Inferring bovine tuberculosis transmission between cattle and badgers via the environment and risk mapping

You Chang; Nienke Hartemink; Andrew W Byrne; Eamonn Gormley; Guy McGrath; Jamie A Tratalos; Philip Breslin; Simon J More; Mart C M de Jong

doi:10.3389/fvets.2023.1233173

Inferring bovine tuberculosis transmission between cattle and badgers via the environment and risk mapping

Front Vet Sci. 2023 Sep 22:10:1233173. doi: 10.3389/fvets.2023.1233173. eCollection 2023.

Authors

You Chang¹, Nienke Hartemink^{1

2}, Andrew W Byrne³, Eamonn Gormley⁴, Guy McGrath⁵, Jamie A Tratalos⁵, Philip Breslin⁶, Simon J More⁵, Mart C M de Jong¹

Affiliations

¹ Quantitative Veterinary Epidemiology Group, Wageningen University and Research Centre, Wageningen, Netherlands.
² Biometris, Wageningen University and Research Centre, Wageningen, Netherlands.
³ One-Health and Welfare Scientific Support Unit, Department of Agriculture, Food and the Marine, National Disease Control Centre, Dublin, Ireland.
⁴ Tuberculosis Diagnostics and Immunology Research Centre, School of Agriculture, Food Science, and Veterinary Medicine, College of Life Sciences, University College Dublin, Dublin, Ireland.
⁵ Centre for Veterinary Epidemiology and Risk Analysis, School of Veterinary Medicine, University College Dublin, Belfield, Dublin, Ireland.
⁶ Ruminant Animal Health Division, Department of Agriculture, Food and the Marine, Dublin, Ireland.

Abstract

Bovine tuberculosis (bTB), caused by Mycobacterium bovis, is one of the most challenging and persistent health issues in many countries worldwide. In several countries, bTB control is complicated due to the presence of wildlife reservoirs of infection, i.e. European badger (Meles meles) in Ireland and the UK, which can transmit infection to cattle. However, a quantitative understanding of the role of cattle and badgers in bTB transmission is elusive, especially where there is spatial variation in relative density between badgers and cattle. Moreover, as these two species have infrequent direct contact, environmental transmission is likely to play a role, but the quantitative importance of the environment has not been assessed. Therefore, the objective of this study is to better understand bTB transmission between cattle and badgers via the environment in a spatially explicit context and to identify high-risk areas. We developed an environmental transmission model that incorporates both within-herd/territory transmission and between-species transmission, with the latter facilitated by badger territories overlapping with herd areas. Model parameters such as transmission rate parameters and the decay rate parameter of M. bovis were estimated by maximum likelihood estimation using infection data from badgers and cattle collected during a 4-year badger vaccination trial. Our estimation showed that the environment can play an important role in the transmission of bTB, with a half-life of M. bovis in the environment of around 177 days. Based on the estimated transmission rate parameters, we calculate the basic reproduction ratio (R) within a herd, which reveals how relative badger density dictates transmission. In addition, we simulated transmission in each small local area to generate a first between-herd R map that identifies high-risk areas.

Keywords: R map; bovine tuberculosis; domestic wildlife interface; environmental transmission; next-generation matrix method.

Grants and funding

This study was supported by the Irish Department of Agriculture, Food and the Marine's Research Funding Programme as part of the project Two host species transmission data analysis and modeling to calculate the risk maps for bovine Tb during eradication by badger vaccination in Ireland.