BOVINE BABESIOSIS. Aetiology Epidemiology Diagnosis Prevention and Control References

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1 AETIOLOGY BOVINE BABESIOSIS Aetilgy Epidemilgy Diagnsis Preventin and Cntrl References Classificatin f the causative agent Bvine babesisis (BB) is a tick-brne disease f cattle caused by the prtzan parasites f the genus Babesia, rder Pirplasmida, phylum Apicmplexa. The principal species f Babesia that cause BB are: Babesia bvis, Babesia bigemina and Babesia divergens. Other Babesia that can infect cattle include B. majr, B. vata, B. ccultans and B. jakimvi. Resistance t physical and chemical actin This agent des nt survive utside its hsts and can nly be transmitted thrugh a tick vectr. Therefre, parameters assciated with resistance t physical and chemical actins (such as temperature, chemical/disinfectants, and envirnmental survival) are nt meaningful. Susceptibility t medicines and vaccines are described under Preventin and cntrl. EPIDEMIOLOGY All Babesia are transmitted by ticks with a limited hst range. The principal vectrs f B. bvis and B. bigemina are Rhipicephalus spp. ticks and these are widespread in trpical and subtrpical cuntries. The majr arthrpd vectr f B. divergens is Ixdes ricinus. BB is principally maintained by subclinically infected cattle that have recvered frm disease. Mrbidity and mrtality vary greatly and are influenced by prevailing treatments emplyed in an area, previus expsure t a species/strain f parasite, and vaccinatin status. In endemic areas, cattle becme infected at a yung age and develp a lng-term immunity. Hwever, utbreaks can ccur in these endemic areas if expsure t ticks by yung animals is interrupted r immun-naïve cattle are intrduced. The intrductin f Babesia infected ticks int previusly tick-free areas may als lead t utbreaks f disease. Hsts B. bvis and B. bigemina cattle water buffal (Bubalus bubalis) and African buffal (Syncerus caffer) reprts f disease in white-tailed deer (Odcileus virginianus) in Mexic B. divergens cattle and reindeer (Rangifer tarandus) Mnglian gerbils (Merines unguiculatus); ther peridmestic rdents are resistant t disease Splenectmised humans and nn-human primates are highly susceptible Experimental infectin with n clinical signs have been dcumented in splenectmised ungulates including mufln (Ovis musimn), red deer (Cervus elaphus), re deer (Caprelus caprelus), and fallw deer (Dama dama) Life Cycle and Transmissin BB is principally transmitted by means f ticks Tick vectrs f Babesia bigemina: Rhipicephalus micrplus (frmerly Bphilus micrplus) and Rhipicephalus annulatus (frmerly Bphilus annulatus); Rhipicephalus declratus, Rhipicephalus geigyi, and Rhipicephalus evertsi are als cmpetent vectrs B. bigemina transmitted by feeding f adult and nymphal stages f ne-hst Rhipicephalus spp. ticks Tick vectrs f Babesia bvis: Rhipicephalus micrplus and Rhipicephalus annulatus; Rhipicephalus geigyi is als a cmpetent vectr B. bvis transmitted by feeding f larval stages f ne-hst Rhipicephalus spp. ticks 1

