The first major outbreak of theileria – a mainly tick spread disease occasionally fatal to cattle – in the South Island has been found in a dairy herd on the West Coast.
Tests confirmed last week that the unidentified herd had theileria after a farmer reported cows were showing signs of anaemia. Cows within the herd were understood to have previously been grazed in Canterbury.
First appearing in Northland in 2012, the theileria strain called ikeda, a blood-borne parasite, was across much of the North Island.
Known cases were previously restricted in the south to a single dairy cow last year in Canterbury, believed to have been moved from the North Island, and possibly infected heifers more lately coming from the Hawke s Bay.
The Ministry of Primary Industries is understood to be sending out information to veterinarians to restrict its spread and raise awareness of the disease and animal management.
A local population of ticks either in Canterbury or the West Coast is suspected to be responsible for the infection as there was no apparent North Island connection.
This has yet to be confirmed as an investigation failed to fully show that ikeda was spread by a tick to infect the Canterbury dairy cow previously.
However, authorities believe the outbreak shows it will reach more South Island farms in the future. This depends on how easily ticks establish south of the Tasman area where they are found. While ticks have established for short periods in southern parts of the South Island previously, the climate is often unsuitable for numbers building.
The disease causes anaemia in cows in a breakdown of red cells. Signs include red urine, low appetite, pale mucous membranes, lethargy, and low milk production.
DairyNZ says farmers need to be aware of the disease and its symptoms and regional teams will work with them to give advice.
DairyNZ veterinary technical policy adviser Nita Harding said theileria had spread widely in the north.
“Theileria is only in areas where there are ticks so we have been keeping a close eye on the South Island because we know there are ticks in the Nelson and Marlborough area. We are not aware of ticks elsewhere, but that’s not to say there could be small populations that we aren’t aware of and this (West Coast) case only came to light the last few weeks.”
She said further investigations would hopefully shed light if the theileria infection had come from Canterbury or the West Coast.
Southern farmers observing anaemia in cows should contact their vets, she said.
Theileria cases jumped by 45 in the month after July 11 to bring the total to 717 mostly in dairy herds. Most cases this year had been concentrated around the Waikato and Auckland regions with drift towards the East Cape, Manawatu and Taranaki.