Tick fever

(Babesiosis and Anaplasmosis)

Tick fever is caused by infection with Babesia and Anaplasma organisms transmitted by the cattle tick Rhipicephalus australis (formerly known as Boophilus microplus). All cattle in tick infested areas are at risk of developing tick fever. Breed and age are key risk factors.

British, European and other Bos taurus breeds are more susceptible to tick fever caused by Babesia than Brahman/Bos indicus breeds. All breeds, including Bos indicus breeds, are highly susceptible to disease caused by Anaplasma marginale.

There is a strong link between age and resistance. Calves exposed to tick fever organisms between 3-9 months of age rarely show clinical symptoms and develop a solid, long-lasting immunity. Once infected with Babesia or Anaplasma organisms, the animals become carriers and the infection and immunity is likely to persist for many years. A tick fever vaccine is available in Australia.The single biggest risk for disease caused by infection with tick fever is in cattle which are introduced from outside the cattle tick areas. However, even cattle born and raised within the tick area are not guaranteed to have developed immunity by the time age-related resistance wanes at 9-10 months of age.

Figure 1. Tick fever is transmitted by cattle tick. Naïve cattle which are introduced into the cattle tick zone are at greatest risk. Image courtesy of Virbac

Signs

Signs of tick fever are often non-specific and can include depression, loss of appetite, weight loss, fever, anaemia, jaundice, abortion, recumbency (lying down and unable to rise), and death. Cattle with Anaplasmosis (one of the causes of tick fever) can also become constipated. The passing of red urine (red water) is a sign of a number of disease conditions in cattle including tick fever. These diagnoses need to be confirmed either with a stained thin blood film examined under the microscope, or from blood samples sent to the laboratory.

Diagnosis

If tick fever is suspected, contact a veterinarian for expert assistance. Microscopic examination of blood and organ smears from sick or dead animals is the most commonly used procedure to confirm tick fever.

Tick fever vaccine

Effective vaccines for tick fever are available in Australia, which almost eliminate the risk of disease. Vaccinating against tick-borne diseases provides some degree of tolerance for infestations.

The trivalent tick fever vaccine is a live, whole organism, blood-based vaccine containing attenuated strains of B. bovis and B. bigemina as well as Anaplasma centrale. The vaccine is mostly sold in a chilled ready-to-use form with just a short 4-day shelf life.

Cattle of any age can be vaccinated, but it is best to vaccinate animals between 3-9 months of age when the age-related resistance is present and there is little risk of reactions to the vaccine. Many producers find it convenient to vaccinate around weaning time. It takes about 3-4 weeks after vaccination for immunity to develop to babesiosis and up to two months for immunity to develop to anaplasmosis.

When introducing cattle from outside the tick areas which have never previously been exposed to tick fever organisms, keep in mind this time taken for immunity to develop after vaccination. Ideally, vaccination occurs well before introduction to allow time for immunity to develop to all components of the vaccine.

Figure 2 Tick fever vaccine. Image courtesy of the Tick Fever Centre

Treatment

  • If tick fever is suspected, contact a veterinarian for expert assistance.
  • Treat as soon as possible, or animals may not recover.
  • Have the diagnosis confirmed at a laboratory via examination of blood smears prepared from the tip of the tail or ear, taken before, or at the time of treatment. In the case of dead animals, organ smears (including brain smears) and blood smears can be taken.
  • Use an acaricide to remove ticks from all animals to reduce the risk of a secondary outbreak.

Contact the Tick Fever Centre for advice

You can contact the Tick Fever Centre for advice about:

  • Diagnosis of tick fever.
  • What samples to collect in your situation.

Tick Fever Centre

Phone: (07) 3898 9655

Email: tfc@daf.qld.gov.au