Redwater Fever

Sylvaine Lacrosse BVetMed MRCVS, Molecare Veterinary Services

Colloquially known as Redwater, this blood-borne protozoal disease is also referred to as babesiosis. And whilst most would know the disease is spread by ticks, the actual culprit is the protozoa Babesia, which uses ticks as its vector, the most common in cattle in the UK being Babesia divergens.

A tick latches on to cows to feed on blood, if infected, they will also inject Babesia into the cows’ blood stream. Babesia multiplies inside red blood cells, eventually rupturing the cells and the broken down remainder leaking into the urine. This is called haemoglobinuria and causes the distinctive red urine giving babesiosis its name, Redwater.

When are cows most at risk?

Ticks prevail in warmer months, hence why clinical Redwater cases are typically seen in spring, summer or autumn. With climate change and unpredictability, the period of tick activity may even be prolonged and can put more areas at risk.

Any tick infested areas pose a threat to cattle, however cattle do develop immunity to the disease. Young animals appear to be refractory to babesiosis, which is why tick exposure when cattle are under 9 months of age is ideal for building up immunity and severe Redwater is usually seen in naïve adults. Introducing naïve animals to at-risk grounds is one of the biggest risks as the animals will not be able to mount a rapid enough immune response to Babesia.

What to look out for

A very small percentage of cattle will suffer fatal clinical signs, a much larger proportion will experience much more subtle subclinical signs including a mild fever, anorexia and ‘generally unwellness’. It is important that if your cattle are grazing tick-infested land and you notice any signs of poor health, Redwater should be in the back of your mind, even if you don’t actually see the classic red urine!

More severe clinical signs include:

-Anaemia

-Anorexia

-Pale/jaundiced mucous membranes

-Acute fever (up to 41°)

-Anal sphincter spasms and pipestream diarrhoea

-Severe dehydration

-Haemoglobinuria (broken down red blood cells in the urine)

–Babesia divergens identified on a blood smear (speak to your vet!)

Be aware of the clinical signs to look out for as the prognosis is significantly influenced by speed of diagnosis and treatment. Cattle have little to no chance of recovery once they exhibit signs of toxaemic shock, are unable to rise, have a low temperature and show behavioural changes suggesting brain damage.

Treatment

The antiprotozoal drug given to treat the babesiosis is Imidocarb. A significant factor with the use of this drug and one to not forget about, is that the meat withdrawal is 213 days!

As with most diseases, treatment also involves supportive therapy of the main clinical signs such as fluid therapy to combat the dehydration and in severe cases your vet may opt for a blood transfusion to deal with the anaemia. As with most diseases, early intervention increases chance of recovery.

How can I protect my animals?

At a higher dose, Imidocarb can also be used as a preventative measure, so if you are worried about naïve animals grazing at-risk land, speak to your vet and see whether this could be part of a plan to protect your animals. Again, do not forget about the meat withdrawal being just over 7 months! Because of this, the use of Imidocarb is not always ideal and protection requires other management.

The number of infected ticks influences the gravity of clinical signs, therefore removing potential tick habitats on grazing land would decrease the tick burden and protect the cattle. Such actions include reclaiming land covered in scrub, gorse and rushes. The smaller tick population would then allow a low level infection in cattle, enough for them to mount an immune response without experiencing severe clinical signs.

The most important factor to protecting cattle against babesiosis is the farmer themselves understanding the disease, knowing which animals are at risk and noticing clinical signs early enough for a successful intervention and improved prognosis.