Tuesday, 21 November 2017 13:55

One more positive M.Bovis result

Written by  Nigel Malthus
Geoff Gwyn. Geoff Gwyn.

One of the two new South Canterbury dairy farms placed under restrictions recently has tested positive for Mycoplasma bovis infection.

The Ministry for Primary Industries says testing is ongoing on the second property in Waimate, which is under precautionary restrictions due to its association with the new infected farm.

In addition to these two farms, MPI has placed another farm in the area under the same controls while further testing is underway to determine if it too is infected.

MPI’s incident controller of the Mycoplasma bovis response, David Yard, says all three farms are in the same district and a couple of them neighbour Van Leeuwen Dairy Group properties.

“All these farms are under Restricted Place Notices, controlling the movement of animals and other risk goods on and off the farms.

“We still have a lot of work to do ascertaining the source of infection at the confirmed infected property and building a picture of animal movements between all three farms and possible other farms.”

All three farms were identified through the ministry’s comprehensive surveillance and tracing programme, which has now tested at least 40,000 samples of milk, blood and swabs.

MPI director of response Geoff Gwyn says despite the latest development it is still hoping to contain and eradicate the disease.

“This is exactly why we are doing this testing work – to know where the disease is in order to contain and remove it,” Gwyn says.

“We do not believe the new suspect properties represent a game-changer. These farms are in the same area as all the known-infected properties and neighbouring Van Leeuwen Dairy Group farms.

“Our investigators are still building a picture of how animals on the farms could have been infected, if indeed they are, and what stock movements may have taken place onto the farms.”

Mycoplasma bovis is spread during close and prolonged contact between animals and by direct movement of stock.

“The discovery of the new potentially positive properties has not changed our position on this. We do not believe there is a significant risk of disease spread across fences,” Gwyn says.

So far only seven farms are confirmed with the disease, five of them part of the Van Leeuwen Dairy Group, where the disease was discovered in July for the first time in New Zealand. However, the new development brings to 22 the number of properties under Restricted Place Notices.

Last month MPI announced a decision to cull all cows from infected farms – about 4000 animals. It says the cull is “progressing steadily and to plan.”

Meanwhile, the total number of samples required is being revised upward, largely because MPI has decided to test more low-risk properties than first estimated.

Gwyn says MPI is still working to find the source of the outbreak, across six broad possibilities – germ plasm (semen and embryos), feed, live animals, biologicals (veterinary medicine), fomites (machinery and equipment surfaces) or other animals.

The strain is also being genotyped to help identify the likely overseas origin, expected to be known by the end of November.

“My position would be that the public of NZ want us as much as possible to eradicate this disease. And just because we can’t specifically identify an entry pathway I don’t think that would change.”

Gywn says if M.bovis was found to be endemic there would be no point in culling stock, but instead management.

“But we’re not in that space. We’re quite confident it is localised.”

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