Understanding Tick Outbreak in New Zealand Part One: What Are the Risks?

New Zealand beef and dairy farmers are getting to grips with a strain of Theilera orientalis, a parasite that can cause high fever and pluroplasmosis.
calendar icon 5 November 2013
clock icon 4 minute read

The advice from Dairy New Zealand is to keep eyes peeled for cattle straggling when walking and for animals with pale vulvas. Suspected animals should be rested and given high quality food and water

Cases of cattle being affected by the blood-borne parasite Theileria orientalis, which causes anaemia, have been on the increase since late 2012, particularly in the northern half of the North Island, write health advisers at Dairy New Zealand. 

Photo Courtesy of Dairy New Zealand

This is due to a likely increase in the number of ticks this season, which carry Theileria, and a new strain of the parasite called Ikeda.

So far, Theileria has only affected a very small proportion of New Zealand dairy herds, mainly in the North Island - around Waikato, King Country and the Bay of Plenty. Cases have also been confirmed in Whanganui, Taranaki, Reporoa and Rangiora.

If animals are stressed or left untreated, Theileria can lead to death in cattle as their blood can’t carry enough oxygen around the body.

Cows during calving have a changing requirement for energy as they transition to milking, and this along with changes to the immune system makes them more susceptible to the infection. Young calves (2-3 months) and recently calved cows are also more susceptible.

Slowing the spread

Theileria infection is caused by a parasite transmitted by ticks when they feed on the animal’s blood – it is not passed on by cow-to-cow contact. Cattle are at risk of infection when moved to areas where ticks are present. Likewise, if infected cattle are transported, they can spread infection to ticks in the new location.

Numbers of reported cases are still low and, at an individual herd level, impacts from Theileria are likely to reduce over time as cattle build up immunity to the new strain.


  • Regularly check all classes of stock for ticks. Look for them around the tail head, base of udder and inside the legs.
  • Apply a tick control product specifically for cattle, following the advice of your veterinarian and/or product instructions. Talk to your veterinarian for options.
  • Quarantine new stock coming on to your farm for seven days and treat them for ticks

Signs of Anaemia

  •  Cows straggling on the walk to the shed.
  •  Increased respiratory and heart rate.
  •  Pale, rather than healthy pink, vulva.
  •  Pale udder, yellow eyes.
  •  Cows have no strength or energy to do anything.

Treating Affected Cattle

  • Minimise stress and movement of affected animals.
  • Give affected animals easy to eat, high quality feed and plenty of water.
  • Handle the affected cattle only when necessary.
  • Treatments are available. Contact your veterinarian for advice.

Five key factors for assessing the risk of Theileria infection in your herd

1.Is Theileria in your area?

Northland, Waikato, Bay of Plenty, King Country, Taranaki, Whanganui and Wairarapa (and one case in Rangiora) are all regions with confirmed cases. However, Theileria could be more widespread as signs can be missed or not show up in affected cattle.

2. Are there ticks present? 

All cattle in areas where ticks are present are considered at risk of being infected, particularly the North Island. However, having ticks does not necessarily mean your herd is infected. Ticks are small and difficult to see, and very few are needed to transmit Theileria. The disease can also be
spread by tick larvae, nymphs or adults on other animals such as birds, rabbits and deer.

3. Has there been cattle movement on-off your farm?

Have cattle from Theileria-infected areas been introduced to your farm, or brought back from off-farm grazing, or new cattle or service bulls brought in from infected areas? Cattle that may not have been exposed to Theileria being moved to a place where Theileria are present also increases your risk.

4. Are young stock at risk of infection?

Young calves up to about six or seven months of age are susceptible. Their immune systems are still developing and they are also coping with changes such as weaning and being transported to other farms.

5. Are cattle undergoing changes like calving or are they sick?

Cattle in late pregnancy, calving and early lactation, calves being weaned and potentially service bulls when they begin mating, are more at risk. Sick and poor condition cattle are also more susceptible to infection

For Further advice - consult you veterinarian or click here


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