Tick Fever in Cattle
What is Tick Fever?
Tick fever or ‘red water’ is a disease of cattle that is transmitted by the cattle tick (Boophilus microplus). This disease is caused by one of three blood parasites Babesia bovis, Babesia bigemina, or Anaplasma marginale that use the cattle tick as host. Babesia bovis causes the majority of tick fever deaths in our local area and is responsible for approximately 80 per cent of reported cases.
Clinical Signs of Tick Fever?
Outbreaks of Babesiosis are normally severe and large numbers of stock can get sick and die.
The initial clinical signs of Tick Fever include a fever (normally above 40 degrees Celsius), loss of appetite, depression and reluctance to move. Unfortunately these early signs are very similar to that of Bovine Ephemeral Fever (3 day Fever) which often delays diagnosis. Other signs include the passing of red urine, jaundice, anaemia and eventual death.
Babesia bovis is known for causing nervous signs such as aggression, hypersensitivity, convulsions and paralysis. Once nervous signs are evident the disease is almost always fatal.
What stock are susceptible to Tick Fever?
All cattle that graze tick infested country in northern and eastern Australia are at risk of contracting tick fever. Although Bosindicus (Brahman cross) cattle are less susceptible to Babesia bovis than European and British breeds they are still involved in 1 out of 5 outbreaks and Brahman breeds are very susceptible to Anaplasma marginale.
Calves from immune or vaccinated mothers do receive temporary protection from their mother’s milk (maternal protection). This protection lasts about 3 months, which is followed by an age resistance that lasts until most calves are about 9 months of age. Calves infected with tick fever when their age or maternal protection is high often show no signs of disease and develop long term immunity to tick fever without the need for future vaccination. However stock that are not infected with tick fever in the first 9 months as calves become very susceptible to tick fever as their age resistance wanes and producers have no way of identifying those protected and those not without physically vaccinating all stock.
How do we prevent Tick Fever?
By far the most reliable method of preventing economic losses from tick fever is vaccination. Chilled Trivalent (3-germ) tick fever vaccine is the vaccine recommended for cattle producers in our area as it protects against all three organisms that cause tick fever (Babesiabovis, Babesiabigemina and Anaplasmamarginale).
Vaccinated animals undergo mild reactions to the vaccine but the immune system is stimulated to produce long-term (usually life-long) protection against the disease and full immunity is present 8 weeks after vaccination. Although cattle of any age can be vaccinated we recommend vaccinating animals at 3-9 months when there is little risk of reactions to the vaccine. The risk of reactions is greater when vaccinating adult cattle, especially bulls and pregnant cows, and they should be closely observed for the 2 month reaction period.
For local producers our recommendation is to vaccinate all calves during winter after weaning when the tick numbers and stress levels are low.
For further advice please call Vet Cross and talk to one of our Veterinarians.