Anaplasmosis (tick fever)
Tick fever occurs only where cattle ticks are found, in the subtropical and tropical regions of Australia. Cattle ticks should not be confused with bush ticks which are found over a much wider area. There are several forms of “tick fever”. The disease discussed here is caused by an organism called Anaplasma. Babesiosis is another important “tick fever” caused by two organisms called Babesia bovis and Babesia bigemina.
What to look for – most cases are mild
- Anaemia - paleness of the lining of the mouth and the udder
- Jaundice – yellowish tinge to skin and mucous membranes
- Fever and a drop in milk production
- Laboured breathing or cattle get out of breath easily when moved
- Pregnant cows may abort
- Occasionally fatal
Cause – a tick-borne protozoa
Anaplasma marginale belongs to the protozoa group of organisms. Cattle become infected with Anaplasma when bitten by cattle ticks. Anaplasma penetrate into red blood cells, multiply and destroy the red blood cells. Animals usually stay infected for long periods (possibly for life) but may not show any signs of disease.
Animals likely to be affected
Animals can be infected at any age but, especially in young animals, the disease may not be obvious. The most severely affected animals are usually mature lactating cows.
Other diseases with similar signs
Other conditions that cause depression and anaemia in sub-tropical regions e.g. copper poisoning, bracken fern and other plant poisonings, Babesiosis. It is unusual to see blood in the urine whereas this is a common sign of Babesiosis and bracken fern poisoning.
Confirming the diagnosis
Laboratory examination of blood smears
Spread of the disease
Cattle ticks (especially Rhipicephilus microplus)
Antimicrobial injections can improve the condition of seriously infected animals.
- Expose young animals (< 9 months of age) to tick fever organisms in areas where tick fever occurs. Early exposure is unlikely to cause clinical signs of infection and may provide immunity for several years.
- Control ticks – reducing the number of ticks reduces the chance of animals becoming infected with tick fever.
- Vaccinate non-exposed animals that are being introduced into areas where tick fevers occur. Vaccinated animals should be closely observed 1-3 weeks after vaccination as some animals may have a bad reaction.