Tuesday, 25 June 2019 12:55

M. bovis doesn’t get worse than this

Written by  Nigel Malthus
John Roche. John Roche.

The chair of the Mycoplasma bovis strategic advisory group, MPI’s chief science adviser Dr John Roche, says he wouldn’t wish the disease on his worst enemy.

Roche has personal experience of M. bovis from a time when he was helping set up New Zealand-style dairy farms in the US with US partners. 

They gathered herds of cows into a seasonal calving system, effectively pooling the different herds’ diseases, and were then struck with flooding.

“So the physical stresses, along with the reduction in the immune system at calving, as well as mixing all these diseases, was the perfect storm.”

The result was “incredibly infectious” mastitis and high mortality in “incredibly sick” calves who caught the disease through the milk.

Roche said that three weeks into calving they had to cull a fifth of the herd and then step into long-term management with regular testing and regular culling to keep on top of the disease.

“People say you can manage the disease. Generally the people who say that haven’t dealt with it in a seasonal calving system and don’t really understand the peculiarities of the NZ system.”

Roche said something he loves about NZ is how a young person “almost without a penny to their name but with the smarts and a hard work ethic” can become an asset multimillionaire in 10 to 15 years. That was a New Zealand icon and hallmark of our system.

“That would all have to cease if we went to long-term management. It would be too difficult to manage the biosecurity implications.

“I think the [agriculture] minister and Prime Minster and the industry partners made a very brave decision to eradicate but I’m certainly 100% behind it.”

MPI, with DairyNZ and Beef + Lamb NZ, has called for proposals from scientists in NZ and elsewhere to research new diagnostics as outlined in the Mycoplasma bovis science plan.

Speaking shortly before the deadline for proposal submission, Roche was unable to say how many had been received. But at least 72 organisations had downloaded the documents “which gives us great confidence that there’s a lot of people internationally and domestically very interested”.

He recently spoke with a couple of groups with “really good” ideas on ways to improve testing for the disease.

Roche said MPI is looking in three main areas, the first being improving current testing.

“[Many] people talking in the media and elsewhere say our tests aren’t good tests. They are, but are dealing with a very challenging bacteria,” he said.

But there are probably ways to improve sampling or extraction methods or laboratory methodology.

Secondly, MPI is hoping for new and more sensitive tests to detect the bacteria before it begins shedding in an infected animal.

Pathway to new test

As one example of a potential pathway to a new test, John Roche said he had worked with a PhD student looking at how tissues in the body gave off nanoparticles which travelled through the blood, effectively acting as messengers telling other tissues “how they’re feeling”. 

Such particles are now being looked at in human cancer research. The student had shown them associated with liver stress in cows.

The third testing possibility MPI is looking at is to improve testing of imported germplasm to help prevent reinfection.

“It’s a really low risk pathway but we want to close down as many potential loopholes as possible,” said Roche.

Proposals will be evaluated by an evaluation panel, who will make recommendations to the M. bovis governance board for approval of funding. Contract negotiations will then follow.

Roche said any improvements to current methodology could hopefully be adopted within the next 12 months, but “some of the gems that will help us finally eradicate the disease, they’re probably three or four years in the making”.

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