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Anemia in Experimental African Trypanosomiasis
Ogbadoyi, Emmanuel O., Ukoha, Agwu I.,
Kyewalabe, Elizabeth K.
The Journal of Protozoology Research, 9(2): 5563
1999-04
http://ir.obihiro.ac.jp/dspace/handle/10322/317
The Research Center for Protozoan Molecular
Immunology
帯広畜産大学学術情報リポジトリOAK:Obihiro university Archives of Knowledge
J.Prot()ZOOI.Rcs.,9,55−6ユ(1朔)
C叩γrfg加⑥Jタワ夕.mど月ど∫gd′dC〝眈rβrPr〃加㈹柁〟bJど川血rJmm〟〃ロわgγ
AnemiainExperimentalAfricaLnTiypaJ10SOmiasis
EMMANUEL O.OGBADOYIl),AGWUI.UKOHA2)ANr)
ELIZAl∃ETH K.KYEWALA13E3)
/舶那加鋸肋止血椚叫′Z〟γれ好打d】川〟5上月fg′ⅣJgビrれ2D叩招rfmど”′げ別oJ咽fc〟J5c椚−Cど5′
Fビ加r〟川′∼加r5和好花eJ川OJpgy′旭〃闇′Nfgどγれヱ翫pf亡〟JDf5ビ〟5ビS尺ど5ビβrr7−Cピ〃恒ノ
P.0.月8エ7コ7占g′N由れZ爪肌あ㍍
Rccej−−edlM町Ch】9りウノAl℃ePledlユAprilL9粥
Kcywords:丁わp【1〃0∫∂〝MリルdJ.■anemia;meChanjsm=r)’panOSOmiasi5.
ABSTRACT
Anemiaisarecognizedfeatureofbothanimalandhumantrypanosomiasis・
Themechanismoftrypanosomalanemiaishoweverunknown.Understandingthe
TrleChanism of anemiaisimportant for the effeetjve management of
trypanosomiasispatients,eSpeCiallylnanimalswhereanemiacouldbeextremely
SeVere,Anemia was monitoredin five goats experimenta]lyinfectedwith
Tbpanosoma vivax by measuring the packed ce11volume(PCV)and the
hemoglobinlevel(Hb)upto26dayspostinfection.Parasitemiaandserum free
fattyacid(FFA)1evelswerealsoestimated.Massiveparasitemiawasobservedon
days5and12postinfection・Therewa545−59%decreaseinthePCVand33−63%
decreaseinthe Hblevel.Theserum Fl仏1evelproBreSSivelylnCreaSedthrough
Outthecourseofinfection,Anemiaintheearlystagesoftheinfectionisinitiated
andmaintainedbylivlngtryPanOSOmeS,the severltyOftheanemiadependingon
thelevelofparasitemia.Persistent anemiaasthe disease processprogressesis
CauSedbyfactor(S)otherthanlivingtrypanosomes.Itissuggestedthaterythrocyte
haemolysIS and erythrophagocytosis are the underlylng CauSeS Of trypanosomal
anem】a.
INTRODUCTION
Africantrypanosomiasesare aspectrum ofdiseasesin mananddomestic
animalscausedbythetsetsetransmittedprotozoanparasite,tryPanOSOme.Huma
African trypanosomiasis(Sleeping sickness)is caused by TbpanoL”ma bruceE
ま∫
ANEMlA 1N AFRlCAN TRYPANOSOMlASlS
gambienseandT.b・rhodesiense・Animaltrypanosomiasis(naganaincattle)onthe
Other handiscausedbythreespeciesoftrypanosomes,namely T.b.brucei,T.
COngOZenseandT.vivax.Ofthesethreetrypanosomespecjes,T.vivaxisthemos
important trypanosome of veterinary importance in West Africa. Animal
trypanosomiasissti11constitutesamaJOrCOnStraintinthegrowthanddevelopment
Of thelivestockindustryin many eountries of sub−Saharan Africa,thereby
limiting10talfoodproduction.AnimaltrypanosomiasisandEastCoastfeverare
believed toaccountforthe deathof3mi11ion cattle ayearand oneor bothOf
these diseases occur(S)across morethan one third of the African continent
(ILRAD1987).The estimated annuallossinlivestock due to African
trypanosomiasisisputatUS$5,000mi11ion(WHO1997).
