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Tick fever in Australia

Tick fever is a cattle disease caused by any one of the following blood parasites:

  • Babesia bovis
  • Babesia bigemina
  • Anaplasma marginale.

These parasites are all transmitted by the cattle tick (Boophilus microplus). Disease caused by Babesia bovis or Babesia bigemina is called babesiosis, often referred to as 'red water'. Disease caused by Anaplasma marginale is called anaplasmosis.

Babesia bovis is the most important parasite, causing more than 80% of outbreaks of tick fever in Queensland each year.

Clinical signs of tick fever

Signs of tick fever include:

  • weakness
  • depression
  • loss of appetite.

These signs are mainly due to the associated fever and red blood cell destruction (causing anaemia).

Despite the common name 'red water', red urine is only occasionally present and late in the course of the disease. Other clinical signs may include jaundice and neurological signs.

Cattle with Babesia bovis infections may be quite sick even in the absence of anaemia and red urine.

Diagnosing tick fever

It is difficult to diagnose tick fever based on clinical signs alone.

The best way to diagnose tick fever is to send blood smears to a laboratory for examination.

Risk factors for tick fever

Breed

British, European and other Bos taurus cattle breeds are more susceptible to tick fever caused by Babesia organisms than Brahman and Bos indicus breeds. Cross breeds (Bos taurus x Bos indicus) have intermediate susceptibility determined by the percentage of each breed type.

All breeds, including Bos indicus breeds, are highly susceptible to disease caused by Anaplasma marginale.

Age

There is a strong link between age and resistance. Most outbreaks occur in animals 18 to 36 months of age. Calves exposed to tick fever organisms between 3 to 9 months of age rarely show clinical signs and develop a solid, long-lasting immunity.

Exposure

Cattle born and raised in areas where cattle ticks are endemic can develop natural immunity through exposure to ticks infected with tick fever.

However, exposure of calves to ticks infected with tick fever (and subsequent development of protective immunity) can be highly unpredictable. Exposure is influenced by factors such as breed, season and tick-control strategies.

All cattle raised in areas free from cattle ticks are at risk of tick fever if introduced into areas where ticks are present.

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