2 Tick vectrs f Babesia divergens: principal vectr is Ixdes ricinus Ixdes ricinus is a three-hst tick with nly adult stages feeding n vertebrates (eg. cattle) Babesia sprzites are inculated int the vertebrate hst by ticks and invade red bld cells (RBCs) where they transfrm int trphzites These grw and divide int tw rund, val r pear-shaped merzites which, in turn, are capable f infecting new RBCs; the divisin prcess is then repeated Babesia parasites can be transmitted transvarially between tick generatins; in the case f Ixdes, surviving up t 4 years withut a vertebrate hst Babesia may als be transmitted by fmites and mechanical vectrs cntaminated by infected bld Infrequently, calves can becme infected in uter Surces f infectin Bld infected with Babesia parasites and assciated vectrs f infected bld (especially ticks, but als by mechanical means) Occurrence BB is fund in areas where its arthrpd vectr is distributed, especially trpical and subtrpical climates. Babesia bvis and B. bigemina are mre widely distributed and f majr imprtance in Africa, Asia, Australia, and Central and Suth America. Babesia divergens is ecnmically imprtant in sme parts f Eurpe and pssibly nrthern Africa. Fr mre recent, detailed infrmatin n the ccurrence f this disease wrldwide, see the OIE Wrld Animal Health Infrmatin Database (WAHID) Interface [ r refer t the latest issues f the Wrld Animal Health and the OIE Bulletin. DIAGNOSIS Incubatin perid is ften 2 3 weeks r lnger after tick infestatin. Shrter incubatin perids have hwever been dcumented in the field and thrugh experimental inculatin (4 5 days fr B. bigemina and days fr B. bvis). Clinical diagnsis Clinical manifestatins f disease assciated with BB are typical f a haemlytic anaemia disease prcess but vary accrding t agent (i.e. species f parasite) and hst factrs (i.e. age, immune status). BB is predminantly bserved in adult cattle with B. bvis generally being mre pathgenic than B. bigemina r B. divergens. Infected animals develp a life-lng immunity against re-infectin with the same species and sme crss-prtectin is evident in B. bigemina-immune animals against subsequent B. bvis infectins. Babesia bvis High fever Ataxia and incrdinatin Anrexia Prductin f dark red r brwn-clred urine Signs f general circulatry shck Smetimes nervus signs assciated with sequestratin f infected erythrcytes in cerebral capillaries In acute cases: maximum parasitaemia (percentage f infected erythrcytes) in circulating bld is ften less than 1% Babesia bigemina Fever Haemglbinuria and anaemia 2

3 Prductin f dark red r brwn-clred urine Nervus signs minimal r nn-existent as intravascular sequestratin f infected erythrcytes des nt ccur Parasitaemia ften exceeds 10% and may be as high as 30% Babesia divergens Parasitaemia and clinical appearance are similar t B. bigemina infectins Lesins Lesins bserved are thse mst ften assciated with an intravascular haemlytic cnditin Pale r icteric mucus membranes; bld may appear thin and watery Subcutaneus tissues, abdminal fat and mentum may appear icteric Swllen liver with an range-brwn r paler clratin; enlarged gall bladder cntaining thick, granular bile Enlarged, dark, friable spleen Kidneys appear darker than nrmal with pssible petechial haemrrhages Bladder may cntain dark red r brwn-clred urine Pssible edema f lungs Petechiae r ecchymses n surface f heart and brain Differential diagnsis Anaplasmsis Trypansmiasis Theilerisis Bacillary haemglbinuria Leptspirsis Eperythrznsis Rapeseed pisning Chrnic cpper pisning Labratry diagnsis Samples Several thick and thin bld smears cllected frm superficial skin capillaries (e.g. tip f the ear r tip f the tail) f live animals during the acute phase f the disease (appearance f fever) thin bld films shuld be air-dried, fixed in abslute methanl fr 1 minute and stained in 10% Giemsa stain fr minutes bld films shuld be stained as sn as pssible after preparatin t ensure prper stain definitin thick films are made by placing a small drp (apprximately 50 µl) f bld n t a clean glass slide. The drplet is air-dried, heat-fixed at 80 C fr 5 minutes, and stained (withut fixing in methanl) in 10% Giemsa fr 15 minutes unstained bld smears shuld nt be stred with r near frmalin slutins as it may affect staining quality If it is nt pssible t make fresh smears frm capillary bld, sterile jugular bld shuld be cllected int an anticagulant such as ethylene diamine tetra-acetic acid (EDTA) (e.g. 1 mg/ml); heparin is nt recmmended as it may affect staining The sample shuld be kept cl, preferably at 5 C, until delivery t the labratry, bld films shuld be made and stained preferably within 2 3 hurs f cllectin B. bvis is sequestered and fund in higher numbers in capillary bld, B. bigemina and B. divergens parasites are unifrmly distributed thrugh the vasculature Samples frm dead animals shuld cnsist f thin bld films, as well as smears frm rgans Organ smears acquired at necrpsy (in rder f preference): cerebral crtex, kidney, liver, spleen and bne marrw rgan smears are made by pressing a clean slide n t a freshly cut surface f the rgan r by crushing a small sample f the tissue between tw clean micrscpe slides drawn lengthwise t leave a film f tissue n each slide 3