Anemiahassincebeenrecognizedasam叫OrpathologlCalfeatureofclinical
trypanOSOmiasisintx)thmanandanimals(fiennes1954;1970)andhasbeenused
as anindicator of trypanotolerancein animalsinftcted with trypaT10SOmeS
(Akinbamijoetal.1998;drIterenetal.1998).However,tOdate,themechanism{)f
the anemiais unknown.Rather,hypo血eses whichhave failed t0月nd common
grollndofacceptablespecincityhavebeenputforward.Theseinclllde:hypoplasia
Ofthe bonemarrow,hydraemia,immunologlCalreactions,erythrophagocytosis,
hemorrhagesyndromeandseverehaemolysis(reviewedbyMurrayandI)exter
1988).AmorerecentadditiontothislistofhypothesesisthereportofIgbokweet
al.(1994)thatperOXidativeipjury to erythrocytes may play a rolein the
pathogenesis of anemia in trypanosomiasis. A good understanding of the
PathogenesisoftheanemiaisimportantforabettermanagementofthepatieIltS,
espeCla11ylnanimaltrypanosomiasiswheretheanemiacouldbeverysevere・This
Studyis part ofour contribution to the efforts towardsthe elucidation ofthe
mechanismofanemiaintrypanosomiasis・
MATERIALS AND METHODS
什り柚町、・岬‥、−
Tbpanosomavivaxstabilate,StOCkKabam/84/NITR/7・4wasobtainedfrom
the NigerianInstitute for Trypanosomiasis Research,Vom,Nigeria.This was
inoculatedinsheep■sbloodandkeptlnliquidnitrogenat−196bcbeforebeingused
ingoats.
(JIMJ∫.・
GoatswerepurchasedfromlocalmarketsinZaria,NorthernNigeriaand
keptinfly−prOOf perISin the facu]ty of veterinary medici11e,Ahmadu Bello
Universlty,Zaria・ApproprlateStepSWeretakentoensurethatallthegoatswere
ingoodhealthandapparentlyfreefromtrypanosomiasisandanyotherformof
ぎ首
ANEMlA IN AFRlCAN TRYPANOSOMlASlS
ParaSiticinfectionbeforetheexperimentalinfection・
Cんβ椚fc(】血.・
Unless otherwise stated,a]1chemicals used were obtained from Sigma,
England,andwereallofanaJytlCalgrade.
均匹雨脚舶用抑血肌
Tengoatsweredividedinto2groupsof5each・Onegroupof5wereeach
infectedwithlO7T.vivaxce11swhilethesecondgroupof5wereuninfectedand
servedascontrol.
PdJⅥ∫fJg椚Jdα〃dク〟CたどdcβJJt,OJ〟用ビrPCVノご
Parasitemia and PCV were deterrnined usJng the haematocrit centrifuge
technique(W〔)0】97())・
〃g椚〃gJぴぁf〃“ノ〃Jピ〃J.■
ThehemoglobincontentwasestimatedbysimplytakingalittlequantltyOf
bloodsampleandthenreadingoffthehemoglobinlevelinaCounter
haemoglobinometer.
J、、〃〃J・い用い、い‥、州、川・声い・い.トJJl・∫・・バ・
FFAlevelswereestimatedasdescribedbyFalhoILetal.(1973)・Allthe
parametersweremeasuredessentiallytwiceaweek,beginnlngfromdayOtoday
26postinfection・
REStTLTS
PりJ・り∫情,川扇.、
Therewerecyclicalnuctuationsinthenumberofparasitesincirculation
whichresultedin3successivewavesofparasitemiawithpeaksondays5,12and
22postinfection(Fig.1).Between days5and8,the number oIlparasitesin
Circulation decreasedsharply,reaChingaverylowlevel(1essthan halfthepeak
Value)by day8・The second phase ofdeclining parasitemia whjch was rnore
drasticthanthefirstocc11rred betweendays12and19postinfection・Byday19,
thelevelofparasitemiawasthesameasthatonday2(6timeslessthanthepeak
Value on day12).Thepeak valueson days5and12were the sal一一e(about4
trypanosomes per microscopefield),While the value for day22was aboutl
lrypanosomeperfield.Theva]uesg】VenareanaVerageOfthevaluesforthefive
gOatS・
ANEMtA TN AFRICAN TRYfnNOSOMIASIS
Figurel・DeveJopmentofparasitemiathrough
山e course orin托ction.Ani11uslmtわn of 仇e
CyClical fluctuatJOnSin parasitemia duriTlg the
VeJticalbars represent standard errors of mean
つL
吋叫EO︼叫S已dh
COurSeOftheex匹hmen血infecltonwhich】a$ted
払ー払days.臨chpointon仙eve摘録1axisisthe
m組nOf也eYalueso一也efiveh触短dgoats.The
(SEM).
