Contents lists available atScienceDirect
Veterinary
Parasitology
j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / v e t p a r
Research
paper
Population
genetic
analysis
of
Theileria
parva
isolated
in
cattle
and
buffaloes
in
Tanzania
using
minisatellite
and
microsatellite
markers
Elpidius
Rukambile
a,∗,
Eunice
Machuka
b,
Moses
Njahira
b,
Martina
Kyalo
b,
Robert
Skilton
b,
Elisa
Mwega
c,
Andrew
Chota
a,
Mkama
Mathias
a,
Raphael
Sallu
a,
Diaeldin
Salih
daTanzaniaVeterinaryLaboratoryAgency(TVLA),P.O.Box9254,DaresSalaam,Tanzania
bBiosciencesEasternandCentralAfrica—InternationalLivestockResearchInstituteHub(BecA-ILRIHub),P.O.Box30709-00100,Nairobi,Kenya cFacultyofVeterinaryMedicine,GenomeScienceCenter,SokoineUniversityofAgriculture(SUA),P.O.Box3019,Morogoro,Tanzania dVeterinaryResearchInstitute(VRI),P.O.Box8067,Khartoum,Sudan
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received18December2015 Receivedinrevisedform22April2016 Accepted24April2016
Keywords: Buffalo Cattle Diversity Populationgenetic Tanzania Theileriaparva
a
b
s
t
r
a
c
t
ApopulationgeneticstudyofTheileriaparvawasconductedon103cattleand30buffaloisolatesfrom Kibaha,Lushoto,NjombeDistrictsandselectedNationalparksinTanzania.Bovinebloodsampleswere collectedfromthesestudyareasandcategorizedinto5populations;Buffalo,Cattlewhichgrazecloseto buffalo,Kibaha,LushotoandNjombe.SamplesweretestedbynestedPCRforT.parvaDNAandpositives werecomparedforgeneticdiversitytotheT.parvaMugugavaccinereferencestrain,using3microand 11minisatellitemarkersselectedfromall4chromosomesoftheparasitegenome.Thediversityacross populationswasdeterminedbythemeannumberofdifferentalleles,meannumberofeffective alle-les,meannumberofprivatealleleandexpectedheterozygosity.Themeannumberofalleleuniqueto populationsforCattleclosetobuffalo,Muguga,Njombe,Kibaha,LushotoandBuffalopopulationswere 0.18,0.24,0.63,0.71,1.63and3.37,respectively.Themeannumberofdifferentallelesrangedfrom6.97 (Buffalo)to0.07(Muguga).Meannumberofeffectiveallelesrangedfrom4.49(Buffalo)to0.29(Muguga). Themeanexpectedheterozygositywere0.070.29,0.45,0.48,0.59and0.64forMuguga,cattlecloseto buffalo,Kibaha,Njombe,LushotoandBuffalopopulations,respectively.TheBuffaloandLushotoisolates possessedaclosedegreeofdiversityintermsofmeannumberofdifferentalleles,effectivealleles, pri-vateallelesandexpectedheterozygosity.Thestudyrevealedmorediversityinbuffaloisolatesandfurther studiesarerecommendedtoestablishifthereissharingofparasitesbetweencattleandbuffaloeswhich mayaffecttheeffectivenessofthecontrolmethodscurrentlyinuse.
©2016ElsevierB.V.Allrightsreserved.
1. Introduction
TheileriosisintheformofEastCoastfever(ECF)isavery dev-astatingtick-bornediseaseofcattlewhich ishighlyendemic in 11countriesintheEastern,Central andSouthern Africa(ECSA) regionwhereitisamajorhindrancetocattleproduction(Mukhebi etal.,1992).EastCoastfeveriscausedbythetick-borne haemo-protozoanparasiteTheileriaparvatransmittedbybrowneartick,
Rhipicephalusappendiculatus.EconomiclossesresultingfromECF
∗Correspondingauthor.
