'Mycoplasma bovis' cases still rising in South Island

Connections have been found between cows infected by mycoplasma bovis at different sites.

The number of New Zealand farms infected with Mycoplasma bovis continues to rise, but the latest cases are connected to previously known ones.

On April 24, the Ministry for Primary Industries sent out its 74th update since the outbreak began last July.

Thirty-seven farms have been confirmed with the bacterial cattle disease. However, the "current" number stands at 32, because cattle have been culled on some farms and the properties are being disinfected.

A Hawke's Bay farm, the only North Island location, is still listed as infected.

In the South Island, 10 of the 13 Southland farms are still infected, as are 10 of the 11 in North Otago-South Canterbury, the two in Middlemarch, all seven in Mid-Canterbury and two of the three elsewhere in Canterbury.

Fifty-two properties are under movement restrictions.

The ministry said such restrictions were imposed when it had reason to be concerned about potential infection.

"This is different to MPI identifying a property for surveillance, which simply means there's testing to be completed," the update said.

"That testing could be recommended due to the property's geographic location, the movements of cattle on and off the farm, or some other risk factors.

"Rest assured, where there is considered to be any significant risk, a farm is under quarantine.

"Farm operations on farms under surveillance should continue as normal during the period of testing, unless farmers have been informed otherwise by MPI."

The ministry is looking into developing a test for Mycoplasma bovis. It is working with commercial laboratories and industry representatives on a commercial diagnostic tool so farmers can test their own stock.

The ministry said the tool would be released once sampling guidelines, a testing strategy and possibly accreditation were in place to ensure it could be applied and interpreted accurately.

"We have identified that interpreting a one-off test result, even at the herd level, in isolation to other factors, is challenging and carries inherent risk for farmers," ministry response director Geoff Gwyn said.

"The tests currently available will lead to a significant number of farms being falsely identified as positive and farms that may be real positives being missed.

"That's why we are developing robust processes, including a testing strategy and sampling guidelines which may form part of an accreditation programme," he said.

The latter would consider factors such as herd management, animal health and record-keeping as well as test results, all of which would inform farmers of the likely risk of the disease in their herd.

Ministry response liaison officer Elizabeth Taylor told Central Rural Life the test, once verified, would be priced for commercial use.

The ministry was unlikely to be involved in that aspect, "as it will be privatised and rolled out on the market".

"We cannot give a time scale, unfortunately," she said.

The ministry had nearly finished testing milk from every dairy farm in New Zealand, Mr Gwyn said.

"We acknowledge that some farmers may be disappointed they don't have access to a commercial diagnostic tool now to give them some certainty about whether their animals, or animals they may be purchasing, carry the infection.

"However, it's critically important that we don't rush this — we have to get it right."

sally.brooker@alliedpress.co.nz

Central Rural Life