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In New Zealand, the main vector of the blood parasite Theileria is the cattle tick, although biting flies and sucking lice can be involved.

Until recently, Theileriosis was a sporadic event that only affected cattle debilitated by another disease. T. orientalis was first identified in New Zealand in 1982 in a dairy farm near Wellsford. From 2000 to August 2012, there were only 12 notifications of the disease to the Ministry usually involving only one animal. Since late August 2012, there have been more than 200 notifications of Theileria associated anaemia, and the mortality and morbidity rates experienced by many of the affected herds have been far greater than ever before.

A previously unrecorded strain of Theileria (ikeda) is associated with these outbreaks.

When are signs of Theileriosis most likely to be seen?

  • Around calving time

  • Calves from weaning up to 6-7 months of age

  • Sick animals or animals recovering from sickness

  • Mating time

What signs can be seen in cows infected with Theileria?

  • Cows getting behind on the way to the shed

  • Fast breathing

  • Pale or sometimes yellow mucosa of the vulva lips

  • Whites of the eye yellow

  • Sick cows do not respond to treatment as to be expected

  • Excessive weight loss in adult animals or poor growth in young animals

  • Decrease milk production

  • Pale udder

How to treat affected animals?

  • Minimise stress and movement

  • Put affected milking cows on once-a-day and keep them as close to the shed as possible

  • Provide high quality feed and ad-lib access to fresh water

  • Treatments are available, contact us for advice

How to assess the risk of theileriosis in your herd?

  • Are there ticks present?

  • Has there been movement of cattle from infected areas?
    New cattle, breeding bulls, young stock returned from grazing.

  • Are cattle under significant stress?
    Cows during late pregnancy, calving and early lactation.
    Calves being weaned.

  • Ill thrifty cattle are more at risk

How to minimize the effects of potential infection?

  • Talk to your vet about the risks in your herd and area and ways of prevention.

  • Monitor the overall health and condition of your cattle closely.

  • Inspect cattle for the presence of ticks. Use Tick treatmentsto reduce tick burden. Ideally, tick treatments should be given at least twice, three-to-four weeks apart,with the first treatment given three weeks before calving.

  • Determine health status of bought in stock. Ask for records of veterinary treatments.

  • Quarantine new stock for at least 7 days. Inspect for ticks thoroughly during this period, treat when needed.


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