Babesiosis is caused by the infection of red blood cells by this single cell parasite. It is transmitted by ticks and once in the bloodstream it multiplies in red blood cells, which causes them to burst.
As a result, haemoglobin, which is usually contained in the red blood cells enters the blood and as the kidney cannot filter out this small protein, haemoglobin gets into the urine. Red coloured urine is, therefore, a telltale sign of the disease.
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The lifecycle of Babesia involves both ticks and cattle. Infection can be passed from adult ticks to their offspring allowing the disease to persist in the environment even without cattle being present.
Franz Brulisauer, SRUC veterinary centre manager says: "The disease is rare except in known tick areas. It is particularly a concern in the southwest of England. However, cases of red water are also now being reported in Scotland and Wales.
"Although the disease is often relatively mild there is a significant impact on productivity and fertility in affected cattle. Clinical disease is seen most often in adult cattle as calves have innate immunity.
"Most at risk are animals which move from a region without Babesia, to one where this blood parasite is endemic. Unfortunately, immunity is not life-long and in the absence of re-infection boosting the immune system, animals will become susceptible again. Clinical signs begin around two weeks after infection."
Symptoms
- High fever, although sometimes animals can have normal or subnormal temperatures.
- 听Diarrhoea which may be followed by constipation after around 36 hours.
- Red urine, due to haemoglobin produced from ruptured red blood cells, which becomes darker with time.
- 听Increased heart rate and weakness
- Anorexia, dehydration, and depression, lack of appetite and general lethargy.
"Babesiosis is not necessarily lethal, but SRUC Veterinary Services have dealt with cases reported as sudden deaths without prior clinical signs. Interestingly, in one such case the farmer noticed red urine pouring from the carcase when being lifted by a tractor.
"Typically, animals are described as dull, anorexic, and/or anaemic, with weakness or recumbency. Some animals experienced weight loss, nervous signs and a starey eyed appearance. Babesiosis is potentially zoonotic but human cases are thankfully rare," says Mr Brulisauer.
Babesia prevalence
Although SRUC Veterinary Services have not diagnosed many cases, there has still been a noticeably increase in the numbers of Babesiosis diagnoses in recent years. Most cases have been diagnosed between May and October, consistent with the period of highest tick activity. Cases, however, have also been recorded in winter and January is the only month without diagnoses, so far.
According to the APHA Scanning Surveillance Dashboard which reports livestock disease in GB there were nine cases diagnosed in 2020, 47 in 2021 and 27 both in 2022 as well as 2023.
Mr Brulisauer says: "When interpreting scanning surveillance data, we must bear in mind how these data have been collected. These are self-selected samples, meaning it takes first a farmer to get concerned about health of their stock to the point to get their vet involved. The vet then needs to decide that the clinical suspicion should be confirmed by either an APHA or SRUC lab.
"It is easy to see that once farmers and vets get used to see babesiosis in certain geographic areas, they will go straight to therapy and leaving out the confirmation step when the clinical signs, in particular red urine, are noticed.
"It therefore seems fair to assume that even with plateauing cases year on year, babesiosis cases continue to be diagnosed in areas where farmers and vets may not commonly see the disease."
The increase in Babesia is thought to have been caused by:
- Susceptible, possibly recently purchased cattle going on to fields with infected ticks and becoming infected.
- Changes in land use, notably forestation, offer tick habitats and previously unexposed cattle get infected with Babesia.
- Wildlife moving infected ticks.
- Climate change can improve conditions for ticks and alter tick distribution and period of tick activity. Furthermore, the length of the grazing season may increase, which in turn increases the risk period for exposure to ticks.
Diagnosis
Diagnosis of babesiosis is based on clinical signs, history of exposure to tick-infested areas, and laboratory tests. Blood smears can show up the parasite and a vet can take blood samples from live cases of suspected babesiosis. Postmortem can confirm babesiosis and rule in/out other differential diagnoses.
Treatment and prevention
Mild cases of babesiosis may recover without treatment, but more severe cases will require prompt veterinary attention. This is often best combined with a preventative treatment for the as yet unaffected cattle. It is worth noting that sheep are resistant to infection with Babesia divergens so could be used to graze high risk fields but, in the absence of cattle, the parasite can persist in ticks for at least two generations.
Controlling and preventing this disease is best made on an individual farm basis in consultation with your vet and can include the identification of risk areas and the prophylactic treatment of cattle about to be moved to a risk area. Tick control is advisable, however, a vaccine is not yet available in the UK.
Mr Brulisauer says: "Babesiosis remains a significant concern for cattle farmers in the UK, particularly in regions with high tick populations. The risk of exposure to other tick-borne diseases should also be considered and you need to speak with your vet about treatment and prevention suited to your farm.
"Effective management and control strategies are essential to minimise the impact of this disease on cattle health and productivity. Ongoing research and advancements in diagnostic and preventive measures continue to improve the outlook for managing babesiosis in the UK."
Ticks and tick-borne diseases (TBDs) are of growing concern in the UK with TBD outbreaks appearing in new areas, posing threats to livestock and public health. In response to this issue the Scottish Environment, Food and Agriculture Research Institutions (SEFARI) Gateway funded an Innovative Knowledge Exchange workshop at Moredun Research Institute, Edinburgh, to identify best practice and produce industry guidelines for ticks and TBD control.
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