Keith Woodford discusses outcomes and strategies for controlling Mycoplasma bovis

Keith Woodford discusses outcomes and strategies for controlling Mycoplasma bovis

By Keith Woodford*

It now seems likely that Mycoplasma bovis is in New Zealand to stay. Just like the rest of the world, we must learn how to live with it. We do not yet have to give up totally on hopes of eradication, but eradication is looking more and more unlikely.

The control program has suffered from incorrect information and poor communication, and there is much to be learned from that. These information flaws have affected farmer and public attitudes. In some cases, this has created additional and unnecessary stress, and unfair criticism of individuals.

However, the probability is that these flaws have not affected the success or failure of the eradication program. The chances are that Mycoplasma bovis has been here for some years, in which case eradication was always going to be impossible.

The starting point for moving forward is for MPI (the Ministry of Primary Industries) to provide more transparency about the current situation. MPI has consistently stated that all infected farms have a link to the Van Leeuwen Group via animal movements, but that no longer stands up well to scrutiny. 

The problem may well be that admitting that evidential links do not exist between newly identified infected farms and the Van Leeuwen Group would be a clear admission that, in terms of eradication, the horse has bolted. And MPI is not yet quite ready for any such admission.

Aad Van Leeuwen tells me that he is totally baffled by the MPI claims that these links exist. And he has failed in his attempts to get MPI to define those links.

In the case of the infected Hawke's Bay farm, it is indeed correct that a previous Van Leeuwen sharemilker sold animals to that Hawke's Bay farm. But the Van Leeuwen sharemilker's herd that those animals came from (now owned by the Van Leeuwen group; i.e., no longer owned by the sharemilker) has been tested five times and has tested clean each time. It is no longer a restricted herd. 

So, the likelihood is that it has been the additional testing scrutiny that the Hawke's Bay farm has been put under (because of those animal movements) that has led to the positive findings, but that these animals were not actually the source. In that case, no one knows how it got to the Hawke's Bay herd. Without the particular scrutiny this farm was put under, the presence of the organism would probably have gone undetected.

In the case of the Southland infections on the Zeestraten farms, it is correct that the Van Leeuwens and the Zeestratens know each other.  But there is no evidence of animal movements between the two groups of farms.

It is also increasingly unlikely that there are direct links between the Van Leeuwens and some of the other South Canterbury infected properties. One such property is close to a Van Leeuwen farm but is separated by a road and a 20-metre flood channel. And in any case, that particular Van Leeuwen property has also been tested multiple times and been declared free of infection.

There is yet another South Canterbury property that has tested positive but MPI has given no publicity to that fact. Rather, they have advised Aad Van Leeuwen (I have seen the correspondence) that “we are generally not reporting new detections unless there is something of significance or public interest”.

I think most farmers would like to be informed about another farm being found positive rather than having to rely on MPI’s judgment as to whether having that knowledge was in their interests, or alternatively having to rely on the bush telegraph. And this particular farm is indeed linked to multiple other farms throughout New Zealand, although MPI says they think all links were prior to the risk period. But none of us actually know when the risk period started, because we don’t know when or how that farm was infected.

There are also other infected farms, such as the Ashburton farm, for which links to the Van Leeuwen group have not been defined.

It is now becoming increasingly likely that the Van Leeuwen farms were not the first to be infected. Rather, because of a particularly diligent veterinarian, they were the first to be identified. And that perspective changes everything in terms of the practicality of national eradication.

In previous articles [here and here], I have focused on live imports and semen as the most likely original source. But now I am giving increasing weight to the possibility that it may have come in from imported embryos. Regardless, the Van Leeuwens did not import live animals, semen or embryos. Accordingly, it was always hard to see how they could be the original source.

So, if Mycoplasma bovis is here to stay - and all of us surely still hope that it is not - then how do we manage it?

Once again there are no simple answers. I have been reading up on the available information that I can find in the international literature, but it is confusing, and not helped by the absence of simple reliable tests for the organism. This Mycoplama bovis is indeed a tricky little devil with great ability to hide.

For farmers, there are three key questions. The first is what should they do to minimise the chance of infection? The second is what are the signs that they may have Mycoplasma bovis? The third is what should they do if they do get an infection?

