Several cases of bovine anaemia have been reported on the north coast caused by the Theileria orientalis group, that have caused death in calves in the region.
Theileria are protozoan parasites that can be carried by bush ticks and affected calves are typically in the 2–3 month age bracket (although older calves have also been diagnosed with the disease), and, are found to be suddenly lethargic and down. Some farmers have reported finding the best calf in the paddock unexpectedly dead.
The blood parasite is transmitted via the bush tick (Haemophysalis) and the clinical signs in affected calves can be attributed to an anaemia caused by the destruction and removal of red blood cells from circulation.
Liz Bolin, District Veterinarian said, ‘Current treatment options for cattle that are affected with Theileria are limited and responses to treatment are often poor especially in severely affected animals.’
‘There is currently no vaccine available for Theileria and treatment with antimicrobials has produced variable results.’
On clinical exam calves will often be in good body condition, with or without a fever and either pale or yellow gums. The most striking feature seen at necropsy is an enlarged ochre coloured liver.
‘Tick control won’t prevent transmission of the disease however studies have shown that treatment of cattle for ticks has been linked to lower detections of the blood parasite,’ said Ms Bolin.
Stress minimisation is also an important aspect of managing affected cattle as the stress associated with mustering and yarding can frequently lead to death.
For more advice please contact your private veterinarian or the North Coast Local Land Services District Veterinarian team.