E-mailaddresses:rukambile@yahoo.com(E.Rukambile),enidm32@gmail.com (E.Machuka),wanjahira@gmail.com(M.Njahira),M.Kyalo@cgiar.org(M.Kyalo), rskilton@icipe.org(R.Skilton),elisamwega@yahoo.co.uk(E.Mwega), chotaandrew@gmail.com(A.Chota),matsonics2000@yahoo.co.uk(M.Mathias), raphaelsallu@yahoo.com(R.Sallu),diaeldin2000@hotmail.com(D.Salih).
areattributedtohighmorbidityandmortalityinlocalandexotic cattleandreducedmilkproductioninlactatingcows(Mbwambo
etal.,2002;Kivariaetal.,2007).
T.parvainfectioninsusceptible cattleresultsinarapid pro-liferationofinfectedlymphocytesanddeathwithintwotothree weeksifnotreatmentiscommenced(IrvinandMwamachi,1983). Duringthecourseofinfection,lymphocytesandantigen present-ingmacrophagesoftheMphilineagearetransformed,resultingin alossofphenotypicmarkersandconsequently,alossoffunction
(Morrison,2009;Jeongetal.,2009).InTanzaniacontrolofT.parva
involvesapplicationofacaricidesonceortwiceperweektocontrol thevector,useofcommerciallyavailablechemotherapyand immu-nizationofanimalsusinginfectionandtreatmentmethod(ITM). ITMcomprisesinoculationofcattlewithahomogenateofinfected tickssimultaneouslywithasingledoseofalong-actingformulation ofoxy-tetracyclinetocurtailtheinfection.Thisresultsinlongterm immunity againstthe homologousparasite strainsbut variable
protectionagainst challengewith heterologous parasite strains
(Irvinetal.,1983).PopulationgeneticstudiesofT.parvaare
impor-tanttodeterminethegeneticexchangeamongtheparasiteisolates. Thelevelsofrecombinationamongparasitesdeterminetheextent ofgeneralpopulationdiversitywhichhavegreatimplicationinthe successand/orfailureofITM(Katzeretal.,2006;McKeever,2007;
KuoandKissinger,2008;Katzeretal.,2010).Recombinationunder
selectioncansupportrapiddisseminationofanallelewithina pop-ulation.InTheileriaspp.,recombinationcanplayanimportantrole ingeneratingdiversityatlocithatarerelevantformanipulating hostimmunityduringevasion(Katzeretal.,2011).
Miniand microsatelliteshave highrates ofmutation dueto replicationslippageandrepair.Thehighratesofmutationresult inhighlevelsofpolymorphism atthevariable numbertandem repeat(VNTR)locimakingthemidealmarkersforpathogen diver-sitystudy(Ouraetal.,2003).Miniandmicrosatelliteshavebeen successfullyusedtodeterminepopulationdiversityofT.parvain differentstudies.Miniand microsatellitemarkerswereusedto characterizethethreestrainswhicharepresentascomponents oftheMugugaT.parvavaccinecocktail,todeterminetheabilityof eachcomponenttoinducecarrierstate(Ouraetal.,2004)andthe possibilityofbeingtransmittedfromvaccinatedanimalstoother susceptibleanimals(Ouraetal.,2007).Fourminiand microsatel-litemarkerswereusedtostudydiversityofthethreestockswhich arethecomponentsoftheMugugacocktailvaccinewhereby14 differentgenotypeswererevealed(Pateletal.,2011).Ontheother hand,9minisatelliteswereusedtostudypopulationgeneticsand sub-structureofT.parvapopulationinthesamplescollectedfrom twodistrictsinZambiawithsuccess(Muleyaetal.,2012).The cur-rentstudyfocusedonthepopulationstructureofT.parvaisolated fromcattleintwodistrictsintheEasternzoneandonedistrictinthe SouthernhighlandzoneandbuffaloesfromselectedNationalParks ofTanzaniausing11miniand3microsatellitemarkers. Determi-nationofparasitediversityinbuffaloisequallyimportantbecause thebuffalo-derivedparasitescanbemaintainedbetweencattleand tickpassageandyettheparasitepopulationinbuffaloisoftenmore diversethanincattle(Bishopetal.,1994;Potgieteretal.,1988;
CollinsandAllsopp,1998;Sibekoetal.,2010).
