Future Risk of Bovine Tuberculosis (Mycobacterium bovis) Breakdown in Cattle Herds 2013-2018: A Dominance Analysis Approach.

Andrew W Byrne,Philip Breslin,Damien Barrett,Eoin Ryan,James O’Keeffe,Jamie M Madden

doi:10.3390/microorganisms9051004

Andrew W Byrne, Philip Breslin + Show 4 more

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https://doi.org/10.3390/microorganisms9051004

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Abstract

Bovine tuberculosis (bTB) remains a significant endemic pathogen of cattle herds, despite multi-decadal control programmes being in place in several countries. Understanding the risks of future bTB breakdown (BD) and the associated characteristics of herds and index breakdowns could help inform risk categorisation. Such risk categories could then contribute to tailored management and policies. Here, we estimated the future risk of herd BD for the cohort of herds that were derestricted during 2013 in Ireland using multivariable logit regression models, with a dominance analysis approach. One third of herds that were derestricted in 2013 experienced a breakdown during the follow-up five year period (1469/4459; 33%). BD length was a significant predictor of future risk, primarily driven by long BDs > 230 days relative to short BDs < 130 days (OR 95%CI: 1.157–1.851), as was having had a previous BD (OR 95%CI: 1.012–1.366). Herd-size was the dominant predictor of future risk (accounted for 46% of predicted variance), suggesting significant increase in risk of future breakdown with increasing (log) herd-size (OR 95%CI: 1.378–1.609). There was significant spatial variation in future risk across counties, and it was the second most dominant predictor of future risk (25% of predicted variance). The size of index breakdowns was not a strong predictor of future risk over a 5-year period. These findings can inform a risk-based policy development.

Highlights

The Mycobacterium tuberculosis complex (MTBC) includes Mycobacterium bovis, the causative agent of bovine tuberculosis
Our work has found that future risk is associated with characteristics of the index breakdown, though these features appear to explain limited variation in future risk based on dominance analysis
Previous work found that breakdown size in the index case could be a predictor of future bovine tuberculosis (bTB) risk in Ireland [42,43] and elsewhere (e.g., [18,20,44]); our non-significant result could relate to an improved follow-up on larger breakdowns, or it could be related to methodological differences between the studies

Summary

Introduction

The Mycobacterium tuberculosis complex (MTBC) includes Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB). Developing an evidential base for policy development and appropriate interventions is central to advancing effective programmes in countries that are actively trying to reduce, and eradicate, bovine tuberculosis in both their domestic stock and wildlife/environment [7,8,9,10]. One such country is Ireland, where bTB remains a priority endemic disease, affecting cattle herds [7,9,11]. Test-positive animals (known as ‘reactors’) are slaughtered, and trade/animal movement restrictions

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