Tick tock race against infection

Dairy farmers are being urged to check their cows for ticks.

DairyNZ is alerting all farmers (including graziers) to keep an eye out for signs of a tick-carried disease that causes anaemia in cattle and to actively manage the risks of ticks to their herds.

Theileriosis is a disease caused by a species of theileria, a blood-borne parasite that affects only cattle and is primarily transmitted by ticks. A new strain of Theileria orientalis called ikeda was first identified in Northland in late 2012. This strain has been associated with anaemia and death in cattle.

DairyNZ's warning comes after the Ministry for Primary Industries (MPI) confirmed that a case of theileriosis hit a South Island West Coast farm this spring. The MPI says a population of infected ticks in Canterbury or the West Coast was responsible for transmitting infection to the 188-cow dairy herd.

DairyNZ technical veterinary adviser Dr Nita Harding says cattle are at risk when moved to areas where infected ticks are present. Likewise, if an infected animal is transported it can spread infection to ticks in the new location, in turn spreading disease to uninfected animals.

"We are concerned that there may be infected tick populations in the South Island now. This latest case was linked to cows being grazed in the Canterbury area and then being brought back to the West Coast," says Dr Harding. "It's important that farmers remain vigilant and monitor stock, particularly weaned calves."

"Cases of theileriosis are usually higher in autumn and spring. However, at any time of year, if animals present with signs of anaemia, a veterinarian should be consulted.

"We are advising farmers to consider the risk of moving young stock to grazier or run-off properties where the level of tick activity and theileria may be greater than on the home property. Stock should be regularly checked for signs of anaemia. Tick treatments may be helpful for reducing the tick load and severity of infection and farmers should seek vet advice regarding the most appropriate treatment for their animals.

"This is a disease that can result in serious illness and death of cattle and has affected some herds quite badly."

Dr Harding says more South Island cases are likely now that the disease has been diagnosed there, especially in Nelson/Marlborough, where ticks are known to be present.

"At this stage, we just don't know exactly the degree of infestation or location of local tick populations and therefore the level of risk to different regions in the South Island," she says.

Dr Harding says theileria is now widespread over the northern half of the North Island with cases diagnosed across Northland, Waikato, Bay of Plenty, Taranaki, the King Country, Whanganui and Hawke's Bay. Cases have also been reported from the lower half of the North Island. The MPI has reported around 116 new cases since September.

For advice on managing theileria see www.dairynz.co.nz/theileria