Theileriosis

What to look for

Usually seen recently after cattle have been introduced to a herd.

• Abortions in late pregnancy or stillborn calves
• Anaemia and jaundice (pale or yellowish mucous membranes)
• Cattle get out of breath easily when moved
• Production losses
• Poor appetite, weakness and depression
• Occasional deaths

Cause - a blood parasite (Theileria)

This parasite is transmitted by bush ticks (Haemaphysalis) but may also spread by multiple use of vaccination guns, ear taggers or other husbandry devices that are contaminated with blood. Theileria is widespread in Queensland and Northern NSW and has been found in all states except South Australia and Tasmania. In herds where the parasite is established there is usually little evidence of disease unless animals are introduced that have not previously encountered the parasite. Once animals are infected they are likely to remain infected for life.

Animals likely to be affected

Cows in late pregnancy or early lactation. Outbreaks usually follow the recent introduction of new animals to the herd.

Other diseases with similar signs

Other causes of anaemia include Brassica poisoning (kale anaemia); Pimelia poisoning (St George disease); bacillary haemoglobinuria; leptospirosis in calves; post-parturient haemoglobinuria (hypophosphataemia); chronic copper poisoning and snake bite. In tropical and subtropical areas, tick fever and anaplasmosis should be excluded.

Confirming the diagnosis

Laboratory tests can confirm the presence of a specific type of anaemia and can demonstrate the causative parasite in blood smears.

Prevention

Prevention of Theileria is difficult once it is established in the local bush tick population. However you can reduce the risk of introducing this parasite to your farm by good biosecurity measures. Infected animals may not show any signs of disease so it pays to seek veterinary advice if planning cattle movements to or from areas where the disease occurs. Avoid introducing infected animals into if your herd is free of the infection, especially if cows are in late pregnancy.

Risk factors

• Introducing pregnant animals that are free of Theileria to an infected herd
• Introducing infected animals into herds that are free of the infection

Treatment

No specific treatment is available, so good nutrition and nursing care is the best option.

Do you want animal health info delivered?

Subscribe to Dairy Australia publications