COMPLETEBLOODCOUNT

Asageneralrule,Idonotrecommendlaboratorytestsonclinicallyhealthy“petbirds”thatarebroughttomeforroutinephysicalexaminationandgroomingonaregularbasis.Inmyexperience,ifabirdisactingnormalathome,ifIseenothingabnormalontheexam,theninalllikelihoodlaboratorytestswillbenormalaswell.Thatbeingsaid,therearetwobasictests(whichcanberequested)thataregood,additionalindicatorsofhealth;thefecalGramstainandthecompletebloodcount.TheGramstainisdiscussedinaseparatepaper.Thecompletebloodcount(CBC)isagood,sensitiveindicatorofthebird’sgeneralhealth.Achangeinthehemogramcanbenotedwhennootherabnormalitiesaredetected.Itisthesinglemostimportantbloodtestthatcanbeperformed.IfallparametersarenormalontheCBC,thenthisisagoodindicationthatthebirdisnotcurrentlyfightingsometypeofgeneralizedinfectionorinflammatorydiseaseprocess.However,anormalCBCdoesnotruleoutthepossibilitythatthebirdisanasymptomaticcarrierofabacterialorviraldiseaseorhasalocalizedinfection.TherearethreetypesofcellswhichareevaluatedontheCBC;redbloodcells(RBC’sorerythrocytes),whitebloodcells(WBC’s)andthrombocytes.Inaddition,theplasma(non‐cellularpartoftheblood)isexaminedforcolor,protein,andthepresenceofparasites.ThefollowingisalistofparametersmeasuredontheCBCwitharangeofnormalvalues.Valuescanvarygreatlybecausetherearesomanydifferentkindsofpsittacinebirds.Therearealsodifferencesbetweenjuvenilesandadults.

CBCPROFILEPARAMETER RANGEOFNORMALVALUESRBC(millionsofcells/cumm) 2.5–4.5PCV%(packedcellvolume) 42–55Polychromasia slt(slight)Anisocystosis sltMCV 100–200WBC(cells/cumm) 5000–15000Heterophils% 40–75Lymphocytes% 20–50Basophils% 0–5Eosinophils% 0–2Monocytes% 0–3Buffycoat% 0–1 COMMENTS noneThrombocytes presentPlasmaColor clearorpaleyellowTotalprotein(gm/dl) 2.5–5.5Parasites none

REDBLOODCELLSExaminationoftheerythrocytesprovidestheveterinarianwithinformationconcerninganemia‐relatedproblemsandthebonemarrowresponse(whichiswhereRBC’sareproduced).Inahealthybird,mostRBC’sshouldbemature,butasmallpercentageofimmatureerythrocytesisexpectedwhichindicatesanormalreplenishmentfromthebonemarrow.ImmatureRBC’sareslightlylargerthanmatureRBC’sandthecytoplasmislightlystippledwhichproducesadifferenceincolor.ANISOCYTOSIS(sizevariationbetweenRBC’s)andPOLYCHROMASIA(colorvariationbetweenRBC’s)aretermsusedtoindicatethepresenceofimmatureRBC’s.OntheformusedtoindicatetheresultsoftheCBC,aslight(slt)responseisnormalwhilemoderateormaximumindicatesastrongbonemarrowresponsetosometypeofanemiaproblem.Ifabirdisanemicandshowsslighttonopolychromasiaoranisocystosisoveraperiodofseveralweeks,thiscanindicatethatthebonemarrowisdepressedornon‐regenerativewhichisagravesituation.Meancorpuscularvolume(MCV)isameasurementoftheaveragesizeofRBC’s.Thevaluerisesinanemicconditionsthatareregenerativebecausenewlyproducedredbloodcellsincreaseinnumbersandthesecellsarelargerthanmaturecells.Ifthevalueisbelownormalandthebirdisanemic,thenthisindicatesanon‐regenerativestate.Anemiameansadecreaseinthenormalamountofredbloodcells.ItcanbeduetoeitherbloodlossorlackofproductionofnewRBC’sfromthebonemarrow.TheratioofthevolumeofRBC’stothevolumeofwholebloodiscalledthePACKEDCELLVOLUME(PCV).Thisnumberisexpressedasapercentage.Itisdeterminedbyputtingasampleofbloodinatinycollectingvialcalledamicrohematocrittube.Atthelaboratorythistubeisspuninacentrifugewhichseparatestheredbloodcellsfromtheplasma.Inanormal,healthybird,thePCVrangesbetween42–55%.Smallbirdssuchasbudgiesandcockatielsaverage50%orhigherwhilethevaluesinlargerspeciesareusuallylower,between42‐45%.Anyvaluelessthan35%indicatesanemiaandobviouslythelowerthevalue,themorecriticalthecondition.Valueshigherthan55%aremostoftencausedbydehydration.