4 rgan smear is then air-dried (assisted by gentle warming in humid climates), fixed fr 5 minutes in abslute methanl, and stained fr minutes in 10% Giemsa especially suitable fr the diagnsis f B. bvis infectins but unreliable if sample taken 24 hurs r lnger after death has ccurred Babesia parasites can ften be detected in bld taken frm veins, in the lwer limb regin, ne r mre days after death Serum samples shuld als be cllected Prcedures Identificatin f the agent Micrscpic examinatin f bld traditinal methd f identifying agent in infected animals by micrscpic examinatin f Giemsa-stained thick and thin bld films stained smears are examined under il immersin using (as a minimum) a 8 eyepiece and a 60 bjective lens thick bld films are especially useful fr the diagnsis f lw level B. bvis infectins, as are rgan smears mrphlgy f Babesia described in varius surces, including OIE Manual f Diagnstic Tests and Vaccines fr Terrestrial Animals sensitivity f test can detect parasitaemias as lw as 1 parasite in 10 6 red bld cells in thick bld films Babesia species differentiatin is gd in thin films but pr in the mre sensitive thick films adequate fr detectin f acute infectins, but nt fr detectin f carriers where parasitaemias are very lw parasite identificatin and differentiatin imprved by using a flurescent dye, such as acridine range instead f Giemsa Plymerase chain reactin (PCR) assays - very sensitive particularly in detecting B. bvis and B. bigemina in carrier cattle a PCR-enzyme-linked immunsrbent assay (ELISA) is reprted t be at least 1000 times mre sensitive than thin bld smears fr detectin f B. bvis a number f PCR techniques have been described that can detect and differentiate species f Babesia in carrier infectins current PCR assays generally d nt lend themselves well t large-scale testing; unlikely t supplant serlgical tests as the methd f chice fr epidemilgical studies PCR assays are useful as cnfirmatry tests and in sme cases fr regulatry testing In-vitr culture methds used t demnstrate presence f carrier infectins f Babesia spp.; B. bvis has als been clned in culture minimum parasitaemia detectable by this methd depends n the facilities available and the skills f the peratr but culd be as lw as 10 10, making it a very sensitive methd fr the demnstratin f infectin methd is 100% specific Animal inculatin is nt suitable fr diagnstic purpses Serlgical tests Babesia bvis enzyme-linked immunsrbent assay ELISA fr diagnsis f B. bvis infectin uses a whle merzite antigen; undergne extensive evaluatin Cmpetitive ELISAs using recmbinant merzite surface and rhptry assciated antigens f B. bvis have recently been develped; nt yet been widely validated Babesia bigemina enzyme-linked immunsrbent assay a cmpetitive ELISA develped and validated in Australia is the nly ELISA in rutine use. It has been included in the OIE Manual f Diagnstic Tests and Vaccines fr Terrestrial Animals n ther well-validated ELISA available fr B. bigemina; due in part t the fact that antibdies t B. bigemina typically have pr specificity ELISAs have als been develped fr B. divergens using antigen derived frm culture, Merines r cattle, but nne has been validated internatinally 4