2. Materialsandmethods
2.1. Studysites
Thestudywascarried outin 3 districtsnamely, Kibaha and LushotointheEasternandNjombeintheSouthernHighland agro-ecologicalzonesofTanzania.KibahaandNjombeare675kmapart, Kibaha andLushotoare419km apart,Lushotoand Njombeare 847kmapart.EastCoastfeverhasbeenmorefrequentlyreported inKibahadistrictandimmunizationhasbeenpracticed.Previously therewerefewerreportsofthediseaseinNjombeand Lushoto highlandsbutinrecenttimes,ECFcaseshavebeenreportedand thevectors arefrequently seen (Personalcommunications). No vaccinationhadbeenreportedinthesiteswheresamplingwas con-ductedinNjombeandLushotoandthecattlesampledatKibaha, LushotoandNjombehadnohistoryofco-grazingwithbuffaloes. Ruahaand Mikumi National parks are along theroad towards Njombeandtheyareabout247kmapart,theclosestNationalpark toNjombebeingRuahawhichis161kmfromNjombe.Mkomazi NationalParkislocatedintheNorthEasternTanzania(Fig.1)
2.2. Bloodsampling
Atotalof150bloodsampleswererandomlycollectedfrom cat-tlewhich havenohistoryofco-grazingwithbuffaloinNjombe, Kibaha and Lushotodistricts, 50 blood samplesbeing collected
Fig.1.AMapofTanzaniashowingsamplingareas.
Table1
Locationsandhostswherethesampleswerecollectfrom.
Location Numberofsample Host
fromeachdistrict.Tenmillimeterofbloodsamplefromeach ani-malwascollectedinEDTA Vacutainertubes (BectonDickinson, Oxford,UK)throughjugularveinpuncture,keptincoolboxand laterwerefrozenat−20◦CatCentralVeterinaryLaboratory,Dar
EsSalaam,Tanzania.Thebloodsamplesfrombuffaloandthe cat-tlesharingpasturewithbuffalowereobtainedfromthesample archiveatCentreforInfectiousdiseaseandBiotechnology,DarEs Salaam,Tanzania(Table1).
2.3. ScreeningforT.parvapositivesamples
DNA was extracted from thawed blood using a commer-cial extractionkit according tothe manufacturer’s instructions (PureLink® GenomicDNAMiniKit,Invitrogen,USA).Allsamples
werescreenedforT.parvausinganestedpolymerasechain reac-tion(PCR)assaytargetingthe104kDaantigen(p104)gene(Skilton etal.,2002).TheassaywasrunintwoPCRrounds;theprimaryand secondaryPCR;usingouterprimersforprimaryPCR(For15′-ATT
TAAGGAACCTGACGTGACTGC-3′andRev15′-TAAGATGCCGAC
TATTAATGACACC-3′),andinnerprimersforsecondary(nested)
PCR(For25-GGCCAAGGTCTCCTTCAGAATACG-3andRev25′-TGG
GTGTGTTTCCTCGTCATCTGC-3′).Primersweredesignedbased
onp104antigenicgene(GenebankM29954).Inboth,primaryand secondaryPCR,BioneerAccuPower®PCRPre-mixes(Seoul,South
Korea)wasused.TheprimaryPCRcomposedof17lnucleasefree
water,10pmoleofeachoftheprimers(ForandRev)and2lof
gDNAat 20ng/ltohavea final volumeof 20l.Thereaction
Table2
PanelofminiandmicrosatellitemarkersusedtogenotypeT.parvasamplesusedinthisstudywiththeirrespectivechromosomes,outernestedprimers(Ouraetal.,2003) andinnernestedprimers(Salihetal.unpublisheddata).
