Babesiosis or Redwater is a very severe disease, considerably more so than Anaplasmosis.This is a fever producing disease of cattle, caused in Africa by the protozoan parasites Babesia bigemina and Babesia bovis. The disease occurs worldwide but has serious implications in the tropics because of the high prevalence of the host ticks. Other names of this disease are Red water and Cattle tick fever.

Babesiosis parasites are spread only through their carrier tick. Ticks acquire babesia infections from infected animals

In Africa, the Cattle tick which transmits B. bovis was introduced at the end of the 19th century. B.bovis thus only occurs in those areas of Africa to which Cattle tick has spread. In Kenya the Blue tick, Boophilus decoloratus, which is the main transmitter, can only transmit B. Bigemina and as a result this species assumes more importance than B. bovis

Tranmission occurs transovarially, that is, from the maternal body to eggs within the ovaries. In areas where Babesiosis occurs,two features are important in determining the risk of the disease occuring

• 1) Calves have a degree of immunity (related both to colostral-derived antibodies and to age) that persists for about 6 months.
• 2) Animals that recover from Babesia infections are generally immune for life

Thus, where there are high levels of tick infestation, all newborn calves will be infected by Babesia parasites by 6 months of age. On recovery from initial infection they are immune but harbour the parasite (premune) and may remain carriers for up to 2 years. In areas where Babesiosis is prevalent, constant reinfection ensures that such cattle remain carriers permanently, although the premunity may break down due to other factors such as stress or other diseases occuring at the same time, resulting in clinical babesiosis.

This stability can be upset by either natural factors such as seasonal variation or artificial factors such as drought, dipping etc. Reduction in tick numbers to levels such that tick transmission of Babesia to calves is insufficient to ensure all are infected during this early critial period. In this case some animals remain at risk. If these are infected as adults, they may suffer severe clinical reactions.

Thus in enzootic areas:

• 1) Enzootic stablity:- The continuous presence of Babesia in both cattle and ticks with frequent acquisition of the parasite from active infective ticks ensures that cattle are infected in calfhood and remain carriers due to contant reinfection.Under these conditions clinical babesiosis is minimal.
• 2) Enzootc instability:-The infection of Babesia is such that not all cattle are infected as calves, and therefore some animals remain susceptible. If these are infected as adults, they may suffer severe clinical reactions. Such conditions arise when the number of ticks fluctuate due to factors such as seasonal variation, drought, dipping etc.

The incubation period ( the time from tick attachment to the appearance of parasites in the red blood cells) is normally in the range of

• 8-16 days for B.bovis as transmission occurs early larval stages of ticks
• at least 9 days longer for B.bigemnia because infection is not transmitted until the nymph and adult stages of the tick begin to feed.

Ticks acquire babesia infection from infected animals.

Babesiosis or Redwater is a very severe disease often confused with but more severe than Anaplasmosis.The first indication that the disease is present may be finding of a dead animal - usually an adult - in the paddock.

The parasites invades the red blood cells where they multiply and break out to invade more red blood cells. The released parasite and host constituents from the destroyed red cells are toxic, resulting in shock, anaemia and short supply of oxygen to tissue.

The release of haemoglobin results in jaundice and blood in the urine. The urine is usually, but not always, red in colour. Sometimes the urine is dark red and sometimes it can be almost black. Such animals are very ill indeed and usually die.

There is a rise in temperature. This is often 41C (106 F) or higher. Affected animals become depressed, listless, rumination ceases, milk yield drops, and they refuse to eat. Pregnant animals often abort.

The eyes and gums are pale from anaemia and jaundiced, due to bile pigments in the blood stream.

In severe cases, brain capillaries become blocked with infected red blood cells causing cererbal babesiosis resulting in incoordination followed by posterior paralysis,or by mania,convulsions and coma. Such animals rarely recover, despite treatment.

In less severe cases of the disease, infected cattle have fever lasting about 1 week and remain sick for 3 weeks. This group of animals may recover slowly while pregnant animals may abort. Recovered animals remain permanent carriers of the disease. Zebu cattle appear to have more resistence to babesiosis than do European breeds.

Post mortem fndings reveal an enlarged spleen, a swollen liver, with an enlarged gall bladder containing dark green granular bile, congested dark-coloured kidneys, and generalised anaemia and jaundice. The urine is usually, but not always, red in color.