5 Indirect flurescent antibdy (IFA) test widely used t detect antibdies t Babesia spp., but the B. bigemina test has pr specificity crss-reactins with antibdies t B. bvis in the B. bigemina IFA test are a particular prblem in areas where the tw parasites cexist disadvantages f lw sample thrughput and subjectivity Cmplement fixatin has been used t detect antibdies against B. bvis and B. bigemina used t qualify animals fr imprtatin int sme cuntries Other tests: dt ELISA, slide ELISA, and latex and card agglutinatin tests tests shw acceptable levels f sensitivity and specificity fr B. bvis and, in the case f the dt ELISA, als fr B. bigemina hwever, nne f these tests appears t have been adpted fr rutine diagnstic use in labratries ther than thse in which the riginal develpment and validatin tk place adaptability f these tests t rutine diagnstic labratries is therefre unknwn Fr mre detailed infrmatin regarding labratry diagnstic methdlgies, please refer t Chapter Bvine babesisis in the latest editin f the OIE Manual f Diagnstic Tests and Vaccines fr Terrestrial Animals under the heading Diagnstic Techniques. PREVENTION AND CONTROL Sanitary prphylaxis Eradicatin f BB has been accmplished by eliminatin f tick vectr in areas where eradicatin f tick is nt feasible r desirable, ticks are cntrlled by repellents and acaricides Reducing expsure f cattle t ticks repellents, acaricides and regular inspectin; animals and premises cntrl and eradicatin f the tick vectr Cattle develp a durable, lng-lasting immunity after a single infectin with B. bvis, B. divergens r B. bigemina, a feature that has been explited in sme cuntries t immunise cattle against babesisis Endemic envirnments shuld be mnitred carefully intrductin f immun-naïve animals intrductin f new species r strains f disease agent interruptins in expsure t ticks and disease due t changes in climate, hst factrs and management Special care in pssible mechanical infectin f hrses with cntaminated bld Medical prphylaxis Vaccine fr Babesia: Live vaccine: mst live vaccines cntain specially selected strains f Babesia (mainly B. bvis and B. bigemina) and are prduced in calves r in vitr in gvernment-supprted prductin facilities as a service t the livestck industries cautin shuld be used in their emplyment as they may be virulent in adult animals, may be cntaminated with ther disease agents and culd lead t hypersensitivity reactins; usually used in yunger animals an experimental B. divergens vaccine prepared frm the bld f infected Merines has als been used successfully Killed vaccine: prepared frm bld f B. divergens-infected calves; little infrmatin available n level and duratin f the cnferred immunity Other vaccines: parasite prteins have been characterised but n effective subunit vaccine is available cmmercially experimental vaccines cntaining antigens prduced in vitr have been develped but the level and duratin f prtectin against heterlgus challenge are unclear 5

6 Fr mre detailed infrmatin regarding vaccines, please refer t Chapter Bvine babesisis in the latest editin f the OIE Manual f Diagnstic Tests and Vaccines fr Terrestrial Animals under the heading Requirements fr Vaccines and Diagnstic Bilgicals. Endemic areas Clinically affected animals treated with an antiparasitic drug (diminazene diaceturate, imidcarb, amicarbalide); efficacy depends n timely detectin early in disease Babesia parasites can be cleared frm carrier animals; reduces clinical signs Imidcarb has been reprted t prtect animals frm disease but allw develpment f immunity; cautin in regard t residues in milk and meat Cnsideratin can be given t bld transfusins and ther supprtive therapy, if apprpriate Fr mre detailed infrmatin regarding safe internatinal trade in terrestrial animals and their prducts, please refer t the latest editin f the OIE Terrestrial Animal Health Cde. REFERENCES AND OTHER INFORMATION Brwn C. & Trres A., Eds. (2008). - USAHA Freign Animal Diseases, Seventh Editin. Cmmittee f Freign and Emerging Diseases f the US Animal Health Assciatin. Bca Publicatins Grup, Inc. Cetzer J.A.W. & Tustin R.C. Eds. (2004). - Infectius Diseases f Livestck, 2nd Editin. Oxfrd University Press. Hmer M.J. & et al. (2000) - Clin. Micrbil. Rev., 13 (3): 451. Kahn C.M., Ed. (2005). - Merck Veterinary Manual. Merck & C. Inc. and Merial Ltd. Spickler A.R., & Rth J.A. Iwa State University, Cllege f Veterinary Medicine - Wrld Organisatin fr Animal Health (2009). - Terrestrial Animal Health Cde. OIE, Paris. Wrld Organisatin fr Animal Health (2008). - Manual f Diagnstic Tests and Vaccines fr Terrestrial Animals. OIE, Paris. * * * The OIE will peridically update the OIE Technical Disease Cards. Please send relevant new references and prpsed mdificatins t the OIE Scientific and Technical Department (scientific.dept@ie.int). Last updated Octber

5.1. What do we need to know before we start planning a canine rabies control programme?

5.1. What do we need to know before we start planning a canine rabies control programme? 5.1. What d we need t knw befre we start planning a canine rabies cntrl prgramme? Yu need t knw abut: The epidemilgy f rabies in yur area The reservir species in yur area Hw rabies is transmitted. This