Rangitata TB came from West Coast

“All test-positive cattle have been slaughtered and were found to be infected with a West Coast strain,” it said in a letter to local farmers earlier this month.

“This confirms that the herds have become infected from bought-in TB infected cattle.”

TB Free last week told Rural News a thorough investigation into exactly where the infected cattle came from continues.

“The herd infections were no fault of the South Canterbury farmers. However, it remains vital that herdowners are aware of the TB status of any stock coming onto their property,” said a spokesman.

They could do that by calling 0800 4824636, he said.

A wildlife “survey” in the area caught 996 possums, all of which tested free of the disease. Final results on nine ferrets caught are pending.

TB Free national disease manager Kevin Crews last month told Rural News’ sister paper Dairy News that the maze of stock movements uncovered by investigations into recent cases, including those in Taranaki, Waikato and Northland, is prompting a rethink on testing protocols.

“The traceback is proving quite fraught in its complexity and [because of] the number of animals involved,” he said.

“It’s just the way the modern dairy industry operates with new conversions and herd expansions.”

Currently TB Free’s DNA testing can identify over 100 strains of the disease but complete genome sequencing, taking testing to a new level, could be routine within five years’ time, predicts Crews’ colleague Paul Livingstone.

Experimental use of such testing in Northern Ireland was reported at the Society of General Microbiology conference in Glasgow, Scotland, in August.

The results showed that, even on a scale of a few kilometres, TB samples from neighbouring farms were more closely genetically related than geographically distant farms linked by cattle movements.

In the UK context, the finding confirmed that while long distance spread via cattle movements plays a role, local transmission mechanisms appear to drive the spread of the disease.

Researchers were unable to determine what these local transmission mechanisms were, but UK native species the badger is frequently blamed. 

Principle investigator in the Northern Ireland work, Professor Rowland Kao, says he’s optimistic the approach will, in due course, finally determine what role, if any, the badger plays in transmission of the disease.

After years of protest from animal lovers and conservationists, but lobbying from agriculturalists, the English Government last year sanctioned a trial cull of badgers. 

The cull commenced earlier this year but has been labelled a farce for failing to meet the target 70% kill in the trial areas. An extension has been granted.