Outernestedprimers Innernestedprimers
Chromosome Name Sequence Name Sequence
1 ms2ForO aagttagtatcaccaccaggctgg ms2ForN gcccaatgtaccgagaatcctcac ms2RevO ggctcatctaccactccaactcc ms2RevN attctccgcattctccaccacctc 1 ms5ForO aacacagtaactaacccaggcc ms5ForN aatcttccaatcccaaccacatac
ms5RevO aactccagcggaatcccgaaata ms5RevN cccgaaataaaaccaaattccacc 2 ms7ForO tgggtagagattggaatacgcgag ms7ForN ttaacttatctccctctccctccc
ms7RevO aataccgacgcgttccgaggaatc ms7RevN acactctcaacaactcactcttcc 1 MS3ForO cccgatctcactcacatacaacc MS3ForN ccaccgtaaccctctataccat
MS3RevO cagcaaatccaactcgtcgtcctg MS3RevN gacatctccctcaaatcagactc 1 MS7ForO ctcctcagcatcctgctgctcattg MS7ForN gttcagtcctatggcaattcag
MS7RevO gcgcatgactgcttttacattaaccc MS7RevN caaacctcttcaaattcactctagg 1 MS8ForO ggcgtgacggtaatacaccttcc MS8ForN gcctcctcaagcaattcagta
MS8RevO cctcctagacactcccgaagatg MS8RevN ctggttcaaacacatcaaggtaca 2 MS16ForO catggcattcctaggcatcacatc MS16ForN cctcctccatactactaacctacc
MS16RevO ccaagggaattaatactgttggag MS16RevN cagcgctcagattcacttgtact 2 MS19ForO ccgcgtacagactaaactcgccg MS19ForN ccagacacctcaaatcccaagta
MS19RevO cctccaactgatccaccctcgcag MS19RevN ccacactgccacctaatacaaa 3 MS21ForO gatgagcacaaggagttcctggtg MS21ForN ttctacccaacgccactctatgcg
MS21RevO gacggcgtctgagatggcgatgac MS21RevN tgactcccgtcttatccaaattcg 3 MS25ForO ccagagatctcggacacaactcc MS25ForN acacacccatcaacgtagtaac
MS25RevO taaggtgccaaacggcggacac MS25RevN caccatcacactcttaaccat 3 MS27ForO ccgccacctcagtctcgaga MS27ForN cctgcgatacatttctaatcc MS27RevO cacaactcacaccggaatctcac MS27RevN gtaataccattcccacctctac 4 MS33ForO ctcattaccactctacccatcgc MS33ForN cttctcaaggtaccgtaaacc MS33RevO catggtccatcttcatctggtcc MS33RevN cctcactactccaatagttcttc 4 MS34ForO gtgcctagagagggaacggatatg MS34ForN gattacgccactgtcataaccacc
MS34RevO cctccggctgagattagtggcagg MS34RevN aacactccacgctccacattcacc 4 MS40ForO cggtggaggctcggatgtgtgc MS40ForN catatcacctcatggtacacac
MS40RevO gcaggatcaacatcgccaaccac MS40RevN ccagccctaatacacaaatc ms—Microsatellite.
MS—Minisatellite.
ForO—Forwardouternestedprimer. RevO—Reverseouternestedprimer. ForN—Forwardinnernestedprimer. RevN—Reverseinnernestedprimer.
control.TheamplificationconditionsforprimaryPCRwere94◦C
for1minfollowedby35cyclesof94◦Cfor1min,60◦Cfor1min,
72◦Cfor1minwithadditional10minat72◦Casfinalextension.
ThecomponentsofthesecondaryPCRremainedthesameasforthe primaryPCRexceptthetemplatewhichwasprimaryPCRproducts dilutedat1:10.Theamplificationconditionswerethesameexcept theannealingtemperatureandthenumberofcycleswasreduced to55◦Cand30cycles,respectively.Allamplificationsweredone
usingaprogrammablethermalcycler(MJResearch,Watertown, MA,USA).ThesecondaryroundPCRproductswereanalyzedby electrophoresisrunat100Vfor40minin2%agarosegelstained withGelRed(BiotiumInc.USA).
