name:BMC Veterinary Research
Publisher:BioMed Central
ISSN:1746-6148
ISSN (Online):1746-6148
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in BMC Veterinary Research 13: 268
Publisher Policy:Reproduced under a Creative Commons license

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
500191BBSRC Doctoral Training Grant 2009-15Massimo PalmariniBiotechnology and Biological Sciences Research Council (BBSRC)BB/F016786/1MVLS III - CENTRE FOR VIRUS RESEARCH