Bovine TB: genetic contact tracing could help control outbreaks

The use of genetic contact tracing to identify the source of a bovine tuberculosis (TB) outbreak could signal a new approach in managing the disease, according to a study published in the Journal of Applied Ecology.

In response to a rise in TB rates among wildlife in the eastern part of the county of Cumbria (north-west England) with no previous infections, researchers examined the DNA of Mycobacterium bovis isolates from cows and badgers that had tested positive. All isolates were found to be closely related to each other, pointing to a single purchase of cattle as the most likely source of infection.

Experts from the Universities of Edinburgh and York, University College Dublin, and the UK Animal and Plant Health Agency developed a method of tracking the outbreak by integrating genetic data with spatial locations and contact tracing. This allowed them to compare small changes in the DNA as it spread from one animal to the next.

The outbreak began with an infected cow brought to a farm in the region from Northern Ireland, according to the research. Disease passed among cattle, infecting an increasing number of cows, then spread throughout the local badger population, before being passed back to cows in a cycle of infection.

The researchers suggest that their approach is an effective way to model the spread of infectious disease, and might be applied to understand the complex spread patterns of other diseases.

Article: Rossi, G., Crispell, J., Brough, T., Lycett, S. J., White, P. C. L., Allen, A., Ellis, R. J., Gordon, S. V., Harwood, R., Palkopoulou, E., Presho, E. L., Skuce, R., Smith, G. C., Kao, R. R. (2021). Phylodynamic analysis of an emergent Mycobacterium bovis outbreak in an area with no previously known wildlife infections. Journal or Applied Ecology, (Early View, 1 November 2021), doi: 10.1111/1365-2664.14046

[SOURCE: University of Edinburgh]