Theileria 

Has your farm been impacted by the Theileria outbreaks?

The impact of Bovine anaemia caused by Theileria orientalis can vary from subtle decreases in production, to severe and economically crippling. Many farms may have the disease in their herds without knowing it. One or two deaths, or a drop in milk production in some cows may be all that is seen. These events may be put down to other diseases. Veterinarians are reporting that the disease is now being seen over large geographical areas throughout Gippsland in beef and dairy cattle. It is estimated that over 200 deaths have been linked to the parasite in East Gippsland alone since first seen in 2009, and these are the ones veterinarians have responded to. 

So what is Theileria?

Theileria is a blood parasite that is transmitted by ticks. As ticks feed on cattle, Theileria is injected into the cow’s bloodstream through the tick’s saliva. The parasite enters red blood cells which destroys the cell. This leads to anaemia, and effects the amount of oxygen carrying capacity of the cow. It is thought that the bush tick (Haemaphysalis longicornis) is responsible for its spread. The time that the ticks actually spend on cattle is very short, with most of the life cycle of the tick being in the pasture, and it’s because of this that ticks may not been seen on cattle where an outbreak is occurring. 

What are the signs to look out for?

  • Decreased milk production
  • Lack of appetite and weight loss
  • Lethargy
  • Fever
  • Exercise intolerance (lag behind the mob)
  • Pale and/or yellow gums and mucous membrane colour
  • Staggering
  • Gasping for breath or increased respiratory rate
  • Abortions
  • Jugular pulsation
  • Downer cow
  • Eating dirt
  • Deaths 

What farmers can do

The clinical signs listed above are not specific for Theileria, and can be seen with many other medical conditions, especially around calving time. If you have cattle that you suspect have Theileria, contact your local vet. A good physical exam and a simple blood test will confirm the diagnosis.

Risk of Theileria might also be minimised through the following:

  • Avoid importing animals from known affected properties
  • Rotational grazing may control ticks (eradication of ticks very difficult)
  • High quality feed and rest of suspect cases
  • Keep a close eye on calves when they are 6-12 weeks if adult cows have been affected
  • Keep an eye on introduced cattle after 3-8 weeks
  • Wash castration knives, and avoid using the same needle on more than one animal

Currently no medications are registered in Australia for the treatment of cattle with Theileria. Good nursing care of affected stock, and minimising stress and movement are the most important in the recovery of stock. Antibiotics and anti-inflammatories may assist in some cases but in severe cases the cow should be humanely euthanised. 

What research is being done?

Gippsland is leading the way in research to this poorly understood disease. Private veterinary practitioners in conjunction with DEPI and Melbourne university are involved in a prevalence study in farms where clinical cases have been seen. Other Gippsland studies have examined the effects of the parasite on production. In addition, a large study is now underway into the transmission of Theileria in Victoria. This will look into whether other ticks apart from the bush tick is involved in the transmission. It will also look into the role biting flies and mosquitoes have in the spread of the disease. Husbandry practices including ear notching, castrations, and multiple use of a single needle between cows will also be examined for risk. This research is being assisted by Meat and Livestock Australia, The University of Sydney, DEPI, United Dairyfarmers of Victoria, and Main Street Veterinary Clinic Bairnsdale. Further funding is being sort from other industry and government organisations. Farmers can assist with this study by collecting any ticks that they find on cattle and dropping them off at their local vets.

 

Further information of Theileria can be requested from your vet.