We study the epidemiology of tuberculosis in wild badgers using a combination of fieldwork, laboratory investigations and long-term data analysis.

badger in grass field

Challenge

Tuberculosis (TB) occurs worldwide and affects many animals (farmed and wild) as well as humans. In cattle, TB is caused by infection with the bacterium Mycobacterium bovis and is sometimes referred to as bovine TB. Eradication in parts of the UK and Ireland is hindered by transmission of M. bovis between cattle and European badgers (Meles meles). Diagnostic tests in badgers are of limited accuracy but may help us understand and predict disease progression. In collaboration with colleagues at the Animal and Plant Health Agency, we conduct field studies of TB epidemiology and analyse long-term datasets to gain insights into the diagnosis and progression of the disease in badgers.

The aims of our research are to:

1. Determine the accuracy of currently available tests for TB in badgers, which may be used on their own or in combination with other tests.
2. Identify better (novel) ways of using these tests to increase the accuracy of diagnosis at both the individual badger and social group level.
3. Make this new information available so it may be used to inform:

    1. Management strategies for controlling TB in badgers.
    2. Research studies which aim to better understand the epidemiology of the infection in badgers.

Solution

Our research combines ecological and epidemiological data to improve diagnosis and inform control of TB in badger populations. We use a range of advanced statistical techniques and analytical methods on long-term data collected from wild badgers that have been tested for TB using a variety of diagnostic tests. We do this by:

- Interpreting in combination diagnostic tests that are based on identifying different markers of infection (different arms of the immune system)
- Accounting for biological changes that occur in response to infection and their time dependency
- Using all information available at population and individual badger level to model epidemiological processes over time, often using probability-based approaches
- Employing mathematical methods to examine the potential impact of a range of interventions that might be employed to try to reduce levels of TB

tuberculosis bacterium

Impact

One of our key areas of focus is looking at changes in TB in the badger population over time. We ask (and answer) such questions as:

1. How likely (and over what timespan) is a badger that tests positive for TB to go on to become infectious to others?
2. How do results from different diagnostic tests compare?
3. How many badgers do we need to sample to be confident of detecting TB if it is present, and how does this change with prevalence?
4. Are infected badgers more or less likely to be captured again in the future?

Our work demonstrates the value of long-term data collection. The Woodchester Park study has been collecting data from badgers since 1976. This allows us to look at how TB progresses within individual badgers, in generations of social groups, as well as broader population-level effects.

Our findings are widely published and shared with Defra—so they are available to inform management strategies to better control TB, and research studies which aim to better understand the epidemiology of the infection in badgers.

Partners

We collaborate with colleagues at the Animal and Plant Health Agency. Some of our research is funded by Department for the Environment, Food & Rural Affairs (Defra).

Title Publication Year
Serologic responses correlate with current but not future bacterial shedding in badgers naturally infected with Mycobacterium bovis Transboundary and Emerging Diseases 2021
Quantifying and addressing bias associated with imperfect observation processes in epidemiological studies Frontiers in Veterinary Science 2019
Quantifying direct and indirect contacts for the potential transmission of infection between species using a multilayer contact network Behaviour 2018

Inference of the infection status of individuals using longitudinal testing data from cryptic populations: Towards a probabilistic approach to diagnosis

Scientific Reports

2017

Quantitative interferon-gamma responses predict future disease progression in badgers naturally infected with Mycobacterium bovis

Epidemiology and Infection 2017
Diagnosis of tuberculosis in groups of badgers: An exploration of the impact of trapping efficiency, infection prevalence and the use of multiple tests Epidemiology and Infection 2016
Epidemiology of Mycobacterium bovis Zoonotic Tuberculosis (3rd ed) 2014
Molecular epidemiology of Mycobacterium bovis Zoonotic Tuberculosis (3rd ed) 2014
Patterns of direct and indirect contact among cattle and badgers naturally infected with tuberculosis Epidemiology and Infection 2013
Performance of proximity loggers in recording intra- and interspecies interactions: a laboratory and field-based validation study PLoS ONE 2012
Diagnostic accuracy and optimal use of three tests for tuberculosis in live badgers PLoS ONE 2010

 

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