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Babesiosis (redwater)

Babesiosis is caused by an intra-erythrocytic protozoan of the genus Babesia transmitted by hard ticks of the family Ixodidae

Unlike many other parasitic diseases, it affects adults more severely than young cattle in which infection is frequently subclinical. It causes fever, haemoglobinaemia, haemoglobinuria, anaemia and death.


Aetiology and epidemiology

The four most important species of Babesia that affect cattle are B. bovis, B. bigemina, B. divergens and B. major, the first three being much more significant than the last.

The epidemiology of the Babesia spp. is governed by the local climate and behaviour of its tick vectors.


Tropical species: B. bovis and B. bigemina. These species are found in Australia,Africa, South and Central America, Asia and the very south of Europe. In Australia and the America the tick Boophilus microplus is the sole vector, in Africa other Boophilus and Rhipicephalus species. Boophilus spp. are one-host ticks, i.e. all stages of the life cycle take place on one animal, only the engorged female dropping to the ground before laying eggs. Some vectors in Africa, e.g. R. evertsi, are two-host and R. appendiculatus is a threehost tick.

Parasitaemia in venous blood is low with B. bovis but it may be high in capillaries and cause sludging of blood, which if in the brain causes early death. It also produces enzymes with severe effects on the blood coagulation system, and is generally considered the most pathogenic of the bovine Babesia spp.

Babesia bigemina infection results in much higher venous parasitaemia but it has few other effects other than to cause a febrile reaction and straightforward haemolytic anaemia.

Temperate species: B. divergens and B. major. Babesia divergens, is common in areas of permanent pasture in northwestern

Europe and is transmitted by the three-host tick Ixodes ricinus. Babesia major (3.2 = 1.5mm) is found only in south-eastern England and on islands off the coast of The Netherlands and is transmitted by Haemaphysalis punctata. Babesia divergens behaves rather similarly to B. bigemina, i.e. it can cause a high parasitaemia, which results in fever and severe haemolytic anaemia. It has little effect on blood coagulation systems in comparison to B. bovis. Its epidemiology is closely bound to the

ecology of its vector I. ricinus. In Europe, I. ricinus is generally active only between May and November, and in most areas has spring and autumn population increases, although in the most northerly climates it may only have one in midsummer. The ticks quest more actively in warm conditions and outbreaks of babesiosis are frequently observed two weeks after fine

weather. The epidemiology of B. major is still only slightly investigated, but such isolations as have been reported have taken place in May and June.




  • Slight dullness
  • Pyrexia 40.5–41°c (105–106°f)
  • Diarrhoea (pipe-stem diarrhoea).
  • Haemoglobinuria
  • Slight dehydration
  • Sunken eye


Mid: After 24–36 hours:  

  • Mucous membranes tend to become pale
  • Pulse rate is increased
  • Animals tend to slow up
  • Reduction in appetite and thirst
  • Urine tends to become very dark in colour and reduced in quantity
  • Faeces may return to normal


Late: In another 24–36 hours:

  • Rectal temperature is often subnormal
  • Blanched mucous membranes
  • Poor appetite and drinking little
  • Marked constipation
  • Greatly increased heart rate
  • Pregnant cows may abort



  • The carcass may be very blanched and there is sometimes jaundice
  • The liver is often swollen and pulpy, with the kidneys dark and enlarged
  • The bladder contains red-brown urine
  • There are ecchymotic haemorrhages under the epicardium and endocardium



history of recent movement to tick-infested pastures

Clinical babesiosis is unlikely to be observed in cattle less than nine months old; such cattle can be infected and show febrile reactions but the

resultant parasitaemia remains low and haemoglobinuria

mild. In areas of large tick populations, most cattle

are infected at an early age and become immune thereafter,

the situation being described as enzootic stability.

In the early stages of the disease, haemoglobinuria may

not be present and diagnosis requires careful examination

of stained blood smears (see Fig. 45.1). Once

haemoglobinuria is present, the parasitaemia may be

more obvious. Differential diagnosis requires elimination

of other conditions causing haemoglobin uria, e.g.

anaplasmosis (p. 761), eperythrozoonosis, leptospirosis

(p. 734), postparturient (p. 792) and bacillary haemoglobinuria

(p. 719).


Treatment and control

There are two aspects to treatment:

firstly, treatment with a babesicide secondly, the need for supportive therapy such as blood transfusion and fluid replacement. There are few babesicides now available. The only treatment now licensed in the UK is imidocarb, which is given at a dose rate of 1mg/kg body weight. It is used widely in South America and other countries. It is highly effective and relatively non-toxic, but does have tissue residues for several weeks after its use. It can also be used at twice the therapeutic dose as a chemoprophylactic, giving protection from infection for up to six weeks. It is used in this way to administer to cattle that will be exposed to ticks, or that have been vaccinated with live Babesia with the hope that cattle will become mildly affected but protected from clinical illness and immunity to further infection will be stimulated.

Live vaccines for B. bovis and B. bigemina have been available in many countries for many years, notably Australia and South America. For B. bovis the vaccines consist of live organisms made avirulent by repeated rapid syringe-passage through splenectomized calves.

In the case of B. bigemina rapid passage did not reduce virulence and vaccines available are either developed by ‘slow’ passage from recrudescences of parasitaemia or are fully virulent organisms, which are used in schemes involving infection and subsequent treatment.

There are no vaccines currently available for B. divergens, although much research is being carried out to develop inactivated recombinant vaccines for that species and B. bovis and B. bigemina.

Blood transfusion is frequently required for severely affected adult cattle and is normally achieved by collection of 5 l of blood from an unaffected healthy cow into a 22 per cent solution of the anticoagulant acid citrate dextrose (ACD), the mixture being immediately transfused into the recipient animal. Such single transfusions without cross-matching of blood are usually successful, but repetition can lead to problems of incompatibility of blood antigens.



Babesiosis is caused by an intra-erythrocytic protozoan of the genus Babesia transmitted by hard ticks of the family Ixodidae

Unlike many other parasitic diseases, it affects adults more severely than young cattle in which infection is frequently subclinical. It causes fever, haemoglobinaemia, haemoglobinuria, anaemia and death.

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