Keith Woodford explains how the arrival date of Mycoplasma bovis in New Zealand is crucial to the eradication prospects

By Keith Woodford*

A key question for MPI and Government to address is how long has Mycoplasma bovis been in New Zealand. The answer to that question, together with MPI’s capacity to upscale their operational capacity, will largely determine whether or not eradication is going to be successful.

If, as the Government now believes, Mycoplasma bovis first arrived here around December 2015 or January 2016 on the Zeestraten property in Southland, then it is reasonable to hope but not necessarily expect that the eradication program will be successful.  But if it was here prior to that, then eradication becomes an increasingly long shot.

Another way of describing it is that, in the battle between Mycoplasma and MPI, it is the head-start that counts. For each year that the disease has been here, there will have been an exponential spread of the little stealth bombers.

MPI is saying their belief it was not here prior to December 2015 is based on the genetic tracing they have done. In contrast, I am saying that empirical evidence, albeit with some hindsight, suggests it was here before then.

The genetic tracing that MPI has been doing has come from infected herds which provide the source of samples for their microbiologists to test.

The associated problem with the MPI position is that they have only been tracing animal movements for 2016 and 2017. So, anything prior to that will have escaped their net. That provides circularity to their argument.

Accordingly, when interpreting MPI statements, it is important to differentiate between MPI saying it ‘has no evidence’ in relation to a specific situation, and that situation not existing. If they have not looked, then they do indeed have no evidence.

In this article, my focus is on the possibility that the Zeestraten farms were infected before the end of 2015, with one or two years prior to that being most likely.  There is a further possibility that Mycoplasma bovis has been present elsewhere in New Zealand for many years. But the evidence for and against that possibility is too big a topic to include in this article. Should that possibility be correct, then it simply reinforces what is written below.

The Mycoplasma bovis cultures undertaken by MPI indicate the organism has mutated on one occasion from anything recorded elsewhere. What we don’t know is whether or not that mutation occurred in New Zealand or overseas. All we know is that at least by early 2016, the dominant organism in the current outbreak was in its current genetic form.

What MPI is saying is that it would have expected the organism to have shown more genetic diversity if it had been here longer. That is a tenuous argument. Bacteria can reproduce every twenty minutes or less, and hence there is great scope for mutations to occur. But for a mutation to survive and then dominate within the Mycoplasma bovis population, it has to have a competitive survival advantage relative to its predecessor variant. Successful mutations are driven by random chance.

I have asked Minister Damien O’Connor for permission to talk to the scientist who supposedly made this particular judgement about how long Mycoplasma bovis has been here. I would love to know the caveats that scientist placed on his or her own judgement. My experience with other science issues is that once messages pass up the management chain the caveats often get left off.   Permission to talk to the scientist has not come through.

My scepticism is fuelled by three issues.  One of these is the track record of MPI. The second is empirical evidence of calves dying between 2014 and 2016. The third is that some of the supposed animal traces involve a ‘long bow’, with the possibility that other explanations related to previous animal movements may be more likely.

Back in 2017 and through until April 2018, MPI was insistent that the initial infection occurred in 2017. I have correspondence showing that.  In contrast, within three weeks of the outbreak I was writing about the possibility the Van Leeuwen farms were not the original New Zealand source, hence the need for back tracing as well as forward tracing.

 I came to those conclusions through a simple process of deductive logic. But it was not until April 2018 that MPI conceded that the Zeestraten outbreak pre-dated the South Canterbury outbreak, and even then they initially muddled that message. So MPI has the capacity to get these things horribly wrong.

If MPI had not got that so wrong, then Mycoplasma bovis would have had less of a head-start.

More recently, MPI Biosecurity Head has been reported as saying that MPI is using carbon dating to trace the date of the outbreak. What probably started as a poor analogy by the scientist to explain genetic time-clocks, which are nowhere near as precise as carbon dating, somehow got emasculated by non-scientists to become that carbon dating was being used. This is nonsense, as carbon dating only tells the time that carbon has been in a dead plant or animal. Let’s be clear: genetic time-clocks can run both very fast and very slow, depending on circumstances. 

