Redwater Fever (Babesiosis)

Author: Richard Laven PhD BVetMed MRCVS
Reviewed: Richard Laven PhD BVetMed MRCVS 2017
Published: 2002

Babesiosis (Redwater fever)

This parasitic disease is usually first reported in May/June when its tick host first becomes active.

What is Babesiosis?

Babesiosis is an infection of the red blood cells by a single cell parasite of the genus Babesia. In the UK, babesiosis is usually caused by Babesia divergens. The disease is spread between cattle by ticks (Ixodes ricinus in the UK). The babesia is injected into the bloodstream by the tick and then invades the red blood cells and begins dividing, eventually rupturing the cell. Clinical signs begin around 2 weeks after infection.

Babesiois is rare except in known tick areas. However in these areas even though disease is often relatively mild there is a significant imact on productivity and fertility in affected cattle.

Clinical Signs

  • Increased temperature
  • Diarrhoea which ceases after around 36 hours and then becomes constipation
  • Red urine (due to haemoglobin produced by the rupture of the red blood cells) which becomes darker with time
  • Increased pulse rate
  • Abortion of pregnant cows
  • Death is rare in babesiosis in the UK


  • On the clinical signs described above
    • Recent movement to pastures known to harbour ticks
    • Blood smears can show up the parasite
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  • Mild cases may recover without treatment.
  • More severe cases need treatment. This is often best combined with a preventative treatment for the as yet unaffected cattle. This choice is best made on an individual farm basis in consultation with your vet.


  • Identification of risk areas
  • Prophylactic treatment of cattle about to be moved to a risk area
  • Tick control
  • Vaccine not yet available in UK


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