Spring M bovis spike predicted
A spike in the number of dairy herds testing positive in spring for Mycoplasma bovis is predicted by a panel of experts appointed by the Ministry for Primary Industries. This was because dairy replacement stock, largely 2016 and 2017-born heifers, were the group most likely to be infected, but undetected. As 2016-born heifers calve for the first time and go into the milking herd, they will then be tested for the disease as part of national bulk milk testing. ‘‘There is an expectation that some new herds will test positive this spring. We don’t know how many. Hopefully, not too many,’’ says the chairman of MPI’S Mycoplasma bovis technical advisory group (TAG) Scott Mcdougall. ‘‘Because of the number of animal movements and calves that may have moved off infected farms and not been recorded, there could be potentially some pockets of the disease out there we don’t know about yet.’’ In a phased eradication costing $886 million, the Government will cull about 150,000 cattle in an attempt to rid the country of the Mycoplasma bovis, a bacterial disease which can cause untreatable mastitis, abortion and arthritis in cows. The disease is harmless to humans and is not transmitted through meat or milk. An MPI spokesperson said that while the aim was to eradicate the disease, triggers may cause this to be revisited by MPI and its industry partners in the eradication programme. Factors that could prompt such a re-evaluation included the results of the spring round of bulk milk testing (which would not be available until late in the year), the detection of a different genetic strain of the disease, or the discovery of another significant cluster of affected farms outside the current known network connected through animal movements. Mcdougall said that while the group of technical experts only narrowly voted six-to-four in favour of phased eradication ‘‘it wasn’t that black and white. ‘‘There was a range of opinions in the group and a range of experiences.’’ Some said getting rid of the disease was no longer achievable or economically rational. Uncertainty was not about whether eradication was technically achievable, but because of the number of potential animal movements. ‘‘Their argument was that maybe the problem is bigger than we know about.’’ They were also worried about the effect killing entire herds was having on the wellbeing of farmers. However, there had already been three rounds of milking testing of the national dairy herd and no positive test results outside of herds linked by animal movements. When cows were stressed, such as during calving in spring, they were more likely to show signs of the disease and shed the M bovis bacteria. While the number of infected beef herds was probably low, there was some uncertainty about this. Farmers were now much more careful about farm biosecurity, buying stock and waste milk. ‘‘The risk of M bovis spreading now is much less than a year or two ago.’’ Eradication was a big call, but a decision to manage the disease meant it would spread around New Zealand. ‘‘We couldn’t turn around in a year or two and change our mind and try and eradicate it. It’s a one-off opportunity,’’ said Mcdougall.