Ul
∈)
れ
⊂〉
■・→r−M
レ「
r】
Q
{
Day5(pDStimfecLion)
J,油・Å.・.J.・lJ/い巾〃Iけり一(l−Jご
Ⅶth the exception of goat number3808which showed no apparent
decreaseinPCVbyday2postinfection,thePCVofalltheinfectedgoatsshowed
Signi鮎antdecreasesbyday2,withasmuchas25%decreaseingoatnumber3845
(Fig.2).Thedecreaseattheendoftheexperimentranged between45−59%.In
general,therewasaprogressivedecreaseinPCVofa11theinfectedgoatsuntilthe
terminationoftheexperiment.
Figure2.The packedcelJvolum芦Ofdle
im飴ctedgoatsdurlngthepeddofinfection
This shows the decliningPCV duringthe
26rday period of expenmentalinfection.
Eachpo)ntOntheverticalaxisistheneanof
仙e valu8SOfthe flveinfヒc便d go且暮SWhile
the SEM are represented by the ve鵬cal
bars.
C
>「
【=)
r【†・・」N
Ln
「】
く=〉
rl
D往)・S(POStinf¢C暮ipn)
〃g椚¢gわぁ血「励ノ励gJ.・
LikethePCV,theHblevelsofa11theinfectedgoatsdecreasedsignificantly
朗
ANEMIA TN AFRTCAN TRYPANOSOMTASTS
duringthecourseofinfectionwithanaverageof48%reductionexceptforgoat
3844whichhaditshemoglobinlevelreducedbya5muChas63%beforeitfinal1y
died(Fig.3).
Figure 3.The hemoglobinlevels ofthe
infected goatsduTlr[gtheperiodofinfeetion.
Thisillustrates(he decreasein Hb]evels with
VeJticalbarsrepresentSEM.
ムり
︵一pも︶芯已t上H
progressiorlthroughthediseaseproces5■7hch
poJntOr)dle Vertic且1axisIsthe mean ofthe
Ya山es of山e fjYeinfected goats while the
く︶
⊂〉
ln
⊂⊃
レ1
⊂コ ー・{−・{M
「】
r′
ロays(pos【infec【i8n〉
∫gr〟椚/佗gβrJγ〟Cfdr錯弓りJgveJニ
TherewasaprogressiveincreaseintheserumFFAlevelofalltheinfected
goats(Fig・4)・Thevaluesofalltheparametersmeasuredina11thecontrolanimals
did not show any appreciable change but remained essentially constantwitll
∝CaSionaldroporrisebylunit(datanotincluded).
Figure4・Serumfreel加yacid(FFA)1evels
Of血ein托ctedgoats.Ser11mFEAlevelsoflhe
infected goats measured over the 26−day
PerlOdofinfection・EachpoJn10ntheverticaI
axisis the mean of the va]ues of the nve
ex匹nmenta11yinfected goats,Vellicalbars
r叩reSentSEM・
⊂⊃l(
(つレ1
く⊃
「」
lハ
⊂⊃
「l r’ ̄
D8yS(postinfec【ion〉
且9
ANEMlA 1N AFRlCAN TRYPANOSOMlASlS
DISCIJSSION
AnemiaintrypanosomiasisproceedsintwodistinctbutoverlapplngPhases,
eachphasebeing mediatedbydifferentmechanisms(Murray andDexter1988)・
Thefirst phaseis believedto bemediated byfactors releasedby degeneratln
trypanOSOmeS(Tizzardetal.1978b;ILRAD1987)andredcelldamagebyliving
trypanosomes(Banks1979;Esievo1983).Ourobservationsinthisstudyarein
SuppOtt Oflivlng tryPanOSOmeS Playlng a key rolein theinitiation and
maintenanceoftheprogressivedevelopment ofanemiaintrypanosomiasis・The
onset ofanemia andthe severltyimthe nrst phase strongly correlate witht
appearance,intensity.and durationofparasitemia・Theobserved considerable
declineinthePCVandtheHbcontentbetweendaysOand5postinfectionandthe
relativelystablevaluesbetweendays5and8(Figs・2and3)whichcoincidedwith
increasinganddecreasingparasitemiarespeCtively(Fig.1)couldnothavebeena
merecoincidence.ThePCVandHbcontentagaindecreasedsharplybetweendays
8and12which wasanOther period ofincreaslng paraSitemia・ThesefindiTlgS
SuggeStthatlivlngtrypanOSOmeSareeSSentialfortheprogressivedevelopmen10f
trypanosomalanemiaininfectedamimals・Ikedeetal・(1977)reportedtheabsence