It is always easier to see things with hindsight, although collecting hard evidence for historical events can be very challenging. However, there is consistency to reports I am hearing of people who had bad experiences in 2014 and 2015 with calves that either came from the Zeestratems or had been in a mob with such calves. It is important to recognise that the Zeestraten calf-raising enterprise was very substantial, with many thousands raised each year.

Within the Van Leeuwen Group, they had one farm which had two-year old cattle with no access to other cattle within the wider Van Leeuwen group since being calves. But there were some other animals in this group that came originally from Zeestraten farms and these arrived mid 2017. The pattern of antibody blood tests provides evidence that the infection on this particular farm probably came in with these introduced animals, and the likelihood, given that they had been out of Southland in Central Otago for most of their lives, is that they themselves got infected as calves while still in Southland back in mid 2015.

Now, this is not conclusive proof, but it is a strong indicator that MPI needs to be working on the possibility of the infection being well established on the Zeestraten farms by the time these calves were born. And that means that the cows providing the milk for these calves had themselves become infected even earlier.

This is just one of multiple examples that I could provide, none of which by itself gives conclusive proof, but all of which point in a particular direction.

One of the interesting case studies, albeit for calves born in 2016, is of Susan McEwen from Palmerston in Otago. Susan has given interviews for RNZ Checkpoint and an RNZ Insight documentary.

Susan McEwen raised some 3000 calves each year through grazing contracts from when the animals were four days of age through to 100kg of weight. In 2016, she lost 600 calves from illness, which could not be diagnosed at the time by either her or her vets. With hindsight, and now knowing the symptoms, this was almost certainly Mycoplasma bovis. 

A key issue is what happened to all the surviving calves from the McEwen property. Susan has stated that she believes they were dispersed widely across New Zealand. The grazing company says they were all subsequently slaughtered for beef. But who would really know, as MPI have only just got onto this one. It would be remarkable if every animal has been slaughtered. In the meantime,  who did they mingle with?

Currently, MPI asks in their latest stakeholder update (Number 90) for people receiving calves from the Zeestratens after the start of January 2016 to contact them. What about prior to 2016? 

MPI justifies its position by answering its own rhetorical question as to how “we know when it arrived”.  Their answer (with italics added by me) is that genetic tracing “indicates the New Zealand strain likely entered the country in late 2015 or early 2016. Based on current knowledge the genetic clock shows no evidence of the disease arriving before this date.” Note their choice of specific words which I have italicised, which have probably originated with the scientists. But then the policy folk have acted as if these indications based on specific assumptions were certainties.

This conversion of uncertainty to certainty is common as messages move from scientists to non-scientist managers. In previous writings I have used the example from Fonterra’s botulism scare where AgResearch told Fonterra that the initial test results were consistent with a diagnosis that there could be botulism in the milk powder but that more testing was needed. As the message was passed up the chain. it became that there was botulism in the milk powder. The details of this saga were laid out eventually in the independent report to Government, but hardly anyone has read it.

In humorous vein, I am reminded of the hypocryphal example where the army captain sent a message back to headquarters to ‘send reinforcements, we are going to advance’. By the time it got to the general, it had become ‘send three and four pence, we are going to a dance’.

Unfortunately, there is no humour when it comes to Mycoplasma bovis. However, there is a big lesson to be learned. It is that policy makers and bureaucracies thrive on certainty, and often lack skill in dealing with scientific uncertainties. In similar vein, I see a parallel with Steve Hansen’s comment in recent days that the big lesson from losing to France at the Rugby World Cup back in 2007 had been to have contingency plans for all scenarios.

*Keith Woodford was Professor of Farm Management and Agribusiness at Lincoln University for 15 years through to 2015. He is now Principal Consultant at AgriFood Systems Ltd.   His articles are archived at http://keithwoodford.wordpress.com. You can contact him directly here.