with Phil Rennie
There continue to be new cases of Theileriosis on farms in the upper North Island. Most are either young calves or previously-unaffected adult cows with a history of grazing off-farm where infected tick populations are high. The disease typically manifests itself at times of high stress, such as early lactation when the cows are transitioning into peak milk production.
The disease is caused by the parasite Theileria orientalis and is spread by infected ticks when they feed on animals’ blood.
The disease affects both beef and dairy cattle and it can infect cattle of any age. Cows during the calving period and potentially young cattle – aged two-three months – are most at risk of disease. Fortunately, 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 via infected ticks on animals (including all wildlife) or Theileria-infected cattle, which then infect the local resident tick population.
Signs of disease associated with anaemia include the following: Cows are lethargic and lag behind the main mob. Cows which don’t respond as expected to treatment for conditions such as milk fever. Cows off their food and appear hollow-sided in the abdomen. Pale or yellow vulval mucous membranes and/or whites of eyes. 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. For example, gastrointestinal parasites, BVD virus, facial eczema challenge, trace element deficiencies.
Control of ticks is strongly advised – particularly if moving cattle from one property to another. This applies especially if moving from a more Northern property or there is a known history of ticks with signs associated with anaemia in the past. This can be achieved by treating all cattle with products containing the active ingredient flumethrin before leaving the property or on arrival before mixing with other cattle.
If cows or heifers are being grazed off-farm onto a property with a history of Theileria and/or a high tick population, treatment is ideally applied five days before cattle are moved and repeated as often as every three weeks while away grazing to reduce risk of infection or bringing the disease back to the home property.
Where possible ensure all underlying causes of stress or concurrent disease are being controlled. For example, efficient transition and nutritional management, effective parasite control, effective trace element supplementation, monitoring and control of BVD, and facial eczema prevention.
Successful treatment of cattle infected with Theileria depends on the incidence and severity.
Feel free to contact your local vet clinic for further information and/or advice if you have any concerns about your cattle.