There have been many new cases of Theileria on farms in Manawatu this season.

Most of the affected cows had a history of grazing off-farm over the winter (i.e. often outside of the region where infected tick populations are high), and typically the disease manifested in early lactation when the cows were back home.

Theileria orientalis is spread by infected ticks when they feed on the animals’ blood.

The disease affects both beef and dairy cattle and it can infect cattle of any age. Cows over the calving period and potentially young cattle (two to three months of age) are most at risk of disease. There are no human health risks associated with this disease.

Most cattle will show no obvious signs of disease but some cattle within the herd with Theileria can progress to severe anaemia and potentially death if left untreated.

Theileria can enter a property either via infected ticks on animals (including all wildlife) or via Theileria-infected cattle which then infect the local resident tick population.

The disease causes signs associated with anaemia:

  • Pale or yellow vulval mucous membranes.
  • Whites of eyes are pale to yellow (blood vessels are not clearly visible).
  • Cows stay or lag behind the main mob, i.e. they are lethargic.
  • Cows do not respond as expected to treatment for conditions such as milk fever.
  • Cows are off their food and appear hollow-sided in the abdomen.
  • There is a decrease in milk production, and a potential for poor reproductive performance.
  • There may be poor health and low performance in your young stock.
  • There may be deaths especially close to calving or early lactation.

Disease outbreaks can be triggered by stress, particularly around calving time, or even when there is underlying disease and/or certain nutritional deficiencies, e.g. gut parasites, BVD, facial eczema, trace element deficiency.

Control of ticks is strongly advised particularly if moving cattle from one property to another (and especially if there is a known history of ticks) or if there have been signs associated with anaemia in the past. This can be achieved by treating all cattle with Flumethrin (e.g. Bayticol/Bantix) before leaving the property.

If cows or heifers are being grazed off-farm onto a property with a history of Theileria and/or a high tick population, Bayticol/Bantix should be applied five days before the cattle are moved and repeated every three weeks while away grazing to reduce the risk of infection.

Lastly, ensure that all underlying causes of stress or concurrent disease are being controlled, e.g. efficient transition and nutritional management, effective parasite control, effective trace element supplementation, monitoring and control of BVD and facial eczema prevention.

Treatment of infected cattle with symptoms of Theileria depends on the incidence and severity.

Please do not hesitate to contact your veterinarian for further information and/or advice if you have any concerns.


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