Bovine anaemia: Theileria is more than a bug in the blood

Theileriosis in Australia is caused by the blood parasite Theileria orientalis. T. orientalis variant Buffeli has been present for more than 100 years. The disease has historically been benign, causing only mild anaemia in cattle. Infections have only rarely been severe enough to cause significant morbidity or mortality. This, however, is changing and producers need to be aware of the emerging threat.

The parasite is now endemic in many coastal regions of New South Wales, Victoria and Queensland and has been detected in all states and territories except Tasmania. Until recently, only two sub-clinical cases had been recorded in Western Australia and the first outbreak in South Australia was recorded in October 2014.

The bugs are changing

Since late 2005, there has been a significant increase in both the number and severity of clinical Theileria infections in cattle in eastern Australia. These cases have been reported in areas where the disease had previously not been noted and have often been associated with the introduction of animals from known endemic areas. In some cases, the disease has resulted in mortality rates of up to 30%.

Genetic typing of the Theileria organisms in these cases revealed the presence of strains previously undetected in Australia – T. orientalis var. Ikeda and T. orientalis var. Chitose.

Further research has shown that the ikeda variant is present in all cases of clinical disease. The new disease syndrome is known as ‘bovine anemia due to T. orientalis group’, or BATOG. Although clunky, this name was specifically chosen to distinguish the condition from the highly pathogenic East Coast Fever, which is also caused by Theileria, but is confined to eastern Africa.

Signs of BATOG

BATOG is associated with the destruction of red blood cells. Young cattle (2–3 months old), late-pregnancy and recently calved cows are most likely to be affected by BATOG.

More common signs, particularly in late pregnancy or early lactation, include:

• anemia and pallor
• fever
• weakness
• red urine
• jaundice
• death
• late-stage abortions
• premature births

Other signs include:

• listlessness
• lack of appetite, weight loss
• wobbly gait
• laboured breathing

Getting around

The Theileria parasite has been shown to be carried by the bush tick (Haemaphysalis longicornis). Current evidence indicates that less than ten ticks are required to transfer a sufficient number of Theileria parasites to cause BATOG.

Avoiding theileriosis

While theileriosis is not a notifiable disease, some affected herds have experienced significant production losses. Last year, several MBfP BetterBeef Network groups in Victoria discussed prevention strategies that could be applied in southern beef production systems. These include:

Review on-farm biosecurity strategies

• quarantine new stock and consider treating with a chemical registered for the control of ticks on cattle. Check with the vendor/agent if new stock have come from a herd/area known to have theileriosis
• check for the presence of ticks

Revise existing health management plan

• regularly monitor stock for tick infestations
• maintain stock in the best condition possible to promote resilience

Nutritional management

• maintain quality feed supply to enable animals to be in the best condition to tolerate possible infections
• speak with a veterinarian about iron supplements in the event of an outbreak

Drenching and vaccination practices

• treat stock for tick infestations when detected
• maintain routine vaccinations to ensure good immunity against other diseases

Further information

• Greg Ferrier, VIC DPI Beef Industry Development Officer T: 02 6030 4609
• Benign theileriosis
• Victorian Department of Environment and Primary Industries
• Western Australian Department of Agriculture and Food
• NSW Department of Primary Industries