Babesiosis (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 organism called Babesia bovis and Babesia bigemina. Anaplasmosis is another important “tick fever” caused by an organism called Anaplasma.
What to look for
Signs range from minimal illness to severe disease and death:
• Red urine (“redwater”)
• High fever and a drop in milk production
• Nervous signs
• Anaemia and jaundice
Cause – infection with a protozoan organism
Babesia must complete part of their life cycle outside cattle, and are transmitted from animal to animal by cattle ticks (especially Rhiphicephilus microplus). Adult ticks draw in Babesia organisms when sucking blood from cows. The ticks then drop off the cow and lay eggs which hatch in the environment. Immature ticks harbour Babesia organisms in their salivary glands ready to be injected when they start to suck blood from a cow. Once injected into cattle they multiply inside red blood cells and then burst out of the cells. If this process continues for some time animals can become anaemic. Cows usually start to show signs of illness 2 weeks after they become infected. Cows can remain infected with Babesia for several years.
Animals likely to be affected
Tick fever is unusual in animals under 9 months of age. British breeds of cattle are more likely to be infected than Bos indicus breeds.
Other diseases with similar signs
In sub-tropical regions tick fever can be confused with other conditions that cause depression and red water, for example, copper poisoning, bracken fern and other plant poisonings. While anaplasmosis may resemble tick fever, affected animals rarely have blood in their urine.
Confirming the diagnosis
Examination of blood smears in a laboratory
Your vet can prescribe drugs that treat sick animals and also provide protection for several weeks.
The 3 main approaches to controlling the impact of tick fever:
• Control tick numbers
• Expose young animals to tick fever organisms when they are less than nine months of age. These animals are unlikely to show clinical signs of infection and can be expected to remain immune for several years.
• Vaccination. Some animals may have a bad reaction 1-3 weeks after vaccination so observe recently vaccinated animals closely and promptly treat any that show signs of disease.