2.4. PCRamplificationandanalysisofminiandmicrosatelliteloci
ThenestedPCRdeployingtheouterandinnerprimersdesigned
byOuraetal.(2003)andSalihetal.(unpublisheddata)
respec-tively(Table2)wasperformedtoamplifyeachof11miniand3 microsatellitesusedinthestudyforeachsamplethatwas posi-tivebyp104nestedPCRamplification.Theinnerforwardprimer ofeachmarkerwasfluorescentlylabeledatthe5′ endwithone
ofthefollowingfourstandarddyes;6-FAM(Blue),NED(Yellow), PET(Red)andVIC(Green)(Bioneer,Korea),toenabledetectionon anABIgeneticanalyser.TheprimaryPCRamplificationwasdone in10lcomprising of2lof 20ng/lgenomicDNA,0.08lof
0.5U/lDreamTaqpolymerase(ThermoScientific,Lithuania,EU),
0.2lof10mMdNTPs,0.4lofeachouterprimersat10pmoleand
1lof10XDreamTaqbufferwith20mMMgCl2(ThermoScientific,
Lithuania,EU).Thenucleasefreewaterwasusedasnegativecontrol andtheDNAsampleknowntobeT.parvapositivefromBecA-ILRI Hubsamplerepositorywasusedaspositivecontrol.Thecycling
conditionsfortheprimaryPCRwereasfollows;Initial denatura-tionat95◦Cfor5minfollowedby35cyclesofdenaturationat94◦C
for30s,annealingat55◦Cfor1min,extensionat72◦Cfor1min
plusafinalextensionat72◦Cfor10min.ForthesecondaryPCR,
allotherreagentsremainedthesameexceptthat0.5lofthe
pri-maryPCRwasusedasthetemplateandthevolumeofwaterwas increasedaccordinglytogiveatotalof10lreactionvolume.The
cyclingconditionsforthesecondaryPCRwereasfollows;Initial denaturationat95◦Cfor5minfollowedby25cyclesof
denatura-tionat94◦Cfor30s,annealingat58◦Cfor1min,extensionat72◦C
for1minplusafinalextensionat72◦Cfor20min.Threemicroliter
oftheampliconswereanalyzedona1.5%agarosegelstainedwith GelRed(BiotiumInc.USA)tocheckforamplificationsuccess.One andhalftotwolof2−4PCRproductsofthesamesample
ampli-fiedbyforwardprimerslabeledwithdifferentdyeswereco-loaded onthesamewellof96wellsplatewith8lmixtureofHiDiand
LIZ500mixedat1mlLIZ500and15lHiDi.Thesamplesonthe
plateweredenatureat95◦Cbythermocyclerfor3min,fastcooled
onice for10minthentheplates wereloadedinanABI3730xl geneticanalyser(Appliedbiosystem)forcapillaryelectrophoresis
(Mwegaetal.,2014;Muleyaetal.,2012).Capillary
electrophore-siswascarriedoutatBioscienceeasternandcentralAfrica(BecA) sequencingandgenotypingunit.DNAfragmentsizeswere ana-lyzedbyLIZ500standardsizemarker(AppliedBiosystems)using GeneMappersoftware(AppliedBiosystems).
2.5. Categoriesofthepopulationusedinstudy
Table3
Majorallelefrequency,genediversity,numberofallelesandpolymorphic informa-tioncontent(PIC)oftheminiandmicrosatellitemarkersusedtocharacterizing5 populationsandMugugaisolateusedinthisstudy.
Marker Majorallelefrequency Numberofallele Genediversity PIC
ms2 0.40 26.00 0.79 0.78
withbuffalo.Samplesfromtheseareasweretreatedasindividual populationsnamedasKibaha,NjombeandLushotopopulations. Samplesfrom buffaloes werecategorized as buffalo population regardlessoftheiroriginandthesamplesfromcattlewhichgraze closeorwithintheareaswherebuffaloesaregrazingwere catego-rizedascattleclosetobuffalopopulation.Mugugavaccinestrain wasalsoincludedinthestudyandwasreferredasMugugaisolate.