The answer to the first question is easy in theory but difficult in practice. It requires running closed herds without purchase of animals. It also means strict hygiene procedures are needed for farm service people who move between farms. Livestock trucks will need to be cleaned thoroughly between jobs involving inter-farm transfers. 

In practice, running totally closed herds is not an option for most farmers, but the other two sets of procedures are more practical. There will continue to be animal movements between farms and that will be the main way by which the disease spreads.

Our dairy systems have developed on the premise that all herds have good fundamental health status and that animals can be safely bought and sold. But the evidence for that has always been fragile. One only has to think of Johnes disease (pronounced Yo-knees), which is an infective disease endemic in many herds. 

Farmers will need to give a lot more thought about young stock being raised away from the home farm (as occurs currently on probably most farms) and also about off-farm wintering of cows (as is particularly common in the South Island).

The key first indicator of Mycoplasma bovis in lactating cows is likely to be mastitis in multiple quarters of the udder rather than a single quarter, combined with non-response to antibiotics. This may or may not be combined with arthritic joints. In many cases there will be no symptoms, but the animal will still be infected and may be capable of transmitting to other animals. Even when there are suspicious symptoms, it may not necessarily be Mycoplasma bovis.

In young stock, the first symptoms are likely to be respiratory issues and arthritis.

The question of what to do when an infection is found is vexing. Once symptoms are evident, then the outlook for full recovery is bleak. These animals should be quarantined immediately and, at least for lactating cows, then culled. But that is unlikely to result in a clean herd, because there may also be infected animals present that show no symptoms. Over time, antibody levels in the herd and hence disease resistance will probably increase, but calves will remain susceptible.

Ensuring all newborn calves receive good quality pasteurised colostrum rather than fresh from the mother cow will be important in any herd that does have Mycoplasma bovis.

The other key insight from literature is that the likelihood of an outbreak of Mycoplasma bovis symptoms is more likely when animals are under stress. This could be related to bad weather, insufficient feed, unclean housing, proximity to calving, or the presence of some other disease factor, with Mycoplasma bovis symptoms developing as a secondary disease.

If there is one ray of good news out there, it is that dairy industries in other countries do manage to prosper despite having Mycoplasma bovis.  If eradication is not possible, then we will, over time, learn how to manage the disease under our New Zealand conditions. Mycoplasma bovis will continue to be a big nuisance, and some farms will be hard hit, but it is not going to destroy the industry.


*Keith Woodford is an independent consultant who holds honorary positions as Professor of Agri-Food Systems at Lincoln University and Senior Research Fellow at the Contemporary China Research Centre at Victoria University.  His articles are archived at http://keithwoodford.wordpress.com. You can contact him directly here.

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16 Comments

How does the thinking in MPI be adjusted?
Collectively their performance has been seen as disappointing! And not a proud performance in Methven last week. More leaning on/drawing on the goodwill of the good folk in the audience to show a brave face.

IN Otago/Southland Fonterra is helping to coordinate MPI's milk testing of herds for M Bovis. The programme will involve testing three milk samples from every dairy farm. One sample will be taken from bulk milk as part of the regular sampling process at milk collection. There is also a requirement for a separate milk testing regime of sick cows.

MPI has decided to extend this regional programme to a National surveillance programme. Hopefully we will see in the coming months the extent to which this disease exists and a rational strategy for dealing with it, emerge.

I understand that milk testing is the most accurate way to find m bovis infections, but am happy to be corrected on it.

Regardless of who had the disease first, were stock (bobby calves for rearing) sold from herds within the VLG without the required NAIT tags in their ears? Were all the basic legal requirements followed that a seller of stock has to adhere to.

How is the relationship between the VLG and their sharemilkers going?Is there a plan in place to secure their futures? Is MPI able to assist? As yet, Not much is being said about this in your discussions with VLG.

