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Babesiosis/Redwater



Babesiosis/Redwater : Author Rebecca Froelich

Introduction

“Red water” or Babesiosis is a disease caused by Babesia spp. a protozoan parasite (apicompelxa) which infects erythrocytes. Babesia spp. can affect a wide range of wild and domestic mammals including people and is reported nearly worldwide; however, the major economic impact of the disease appears in the cattle industry. While worldwide there are several Babesia species important and pathogenic in animals, only Babesia divergens appears to play a role in the occurrence of “Red Water” in Ireland to date.    
Babesiosis is a “tick-borne disease”. The main vector for Babesia in Europe and on the island of Ireland is considered to be the castor bean tick, Ixodes ricinus. In contrast to Anaplasma sp. infections, there is no evidence of transmission via other biting insects or contaminated instruments (e.g. needles).           
In general, the susceptibility of cattle breeds to ticks and Babesia infections varies; Bos indicus breeds (e.g. Zebu/ Brahman cattle) cattle have been reported to be more resistant to ticks and the effects of Babesiosis infection than Bos Taurus–derived breeds (typical European beef and dairy cattle). Calves younger than 9 months show some age resistance to clinical disease partially due to maternal antibodies; however, due to “inverse age resistance” they are not immune to infection and can so develop their own immunity. Yet, animals which are older than 6 to 9 months are highly susceptible to infection and serious illness if they are introduced from a non-endemic area into an endemic area. Furthermore, animals which survived the disease are usually immune for their commercial life.          

Clinical Signs

The severity of the clinical disease observed depends on the strain and species transmitted. Most clinical signs of babesiosis relate directly to the caused erythrocyte destruction by emerging parasites. In mild cases fever, anorexia, anaemia, muscle tremors, tachypnoea and tachycardia can be observed. In severe case extensive erythrocyte destruction is present causing marked anaemia, jaundice, severe dehydration, (“pipe stem”) diarrhoea and haemoglobinuria (hence “red water”). Late term abortions and temporary infertility in bulls have been reported. Moreover, babesiosis results in metabolic disease more complex than merely the effects of intravascular haemolysis. Death is at least partly due to circulatory shock but also anoxia. A fatality rate of 10% in cases of babesiosis has been reported in the past for Ireland. 

Diagnosis

The diagnosis is usually achieved by the occurrence of clinical symptoms especially haemoglobinuria, epidemiology and the examination of blood smears in which Babesia sp can be detected microscopically within the erythrocytes. On necropsy the diagnosis can be supported by PCR technique. For diagnosis in DAFM laboratories a fresh EDTA blood sample is required.

 

Treatment and Control

There are two equally important factors in controlling the occurrence of babesiosis. Firstly, tick control on affected pastures is needed. This can be achieved by good pasture management with reduction of tick habitats (Rushes, gorse, bracken). Additionally, acaricidal treatment of cattle is recommended using e.g. pyrethroid pour-ons protect cattle for 2-3 weeks depending on the product. Secondly, chemoprophylaxis of susceptible cattle in affected areas is recommended. Imidocarb diproprionate provides protection from clinical disease for up to 4 weeks, but allows concurrently development of immunity if the host is guaranteed to be infected. Dosage is crucial with this product as too high doses eliminate the parasite too quickly and immunity cannot develop (please refer to manufacturers advice on dosing schemes). Note should be taken of the extensive withdrawal period of 213 days for meat and 21 days for milk. A live vaccine had been developed in the past, but is currently not available. Despite best efforts in grassland management, tick control and chemoprophylaxis, clinical cases of babesiosis can still occur and expert stockmanship and vigilance (at least daily observation) in tick season are needed.

While over the last 20 years a decline in the incidence of babesiosis to 0.06% in 2013 has been noted in Ireland, PVPs and farmers should to stay vigilant.  
There is a small number of records reporting B divergens infections in humans in the whole of Europe to date. However, these infections are extremely rare, but potentially life threatening.

 

Zintl, A., McGrath, G., O’Grady, L., Fanning, J., Downing, K., Roche, D., ... & Gray, J. S. (2014). Changing incidence of bovine babesiosis in Ireland. Irish veterinary journal, 67(1), 19.     
Ir Vet J. 2014 Sep 5;67(1):19. doi: 10.1186/2046-0481-67-19. eCollection 2014.

Jubb, K. V. F. (2007). Pathology of domestic animals 5E (Vol. 3). Saunders Elsevier.

Gray, J. S., & Harte, L. N. (1985). AN ESTIMATION OF THE PREVALENCE AND ECONOMIC IMPORTANCE OF CLINICAL BOVINE BABESIOSIS IN THE REPUBLIC-OF-IRELAND. Irish Veterinary Journal, 39(5), 75-78.

http://animalhealthireland.ie/ckfinder/userfiles/files/20130806%20PC%20Redwater.pdf

Species: Bovine
9:07 AM on Thu, 2 August