OfhaemolyslnintheplasmaofT.congolenseinfectedmiceatleastupto15days
POStinfectionbutobservedmarkedreductioninerythrocytehalf−1ifeandmarked
dropin PCVwithin the same period.In cattleinfected with T・COngOlense
increasedred cellbreakdownisbelievedtocommence withthedevelopmentof
parasitemia(HoImes1976;Prestonetal・1979)・Thereforecontrarytothewidely
heldviewthatanemiaintrypanosomiasisisinducedbyfactorsreleasedbydying
trypanosomes,Webelievethattheonsetofanemiaanditsprogression,atleastin
the early stages ofinfectioT),dependslargely on the presence oflivlng
trypanosomesincirculation・
ThepersistentanemiaevenwhenparasitesarebarelydetectabIeisthephase
IIoftheanemia・Webelievethatthisstageismediatedbyfactorsotherthanthose
producedbylivlngtryPanOSOmeS・FFAsandLysophospholipidsarebelievedtobe
hemolytlC factors released by dying trypanosomes and are responsible fo
trypanosomalanemia(Tizzardetal・1978a;Noketal・1993)・Weobservedsteady
andsharplnCreaSeSintheFFAlevelsofalltheinfectedgoatsthrough outthe
period ofinfection(Fig・4)and this could have played a key roIeiTlthe
pathogenesisoftheperSistentanemia・Althoughserumalbuminisknowntobind
toFFAstoneutralizetheirhemolyticeffects(StarinskyandShafrir1970;Tizzard
etal.1978b),itispossiblethatthema5Siveparasitemiathatcharacterizedthefirst
twosuccessivewavesofparasitemiaproducedsufficientFFAstosaturateavai1abl
serumalbumin and someleft unbound to exert their hemolytlC effect on
erythrocytes・
甜
ANEMIAIN AFRICAN TRYP4NOSOMTASIS
Elucidationofthemechanismofanemiaintrypanosomiasishasremainedan
unsoIvedproblem・Jenningsetal,(1974)suggestedthatanemiaintrypanosomiasis
WaSmainlyduetoextravascularhaemolysIS andruledoutirnmunemechanisms
Sinee(heonsetofanemiawasevidentwithinafewdaysofinfection・Murrayand
Dexter(1988)explainedthaLimmunologicalcompetencewasnotessentialforthe
developmentofanemia.DargieetaJ.(1979a;1979b)andDargie(1980)ruledout
haemodilution as a contributory factor to the development of anemia・
Hemorrhagic syndrome whichis characteristic of acuteinfections caused by
Certainstrains ofT・Vivaxinfections wasnotevidentin thepresent study.The
markeddropinPCVandthemarkedreductjonintheHbconten(Observedin[his
WOrkaregoodindicatorsofhaemolysis・Wethereforebelievethatthefirstphase
Ofanemiaislargelyduetoerythrocytehaemolysis.Erythrophagocytosis resultin
frominducedalterationsinerythrocytesurfacestructure(Durocheretal.1975;
Esievo et al・1982;Esievo1983)is alsoapossibility as acauseofanemiain
trypanosomiasis. We therefore conclude that trypanosomal anemia is
multifactoriallyinduced butthe predominantfactorsdependonthe stageofthe
diseaseprocess.
ACKNOWLEDGEMENTS
This study was funded by a research grant from the Ahmadu Bello
Universlty,Zaria,Nigeria,tOAgwuI.Ukoha.The authors are gratefulto:Mr.
RaphaelandMa11amBalla,bothof(heDepartmentofVtterinaryParasitology;Dr・
Jagun of the Nationa]AnimalProduction ResearchInstitute,Zaria for their
technical assistance and Professor K. A. N. Esievo for allowing us to use
haemoglobinometer.
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