Babesiosis - Cattle

Also known as: Redwater fever — Redwater

Introduction

Babesia is a protozoan parasite that is transmitted by the Ixodidae family of hard ticks.

It is prevalent in the UK and worldwide with different species of ticks involved in different regions of the world. Unlike some other protozoal diseases, adults are most severely affected, with calves less than 9 months of age being refractory to the disease.

The epidemiology of the disease is determined by the number of infected ticks seeking a blood meal at that time. Protective immunity can be achieved from dams that have a carrier state. Cattle can become clinically infected though, without showing any clinical signs and this usually occurs at a young age. If calves less than 9 months are affected, no clinical signs will usually be seen and these cattle will then develop and immunity for life. In tick infested regions, most cattle become immune as calves and clinical disease is rarely seen on such farms. In some cattle, immunity may wane when re-infection does not occur for a long period.

The disease varies in form worldwide due to different species of Babesia and different climates. In the UK, sporadic disease occurs leading to enzootic instability as immunity may be established in the case of an outbreak but will then wane if no re-infection occurs for a number of years. When the disease does appear, it occurs mostly during the spring and autumn during periods of greatest tick activity and mostly in stressed cattle under 2 years old on rough grazing.
B. divergens is the most common species in the UK. Ixodes ricinus is the vector and trans-ovarial transmission to the next generation occurs.
B. major occurs in South East England but is not pathogenic. The vector here is Haemaphysalis.

Overseas, B. bovis causes considerable losses in cattle in many tropical and sub-tropical areas. The vector here is Boophilus. B. bigemina causes problems in Africa and South America where the vector is also Boophilus.

Predisposing factors to the disease include;

• Susceptible animals introduced into an infected area
• Infected ticks introduced into a clean area
• Infected cattle introduced into an area with clean ticks
• Temporary reduction in the tick population decreasing the transmission rate (causing enzootic instability)
• Infected cattle are transported or stressed in other ways, e.g. parturition

Clinical Signs

The first signs are usually of general depression with pyrexia and 'pipe-stem' diarrhoea due to constriction of the anal sphincter. Haemoglobinuria will also be present but may not be noted at that time. Later the mucous membranes will appear noticeably pale due to anaemia and diarrhoea will change to constipation.

It can be of a very sudden onset and this disease can be fatal. Pregnant cows will normally abort if infected during pregnancy.

Diagnosis

There is often a history of movement of the cattle to tick infested pasture.

Presence of haemoglobinuria should lead to a short differential list, with Babesia being most common. Elimination of other differentials will often lead to a diagnosis of exclusion.

Blood samples should be taken if haemoglobinuria is not present and smears should be made from these.

Treatment and Control

The only licensed treatment for babesiosis is Imidocarb.

Supportive care such as fluid therapy or blood transfusion if very severe, is also required.

Vaccines have been developed in South America and Australia, but currently a vaccine has not been designed from B. divergens although research is being undertaken into this.

References

Andrews, A.H, Blowey, R.W, Boyd, H and Eddy, R.G. (2004) Bovine Medicine (Second edition), Blackwell Publishing

Fox, M and Jacobs, D. (2007) Parasitology Study Guide Part 1: Ectoparasites Royal Veterinary College

Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences

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