A change in the severity of the disease theileriosis in NSW cattle is being investigated by veterinarians from NSW Department of Primary Industries (DPI) and the Livestock Health and Pest Authority.

“Theileriosis is a disease affecting red blood cells that has been present in NSW cattle for 50 years – but in the last year it has emerged as a serious cattle health problem in parts of the State,” said NSW DPI regional veterinary officer Paul Freeman.

“In a recent case on the Mid North Coast, multiple deaths and abortions were seen in introduced cattle on a beef cattle property at Dorrigo.”

Theileriosis is caused by a parasite of red blood cells spread by bush ticks – but not by either cattle tick or paralysis ticks.

Theileria are normally common at low numbers in blood smears from healthy animals.

Mr Freeman said in the past, severe illness due to theileriosis was rare and associated with very high levels of blood cell parasitism and most affected animals recovered uneventfully.

“In the last year, however, there has been a five-fold increase in the number of reported outbreaks of clinical theileriosis in cattle on previous years,” he said.

“The first cases were seen in the Gloucester-Kempsey area and the eastern fall country around Walcha.

“Since then cases have been noted from most coastal areas of NSW and the Northern Table-lands.”

Mr Freeman said the majority of the recent theileriosis outbreaks had been in cattle recently introduced from areas free of bush ticks.

“Unlike the sporadic cases seen in the past, these outbreaks featured severe symptoms and many deaths in cattle of all ages,” he said.

Clinical signs in affected animals include anaemia, lethargy, poor milk production and sometimes jaundice.

Abortion is a frequent outcome in pregnant animals.

Mr Freeman said the change in the severity of the disease in NSW may be due to a slight variation in the theileriosis strain – but this is not yet clear.

“NSW DPI has arranged for isolates from NSW strains of theileria to go for DNA analysis,” he said.

“This will help us understand the difference in severity of Theileria within NSW and Queensland.

“Different transmission rates by tick vectors is another possible cause of variation in the disease’s severity.”

Mr Freeman said a workshop on theileriosis is being held at the LHPA District Veterinarians’ conference at Port Macquarie this week, to develop a greater understanding about these issues.

This will be attended by experts in the field of tick transmissible diseases including Professor Sugimoto from Japan, who is keen to increase the understanding of the epidemiology of theileriosis infection in Australia.

Mr Freeman said that there was no recommended treatment for theileriosis in Australia.

“However, in other countries drugs that are effective against other species of theileria are used in the treatment of clinical cases,” he said.

“Contact has been made with animal health companies regarding the potential to trial treatment options for the disease.”

NSW DPI is also advising cattle producers on the NSW Mid North Coast to maintain good bush tick control, particularly on introduced cattle – to reduce the likelihood of cattle getting the disease.

Contact the district veterinarian with your local Livestock Health and Pest Authority.

Further reading

Cattle health and disease