The diagnosis can be confirmed in a laboratory by the examination of a stained blood smear taken from the ear or tail tip. A number of serological tests are available but generally these are out of reach under local conditions. Under the microscope B. bigemina parasites are large organisms, seen within the red cells in pairs at an acute angle to each other. B. bovis are small and lie at an obtuse angle to each other.

A number of serological tests are available such as the indirect fluorescent antibody test, ELISA and the complement fixation test, but generally these are out of reach under local conditions.

Other diseases must be considered when an animal is seen to be passing red urine. Possibly the most important of these are:

• Leptospirosis. This disease also presents with red urine, jaundice, abortion, depression and loss of appetite. However there are no blood cells in the urine, it affects all ages, including young calves and the degree of jaundice is often more profound due to the more chronic nature of the disease. Sensitivity to light of white skin is common. Leptospirosis often occurs during periods of heavy rain as rodents frequently are carriers, passing the infection in their urine, which can then survive for extended periods of time in pools of water.
• Heartwater may also initially be confused with cerebral babesiosis but there are clinical differences and no babesia parasites will be found in stained smears.
• Anaplasmosis is a less severe disease with no blood cells in the urine.

At the moment in Kenya prevention must rely on tick control and trying to reach a situation of enzootic stablity by aiming to control the ticks but not the disesase they transmit so that young stock are infected and develop a lifelong immunity. This can be difficult in areas where other ticks transmitting other diseases such as East Coast Fever occur. The Blue tick is normally the first tick to develop resistance to new acaricides. The results of this resistance can be catastrophic

It is advisable to keep suitable breeds of animals in areas where the disease is prevalent. Such breeds may include indigenous cattle and their crosses with exotic cattle. With these breeds the dipping or spraying intervals can be extended as these local breeds have more resistance to babesiosis and also to ticks, but with European breeds, tick protection is required.

The whole picture must be considered before taking any decision regarding extension or reduction of dipping or spraying intervals.

Vaccination using live, attenuated strains of the parasite has been used successfully in a number of countries. Combined vaccinaton and strict control of ticks is an effective control strategy when exotic cattle are introduced. Young animals can be vaccinated with live vaccines to counter periods of inactivity of ticks. These techniques are currently unavailable in Kenya so a carefully monitored tick control program is required to allow the development of resistance in conjunction with the control of other tick-borne infections.

Two drugs are currently available for the treatment of Babesiois. These are;

• Diminazene aceturate (Norotryp, Berenil etc) and
• Imidocarb dipropionate ( Imizol).

Dimiazene is given at a dose rate of 2 to 5mg/kg by intramuscular injection.

Imidocarb is given at a rate of 1.2mg/kg by subcutaneous injection.

Higher doses of both drugs will protect animals for several weeks.

Large species of Babesia such as Bigemina are more responsive to treatment than the small species such as Bovis which may require a larger dose of the same drug to effect a cure. Fortunately Bigemina is the more common species in Kenya.

The aim of treatment is to promote recovery from the clinical disease while allowing some organisms to persist in order to allow the animal to develop an immunity to the disease. Too rapid a cure can result in the animal being susceptible to reinfection.Thus, treatment which immediately sterilizes the infection should, if possible,be avoided. This can be difficult when faced with severe cases when delayed treatment means death of the animal. In such cases, preventive treatment of the rest of herd should be considered.

Supportive treatment is advisable. This may include the use of non-steroidal anti-inflammatory drugs, multivitamins, fluid replacement and in some cases, blood transfusions.

Luo: Pound 2 handfuls each of murembe (Erythrina abyssinica) roots and olanga langwe roots. Boil in 5 litres of water for 45 minutes. Allow to cool, and drench 0.5 litres twice a day until the animal recovers. Give half this amount to goats and sheep.

Samburu: Soak 1kg of bark of Ijakwai (Acacia exocephaleia) in 3 litres of water for 12 hours. Drench sick cattle with 1 Tree Top bottle (700ml) of the liquid once. Repeat as required the next day.

Kikuyu: Grind dry bark of muiru (Prunus africana) to powder and mix with 1 litre of water. Drench. Repeat once a day for 2 days.