These are some of the issues raised by locals that may be need to be addressed publically by the VLG

Bruadar
These are all valid and important questions.
My current understanding is that the stock movements from the VLG were all recorded and that initial tracing from the VLG group has not been a constraint to the control and eradication program. However, perhaps this was not always the case for subsequent stock movements via traders etc, for which those traders are responsible.
On the other issues, I am cautious of making any statements given the importance of getting all sides to the story, and the need to be sure of my facts.
KeithW

NAIT is a giant screw up. The good news is, it's soon to be replaced by blockchain soon.

https://www.ted.com/talks/bettina_warburg_how_the_blockchain_will_radica...

MPI do a good job for the underfunding they get from Government. I feel sorry for the animal welfare officers that get burnout trying to deal with the number of calls they get from people on animal welfare. There are only 15 animal welfare officers in New Zealand MPI and big companies like Fonterra rely on these 15 people to police their 10,000 farms - what a joke

But NAIT should be simple, if you have a big enough data base. We have Chilean needle grass around here, looks like that battle is lost, far more serious is the stink bugs turning up in pheromone traps.

Eek. Needlegrass is horrendous. I have seen that stuff down Seddon. Whats up with the stink bugs Aj? Nait is a work in progress. I borrowed a reader to move some cattle. Turns out you needed a degree in computing to manage the transfer. I ended up manually writing the numbers down. Musta been 15 numbers per animal. And there was something like 60 odd animals. It took patience.

C'mon Belle, NAIT is not a work in progress - it's been going since 2009 ;-) I know a farmer who bought a herd of cows for this season. According to NAIT approx 10% of his herd that he should have he doesn't and 10% of his herd that he does have, he shouldn't. 7 months later he is still battling to get it sorted out. If there is a 10% data entry error on the NAIT database thats more than half a million stock misrecorded. I still hear farmers say they sent stock to the works with tags and on ocassion (recently) have been told some had no NAIT tags - so incur a fee - is there a scam going on here?

When is NZ going to recognise that the NAIT system is a failure?

It's nothing but a huge costly nonsense. And I bet those staff keep advising their Minister that its all fine and dandy which makes me think they are deliberately misadvising their Minister!

well the meat companies wanted it but didn't want to pay for it. So the government launched it on behalf of the farmers who pay for it via levies.
I think the aim is to just carry on regardless, it looks good, we have traceability, of course we do it's called NAIT.

I purchased 35 cattle, all on sellers Nait, when they turned up only 34 turned up on Nait site, I rang seller he did everything right. So I rang NAIT, darn it bull didn't exist, but I had it walking around the bloody paddock. So i tried to register its tag but of course it had already been registered. It's a monumental screw up, some days %10 of cattle at saleyards fail to track and they want to include sheep!

With the out break in Canterbury we had cattle from the area being trucked North a week later, NAIT didn't have clue what was going on, so they blamed farmers.

Oh my gosh really since 2009? Where do the years go eh. Yes Nait is pretty shit. The tags seem to not read regularly, the records dont seem to transfer just as regularly. I phoned up Nait a couple of weeks ago to ask them to change my listings to beef rather than dairy. So I dont pay the $13 dairy kill fee. Hmm I see a couple still went through as dairy in the last kill. Seems they cant get that right either.

No Aj, it can't be stink bugs in those traps - according to MPI they aren't in NZ ;-) That is a serious concern and it is interesting that MPI is still maintaining they aren't here when they are being caught in traps.

They keep catching individuals, not a breeding colony.

Donker - I hear what you say about burnout - down our way I hear a lot of it is due to false callouts e.g. members of the public not understanding farming. There are animal welfare 'flying squads' consisting of Vets,Dairy processor rep, DairyNZ staff, etc down our way who will visit a farm if it is called in to them by people in the community. Many of the callouts are often found to be where there are mental health issues (stress) with the farmer. I would expect these 'squads' to be operating throughout other areas of the country.

Nait is only as good as the people entering the data. Here is the guts of a conversation I had with a large stock firm, that sold my cows for me . "Hi you sold some cows for me at so and so stockyard , the movement hasn't been recorded. No, I don't remember that so we can't of. "Um. you've sent me a cheque for them, so you must have a record of it . "nope , never heard of you or your cows . Hmmm, ok , do you want me to ring Nait , and get them to sort it out?. "If you want."
Nait sorted it out with one phone call.

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