2.6. Dataanalysis
ThepowerMarkersoftware(LiuandMuse,2005)wasusedto calculatethediversityparametersofthemarkersusedinthisstudy wherebythemajorallelefrequency,genediversity,numberof alle-lesandpolymorphicinformationcomponent(PIC)ofeachmarker weregenerated.Allelicrichnessasthemeanacrossalllociforeach populationandAnalysisofMolecularvariance(AMOVA)was esti-matedusingGenAlEXsoftwareversion6.5(PeakallandSmouse 2012).The samesoftwarewasusedtocalculate Principle com-ponentanalysis(PCoA).DARwinVersion5software(Perrierand
Jacquemoud-Collet,2006)wasusedtoconstructthedendrogramto
determinetherelationshipamong5populationsusedinthestudy andtheMugugaisolate.
3. Results
3.1. ScreeningforT.parvaandPCRamplificationofminiand microsatellitemarkers
Atotalof105(70%)cattle(Lushoto41,Njombe32,Kibaha23and cattleclosetobuffalo9)and30(49%)buffalosampleswerepositive byp104amplification.Samplespositiveforp104PCRamplification wereamplifiedforminiandmicrosatellitemarkers.Outof135 sam-plessubjectedtominiandmicrosatellitemarkersamplification, 133samplesweresuccessivelyamplified,2sampleswerepoorly amplifiedbymostofthemarkersusedandwereexcludedfromthe study.
3.2. Markersandallelicvariation
Themajorallelefrequency,genediversity,numberofalleleand polymorphicinformationcomponentacrossall14makersranged from0.24(MS19)to0.64(MS21)withmeanof0.41,from0.57(MS 21)to0.92(MS19)withameanof0.79,from22(ms7)to91(MS 19)withmeanof48.4andfrom0.57(MS21)to0.93(MS19)with meanof0.79,respectively(Table3).MS19makerwasmorediverse
andinformativeandMS21waslessdiverseandinformativethan othermarkersusedinthisstudy.
3.3. T.parvapopulationdiversity
Thediversityacrosspopulationswasdeterminedbythemean numberofdifferentalleles,meannumberofeffectivealleles,mean numberofprivatealleleandexpectedheterozygosity.Themean numberofalleleuniquetopopulationsforCattleclosetobuffalo, Muguga,Njombe,Kibaha,Lushotoand Buffalopopulationswere 0.18,0.24,0.63,0.71,1.63and3.37,respectively.Themean num-berofdifferentallelesrangedfrom6.97(Buffalo)to0.07(Muguga). Mean number ofeffective alleles rangedfrom4.49(Buffalo) to 0.29(Muguga).Themeanexpectedheterozygositywere0.07,0.29, 0.45,0.48,0.59and0.64forMuguga,cattleclosetobuffalo,Kibaha, Njombe,LushotoandBuffalopopulations,respectively(Fig.2).The populationwhichwasclosetoBuffaloinmeannumberofdifferent alleles,effectivealleles,privateallelesandexpectedheterozygosity wasLushotoandthevalueswere6.71,4.17,1.63and0.59 respec-tively.
The results from constructed principle component analysis (PCA)showedthreepatternsofclustering,thebuffalogenotypes whichclusteredonthetoprightquadrantcomprisingthebuffalo individualsandfewgenotypesfromNjombe,KibahaandLushoto; thebottomrightquadrantcomprisingmostofLushoto,Kibahaand Njombeandfewbuffalogenotypes.Thelefttopanddownquadrant wastheadmixgroupcomprisingthegenotypefromall popula-tionsincludingMugugaisolate(Fig.3).Itisinthisquadrantonly wherethecattleclosetobuffalopopulationgenotypeswerefound. Analysisofmolecularvariance(AMOVA)showedhighwithin popu-lationvariation(90%)comparetoamongpopulationvariation(10%) whereasamongindividualvariationwas0%(Table4).
