This article is part of a series of informative animal health articles. The series goes hand in hand with the #VideoVet video series – watch the video below.
Redwater is a disease commonly found in cattle. It is caused by the protozoan parasite Babesia and is transmitted via a tick vector. The parasite infects and destroys the red blood cells of animals, with the excretion of red or blackish urine a common characteristic. There are two types of redwater. African redwater is caused by Babesia bigemina and is transmitted by three tick species: Rhipicephalus decoloratus (African blue tick), Rhipicephalus microplus (Asiatic blue tick) and Rhipicephalus evertsi evertsi (red-legged tick). Asiatic redwater is caused by Babesia bovis and is transmitted only by Rhipicephalus microplus (Asiatic blue tick).
As African and Asiatic redwater differs remarkedly in clinical signs, we will discuss each disease individually. African redwater is characterised by the red to black discolouration of urine (haemoglobinuria), together with fever, anorexia, anaemia and depression. Constipation may also be seen. The disease takes 7-14 days after transmission of the Babesia parasite to be symptomatic. Asiatic redwater on the other hand is very acute and fatal. Cattle will show nervous signs such as disorientation, circular walking movements and a paddling gait. The incubation period varies between 14 and 25 days.
Asiatic redwater is transmitted during the larval stage (and very seldom the nymph stage) of Rhipicephalus microplus. In the case of African redwater, the nymph and adult stage transmits the infection. This is significant because by the time you see the adult ticks on the animals, they have already been infected with the Babesia parasite even though they might only appear sick two weeks later.
Treating the disease
Diminazene (Berenil® R.T.U.) and imidocarb (Imizol) are two drug groups available for the treatment of redwater. Berenil® R.T.U. prevents and cures redwater in cattle. It also prevents Asiatic and African redwater infection in cattle for two and four weeks, respectively. Imizol kills the organisms responsible for redwater (babesiosis) and tick-borne gallsickness (anaplasmosis) in cattle. It also guards against infection with Asiatic and African redwater for up to four and eight weeks, respectively. Sometimes the disease has progressed to such an extent, that a blood transfusion might be necessary. Multivitamins or vitamin B complex formulations can also be given but there is little scientific evidence to substantiate its efficacy.
Handling an outbreak
It is imperative to immediately quarantine and treat animals showing symptoms. Diminazene (Berenil® R.T.U.) is recommend as a first line of defence. To minimise the spread of infection, it is crucial to dip all animals immediately to remove all stages of ticks present on the animals. Animals that do not appear sick or affected should be monitored for signs of infection by taking their temperature at least once a day for two to three weeks. If this is not possible, the entire herd must be blocked with the full recommended dose of diminazene (Berenil® R.T.U.) as soon as possible. Animals with Asiatic redwater rarely respond to treatment and will die even after receiving treatment. If there is an Asiatic redwater outbreak in the herd, all non-symptomatic animals must be blocked immediately with the full dose of imidocarb to lessen any further losses.
Infection and immunity
Calves have an innate (born with it) immunity between two and nine months of age, irrespective of the dam’s immunity. Infection in this period will ensure that immunity is maintained. If no infection occurs, it can lead to increased susceptibility. Older animals maintain their immunity by continuous challenges from infected ticks. Immunity persists long term; however, conditions such as cachexia and severe stress can cause the immunity to lapse with animals subsequently developing disease.
Reg. No. G2702 (Act 36/1947)
Namibia Reg. No. V00/17.4.2/638 NS0
Contains: Diminazene 0,07 g/ml, Phenazone 0,375 g/ml. Indications: Berenil® R.T.U. cures and prevents redwater in cattle and cures biliary fever in dogs and horses. Prevents Asiatic (European) redwater for 2 weeks and African redwater for 4 weeks. Dose: Cattle:0,5 ml per 10 kg live weight preferably by deep intramuscular injection. Pack size: 20 ml & 100 ml.