Information on Benign Theileriosis
Update 29 May 2012
About benign theileriosis
Benign theileriosis is a tick-borne disease caused by intracellular blood parasites belonging to the Theileria orientalis group. This disease represents no threat to human health.
Reports of cattle that have contracted the disease were received in 2011 from producers in north east Victoria indicating an upsurge in cases. Wet conditions are likely to have stimulated increased tick activity and this may have lead to increased instances of benign theileriosis. It is also possible that infected ticks have been inadvertently transported to north east Victoria from other areas.
Cases reached a peak of approximately 15 reports per month at the end of 2011 and have dropped to around five reports per month in early 2012.
The disease seen in Australia is usually mild or 'benign' – deaths are uncommon in areas where the disease is endemic. The disease can however be more severe when it moves into new areas, where animals have not been previously exposed.
Where has it occurred?
The location of clinical cases of benign theileriosis reported to the Department of Primary Industries (DPI) since 1 January 2010 is shown in Figure 1. During May 2012, the first case, outside Gippsland and northern/north eastern Victoria, was reported in the south west of the state.
The shires in which the clinical cases shown in Figure 1 have been reported from are:
- Alpine Shire
- Bass Coast Shire
- Baw Baw Shire
- Campaspe Shire
- Corangamite Shire
- Cardinia Shire
- East Gippsland Shire
- Indigo Shire
- Mitchell Shire
- Moira Shire
- South Gippsland Shire
- Strathbogie Shire
- Towong Shire
- Wellington Shire
- Wodonga Shire
What can producers do?
Concerned producers must contact their veterinarians about prevention and possible treatments.
Following simple biosecurity procedures is the best action producers can take to help prevent the spread of the disease. Here are some specific preventative steps for producers:
- When buying in new stock, ascertain their health status. Avoid importing animals from known affected properties or localities.
- Where the health status of bought-in stock is unknown, treatment with a registered tick treatment may be advisable prior to introduction. When using insecticides, always consult with your veterinarian and remember to observe the prescribed withholding periods before marketing products of treated animals.
- Rotational grazing practices may also help control ticks; the use of non-bovine species may act as 'vacuum cleaners' to remove ticks from pasture before the introduction of cattle.
- Cattle showing clinical benign theileriois must not be stressed. They should be rested, nursed and given high quality feed.
- Seek veterinary advice if cattle are showing signs of fever, anaemia, multiple abortions or any other unusual signs.
Bush ticks (Haemaphysalis longicornis) are mainly a cattle parasite, but are able to attach to other mammals including wildlife, birds, livestock (including horses, sheep, goats and poultry) and domestic animals such as dogs and cats. In sheep, bush ticks prefer to attach mainly on body parts not covered by wool.
The most common sites of attachment on cattle are around the tail, on the udder, inside the legs, on the brisket, in the ears, and occasionally on the face and neck.
Although it may cause tick irritation and local reactions in all species, H. longicornis only transmits benign theileriosis to cattle.
Treatment options for benign theileriosis are limited to supportive care and symptomatic treatment.
There is currently no drug registered in Australia for the treatment of benign theileriosis. Some veterinarians have reported variable responses to treatment with certain antibiotics and antiprotozoals, but there are residue risks and these drugs should be used only under veterinary supervision.
Blood transfusion has been performed occasionally on valuable animals. Animals improve following transfusion but it is expensive and not practical if multiple animals are involved.
Most importantly, stress and movement of affected cattle should be minimised or their reduced ability to transport oxygen throughout the body may lead to collapse. They should be rested, nursed and given high quality feed. Handling of affected cattle should be avoided where possible; if movement or yarding is necessary, move animals slowly.
What is the DPI doing about the disease?
DPI is engaged in a collaborative research program with the University of Melbourne to gain a greater understanding of the disease and the causative organism.
How easily can the disease spread?
The disease is spread through cattle movements when cattle are carrying infected ticks. The disease is not transmitted directly between animals. Once diseased animals are on a property, the infected ticks multiply and spread the disease further to other animals on the property.
Are there quarantine restrictions from cattle coming into Victoria from northern NSW?
This disease is not a recent introduction into Victoria and has been endemic in Gippsland for several decades. Some cases in 'new' areas of the State may have been associated with movements from NSW, but it is highly likely that cattle moving out of Gippsland have also been spreading the disease. Cattle from endemic areas are usually immune and show very few symptoms, if at all. The tick responsible for carrying the disease (the bush tick) is found throughout much of Australia and has probably been here for hundreds of years.
Attempting to impose quarantine measures on the NSW border would therefore serve no purpose. Farmers need to practice good biosecurity - ascertain the status of source herds (for all diseases, not just theileriosis), and keep newly bought-in animals separate from the rest of the herd for two to three weeks.
Is benign theileriosis a notifiable disease?
Diseases are made 'notifiable' when (a) they need to be differentiated from other diseases of a more serious nature (for example exotic diseases), or (b) when the government intends to intervene and play a role in managing the disease. Given what is known abut the epidemiology of benign Theileriosis, in particular its widespread endemicity, regulatory intervention such as official quarantine and movement restrictions will not be effective in containment or control.
Nevertheless, reporting of the disease to DPI is encouraged in order to assist with research efforts and to monitor the situation.
Further information on benign theileriosis.
Information on benign theileriosis for vets.