Surveillance Focus: Babesiosis/Redwater fever in cattle
Babesiosis is a disease caused by a single-celled parasite (Babesia divergens in the UK) which infects red blood cells, eventually causing them to burst. It is spread by infected blood-sucking ticks and, although is often a mild disease, can have a significant impact on productivity and fertility. The disease is usually seen in adult cattle since calves under nine months are innately resistant and also often have some protection from maternal antibodies on Babesia-infected farms.
Clinical signs begin about 2 weeks after infection, and include a sudden fever, diarrhoea followed by constipation, red urine (caused by the haemoglobin pigment from the burst red blood cells), anaemia (with rapid pulse, fast breathing and pale membranes), milk drop, depression and weakness, and abortion of pregnant cows. Diagnosis is made on clinical signs, a history of grazing tick pastures, visualizing the parasite under the microscope in blood smears or PCR of blood samples. Treatment is possible. There is no vaccine, although repeated exposure means immunity develops over time on infected farms. Naïve adult cattle bought into infected herds are particularly at risk of disease, as are naïve herds grazing on newly-acquired tickinfested land.
Babesiosis is usually seen from May to November when the tick host (the sheep tick, Ixodes ricinus, in the UK) is active and herds are out at pasture.
Babesiosis, along with other tick-borne diseases, is endemic and widespread in parts of the west country, Cumbria and upland areas of Wales, but has also been diagnosed in other areas of the country including Staffordshire. As our climate changes and ticks spread geographically and increase in number, this is a disease to watch out for. If you notice any suspicious signs in your cattle, especially if they are grazing tick-infested pastures, please do contact us and speak to one of the vets.
During this grazing season, until autumn 2021, the APHA are offering free PCR testing for babesiosis on blood samples. These can be submitted from up to three cattle displaying clinical signs of babesiosis per farm. Both beef and dairy animals at grass can be sampled, and the full animal ear tag number and the OS map reference/what3words address of the affected grazing field will need to be included.
The information gathered will contribute valuable surveillance data on babesiosis and other tick-borne pathogens in different regions of GB. All data will be anonymised for inclusion in this study. The APHA may also contact participating vets/farmers to collect further epidemiological data to help them understand risk factors for redwater in cattle, and why prevalence varies across different areas of Great Britain.
As always, if you’re concerned, please don’t hesitate to contact the team.
Header image Babesia divergens (piroplasm stage) infecting red blood cells of a cow. Giemsa stained.
Image courtesy of Alan. R. Walker, licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.