Infection connections: Badger surveillance project reveals how TB infects their social networks

By equipping more than 50 wild badgers with electronic ‘proximity collars’ that automatically tracked their social contacts, PhD Student Nicola Weber from the University of Exeter’s Centre for Ecology and Conservation built a network of contacts across the population and analysed patterns of infection. She found that TB-infected animals were less well-connected to their own groups than uninfected badgers, but at the same time infected individuals formed important links for the flow of infection between groups.

The research, which is published today in the journal Current Biology, suggests this unusual social arrangement may stabilise the spread of TB infection across the population.

Professor Robbie McDonald from the University of Exeter’s Environment and Sustainability Institute said: “This study has revealed an important link between social networks and TB infection. Infected animals were likely to be less important for spread within groups while at the same time being more important for spread between groups.

“Social stability is thought to mitigate disease spread, perhaps by maintaining the distinctive position of these individuals. Culling badgers perturbs social structures and we think our findings may help understanding of so-called ‘perturbation’, where culling has been linked to increases in TB in badgers.

“Curbing TB infection in wildlife remains a challenge. Vaccination has the potential to disrupt disease flow, without perturbing social network structures,” said McDonald.

Tuberculosis infection in cattle is a major animal health challenge in the UK and Ireland. In 2012, more than 8 million tests were conducted on cattle and 38,000 cattle were slaughtered to control TB. This testing and the resulting compensation are costly; controlling TB costs the UK taxpayer around £100m every year.

The study of the spread of disease through analysis of social networks has applications beyond badgers. The network analyses involved are similar to those used in people and so these techniques can be used to learn about how infection is transferred in a range of behaviourally complex hosts including humans, livestock and wildlife.

The work was conducted at the AHVLA’s National Wildlife Management Centre at Woodchester Park, Gloucestershire. The study was funded by the U.K. Department for Environment, Food and Rural Affairs (DEFRA).

The Environment and Sustainability Institute is working with businesses and enterprises across all sectors of the economy in Cornwall, the Isles of Scilly and beyond to translate research and expertise into innovative business practices, products and services in order to respond to the challenges of environmental change. It has been funded by the European Regional Development Fund Convergence Programme (£22.9M) and the South West Regional Development Agency (£6.6M), with significant support from the Higher Education Funding Council for England.

The paper is published in Current Biology: Badger social networks correlate with tuberculosis infection.