The dendrogramgenerated showed three main clusters, the clusterwheremostofthebuffalogenotypeswerefoundandformed itsownsub-clusterwithonegenotypefromNjombe;thecluster comprisinghighpercentageoftheindividualsfromeach popula-tionexceptMuguga isolate.Inthisclusterthereisasub-cluster comprising only thegenotypesfrom all3 populations ofcattle whichhavenohistoryofco-grazingwithbuffaloes.Thelastcluster wassmallclustercomprisingonegenotypefrombuffaloandsmall numberofgenotypesfromallotherpopulations.Itisinthiscluster wheretheMugugaisolatewasfound(Fig.4).
4. Discussion
Thepopulationgeneticanalysisstudydeploying11miniand 3microsatelliteswasconductedtodetermineT.parvapopulation diversity.Inthisstudyatotalof103and30bloodsamplescollected fromclinicallyhealthcattleandbuffaloes,respectivelywereused. Thestudyrevealedtheprevalenceof70%and49%ofT.parvain cattleandbuffaloesrespectively.Theproblemwasbiggerthanit waspreviouslythoughtbeforepossiblybecauseofthelower sen-sitivityofthemethodswhichareroutinelyusedcomparedtothe p104nestedPCRassaywhich isabletodetectevensub-clinical andcarriercases(Skiltonetal.,2002).Thereishighpossibilitythat mostoftheanimalssampledwereincarrierstate,aphenomenon whichiscommonfollowingnaturalinfectioninbothhostsorpost immunizationincattle(Ouraetal.,2007;Ouraetal.,2011).
Fig.2. Allelicpatternspresentingmeannumberofdifferentalleles,effectivealleles,privateallelesandexpectedheterozygosityacross5populationsandMugugaisolates usedinthisstudy.
Fig.3.Principalcomponentanalysis(PCA)ofT.parvaasgeneratedfrom5populationsandMugugaisolate.Theproportionofthevariationinthedatasetisindicatedineach axis.Theanalysispresentsthreemainclusters;righttopquadrant(purpleovalbordered)comprisingmostofthebuffaloindividuals,lefttopandbottomquadrants(redoval bordered)presentingadmixedgroupandtherightbottomquadrant(blueovalbordered)clustercomprisingmostofNjombe,LushotoandKibahapopulationgenotypes.
Table4
Analysisofmolecularvariance(AMOVA)calculatedfrom5populationsandMugugaisolate.
Sourceofvariation Degreeoffreedom Sumofsquare MeanSquare EstimatedVariation Percentagevariation
AmongPopulations 5 128.67 25.73 0.82 10
WithinPopulations 135 1006.11 7.45 7.45 90
Total 140 1134.79 8.27 100
than0.5(NgonoEmaetal.,2014;Ya-Boetal.,2006).Consequently,
theresultsobtainedinthisstudyareinformativeandshouldbe con-sideredreliableasanassessmentforT.parvapopulationgenetic diversityin theareas assessed.Furthermore thehigh polymor-phismoftheminiandmicrosatellitemarkersusedisrevealedby highmeangenediversity(0.79)andrelativelyhighermeanmajor allelesfrequency(0.41).
TheBuffalopopulationshowedahighpolymorphismcompared tootherpopulationsstudied.Thisissupportedbylargermean num-berofdifferentalleles,effectivealleles,privateallelesandexpected heterozygositythanotherpopulations,followedbyLushoto. Buf-faloesarebelievedtocarryaheterogeneouspopulationofparasites
(Sibekoetal.,2011),therefore;theseresultswerenotsurprising.
Thepresenceofuniqueallelesinallpopulationsindicatethatthere isa uniquesetofisolatesin thepopulationsusedin thisstudy aseachalleleis arepresentativeofadifferentisolate.Thismay compromiseITM,theonlyavailablecontrolmethodofthis par-asitethroughimmunizationsinceguaranteeforcrossprotection amongdifferentisolatesisverylimited(Pelléetal.,2011;Patel etal.,2011).Thevariationoftheindividualswithinpopulationwas furtherrevealedbyAMOVAwhichshowed90%withinindividual variations.
