TB genome work aids tracing

Researchers from the University of Glasgow, working in collaboration with the Agri-Food and Biosciences Institute and the Department of Agriculture and Rural Development, Northern Ireland, sequenced the genomes of 147  million samples of the bacteria responsible for bovine TB, mycobacterium bovis (M. bovis).

The samples came from a decade of outbreaks in Northern Ireland. By combining the genomic sequences of the bacteria with information about when and where the samples were isolated, and stock movement data, researchers were able to build a detailed forensic map of the disease’s spread.

The results show that, even over a few kilometres, M. bovis samples from neighbouring farms were more closely genetically related than those geographically distant on farms which had had cattle moved between them.

The finding confirms that, while long distance spread via cattle movements plays a role, local transmission mechanisms appear to drive the spread of the disease, although the researchers are unable to determine what these are at the present time.

“The inclusion of whole genome information in our data will give us unprecedented insight into how bovine TB spreads, and will help us to develop better control methods for the disease,” says one of the paper’s authors, Hannah Trewby.

Crucially, it will help clarify the role UK native species the badger plays in spreading the disease, and which, after many years of lobbying from farming organisations, the UK Government finally, but controversially, agreed to allow a limited cull of, starting this year.

Professor Rowland Kao, the Principle Investigator of the project, says the Northern Ireland results suggest establishment and local persistence of the pathogen in cattle has a distinct spatial signature.

“We believe that explaining this signature is the key to quantifying the role that badgers play…. While we do not yet have sufficient data to be definitive, it is clear that whole genome sequencing of the bacterium will play an important part in solving this puzzle.”

It should also be a relatively inexpensive way to track TB, farm to farm.

“Given the extensive collection of samples already collected from cattle and badgers, we are optimistic that this approach will help accumulating the right scientific evidence over the coming years to tackle this important problem.”

Rural News invited TBfree New Zealand to comment on this work and what benefit there might be in tracing the disease here, but it was unable to respond before this article went to press.