This spring we have already seen several cases of ‘redwater’ in cattle (also known as babesiosis), and surely more will follow. Redwater is caused by the Babesia parasite, which is carried and spread by ticks. When the adult tick bites the cow, the babesia parasite enters the blood stream and invades the red blood cells, where it multiplies. Eventually the red blood cells rupture (this is called haemolysis), resulting in the typical symptoms of red urine (due to haemoglobin in the urine), fever, anaemia (pale membranes in the eyes and vulva), weakness, increased heart rate, diarrhoea followed by constipation, and in severe cases death. Treatment consists of an injection of imidocarb (Imizol®) to kill the parasites and in severe cases a blood transfusion is needed, however this will not always save the animal.
The redwater season coincides with the peak in adult tick activity, which is usually in spring and autumn, but depends very much on rainfall and temperature. Clinical cases in spring usually start about 2 weeks after air temperature reaches 7 to10°C. Changing weather patterns have also caused tick habitat to spread to areas that used to be tick-free, and the Babesia parasite has followed. Ticks carried on deer are thought to help more the parasite to new areas.
Very young animals seem to be quite resistant to the disease, but we are unsure how long this natural protection lasts. After exposure, animals build up immunity against the parasite, and therefore cattle that have been gradually exposed from a young age ‘should’ cope well.
It is the naïve older animals we are most worried about. Non-immune adults brought into a redwater area from a non-endemic area are at highest risk of severe disease and should be protected – we have seen cases of adult dairy cattle purchased at dispersal sales succumbing to redwater. In addition, cattle on farms that border endemic areas may get fluctuating exposure, with insufficient immunity build-up, resulting in clincal cases.
We have several tools available to prevent disease: good tick control from early in the season, strategic grazing, redwater vaccination and preventive imizol treatments. Some farms have to use all the above to prevent cases, so it is advisable to consult your vet for a good prevention strategy
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