Fig.4.Theneighbor-joiningdendrogrampresentingtherelationshipamong5populationsusedinthisstudyandtheMugugaisolate.Majorityofthebuffaloindividuals formedoneseparatesub-clusterofindividualswhileotherbuffaloindividualsbeingrandomlydistributedinothercattleindividuals.Mugugaformedtheclusterwithfew genotypesfromother5populations.
andonlyalimitedproportionofthebuffalo-derivedpopulationcan beadaptedandtransmittedbetweencattle.Thisstudyrevealeda buffalo-derivedT.parvasub-clusterdifferentfromcattleisolates, thismayaffecttheeffectivenessofITMcontrolmethodsifparasite sharingoccursbetweenthesetwohosts.Parasitesharingismore likelytooccursincepasturesharingiscommonunderthenomadic systemwhichisprevailinginthecountry.
Previouslythere were few casesof ECFreported in Lushoto highlandsandNjombebutthisstudyshowsthatthereisahigh prevalenceoftheparasiteintheseareas.Occurrenceofthe para-siteintheseareasmaybecausedbyextensivemovementofcattle totheseareasforstockestablishment,replacementand search-ingforpasturesfromthelowlandofLushotoandotherpartsof thecountrywherethevectorandparasiteisdominant.Thereisno clearexplanationtowhytheLushotopopulationismorediverse thantherestofcattlepopulationsbutextensiveinfluxofthe cat-tlemaybethereason.Kibahahasbeenpracticingimmunization byITMformanyyearshence;itwasexpectedtobemorediverse thanothercattleisolatesasimmunizationincreasediversityofthe parasite(Weiretal.,2011).Genotypesimilarityanalysisshowed Mugugavaccineisolateclusteringwithgenotypesfromall popu-lationsusedinthestudyasanadmixgroup.Thiswasunexpected sincethereisnoimmunizationwhichhasbeenconductedinthese areasexceptatKibaha.Genotypesharingamongthesepopulations maybecausedbyunrestrictedmovementofcattleamongthese areas.These resultsare concurrent withthose of Mwegaet al.
(2014)whichrevealedgenotypesharingamongMugugavaccine
isolate,EasternandSouthernzoneisolatesalthoughtherewasno vaccinationexercisewhichhadbeenconductedinSouthernzone. Thisstudyrevealed thegenotypic populationstructure of T. parvainareaswheretheisolateswerecollectedfrom.Inthisstudy buffalo-derivedisolateswerefoundtobemorediversethanthe cattle-derivedisolates.Thissituationposesmoreriskonthe sus-tainabilityofITMinthefeatureduetouncontrolledmovementof cattlewhichmayleadsub-populationsofT.parvafrombuffaloes toadapttocattlesinceparasitesharingbetweenthesetwohostsis
possible.Ontheotherhandtherewasnostrongevidenceshownby thisstudyonparasitesharingbetweencattleandbuffaloesgrazing inthesamearea.Itisstillpossiblethatsharingofisolatesmaybe occurringbutwasnotevidentgiventherelativelysmall popula-tionexaminedinthisstudy.Therefore,itissuggestedthatfuture studiesbeconductedincludingmoresamplesfromcattlethatare co-grazingwithbuffaloes.Thiswillhelptoestablishthepotential risksofcross-infectionbetweencattleandbuffaloesgrazinginthe samearea.
Financialsupport
We want toacknowledge the financial supportprovided to theBiosciencesEastern and Central AfricaHubat International Livestock Research Institute (BecA-ILRI Hub) by the Australian AgencyforInternationalDevelopment(AusAID)througha partner-shipbetweenAustralia’sCommonwealthScientificandIndustrial ResearchOrganisation(CSIRO)andtheBecA-ILRIHub;andbythe SyngentaFoundationforSustainableAgriculture(SFSA);theBill &MelindaGatesFoundation(BMGF);andtheSwedishMinistry ofForeignAffairsthroughtheSwedishInternationalDevelopment Agency (Sida). The financial support granted by Eastern Africa AgriculturalProductivityProgramme(EAAPP)onfieldsamples col-lectionishighlyappreciated.
Conflictofinterest
Acknowledgement
We send our sincere gratitudeto Joyce Njuguna and James Wainainafortheirvaluablesupportondataanalysis.
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