TheactualnumberofRBC’scanalsobecounted,usingeitherautomatedcellcountingmachinesorbymanualtechniqueswhichprovidegoodestimates.ThenumberofRBC’sisrecordedasanumbertimes10tothesixthpowerwhichmeansmillionsofcellspercubicmillimeter(cumm)ofwholeblood.ThenormalnumberofRBC’svariesdependingonwhetherthebirdisajuvenileoradultandthekindofbirdbeingexamined.Ingeneral,mostadult,healthypsittacinesaveragearound2.5–4.5millionRBC’s/cummofblood.Asabirdbecomesanemic,thenumberofRBC’sdecreases.WHITEBLOODCELLSWhitebloodcells(WBC’s)arepartofthebody’sdefenseorimmunesystem.TherearefivetypesofWBC’sfoundinbirds.Heterophils,eosinophils,andbasophilsareknownasgranulocytesbecausetheyallcontaincoloredgranules(tinyspindleshapedbodies)intheircytoplasm.Thesecellsareallproducedinthebonemarrow.LymphocytesandmonocytesareknownasmononuclearWBC’s.Thesetwotypesofcellshaveasinglenucleusandnogranulesintheircytoplasm.Theyoriginateinthespleenandintinycollectionsoflymphoidtissuefoundthroughoutthebodyasopposedtothebonemarrow.DuringthecollectionofbloodforaCBC,atinydropisplacedonaglassmicroscopecoverslip.Asecondcoverslipisplacedontopandthetwoarepulledapartcreatingabloodsmearonecelllayerthick.Backatthelaboratory,thissmearisstainedwithabluedyewhichcolorsthedifferentcellssotheycanbeidentified.Bylookingatthesmearunderthemicroscope,thetotalwhitebloodcellcountcanbeestimatedaswellasdeterminingthenumberandrelativeproportions(%)ofthefivedifferenttypesofWBC’s.Inaddition,theWBC’scanbeexaminedforabnormalcharacteristics.Allthesefindingsaresignificantindeterminingwhetherabirdisfightingsometypeofdiseaseandhowseriousitis.

WHITEBLOODCELLCOUNTThetotalWBCcountcanalsobedeterminedbyphysicallycountingallofthegranulocytesinadilutionofwholebloodthatisstainedandputinacellcountingchambercalledahemacytometer.Thecytoplasmicgranulesofthesecellsarespecificallyhighlightedbythedyewhichmakesthemeasytocount.ByalsoknowingthepercentageofmononuclearWBC’spresentfromthebloodsmear,onecanarriveatafairlyaccuratetotalWBCcount.ThenormalWBCcountcanvaryfromlaboratorytolaboratory.Itisdependentonthestainingqualityofthesmearandtheproperidentificationofcells.Inthelabweuse,thenormalWBCcountinadultpsittacinesvariesbetween5000‐15000cells/cummofblood.Insmallerspecies(i.e.budgies,cockatiels)thenormalrangetendstobelower(5000‐10000cells/cumm)thaninlargerspeciessuchasAmazonsandmacaws(12000‐15000cells/cumm).JuvenileparrotsusuallyhavehigherWBCcountsthanadults.Itisnotuncommontoseecountsinthe20000‐25000cells/cummrangeinlargepsittacinesthatarenearweaningage.Acrude,rapidtechniqueforestimatingiftheWBCcountishighisbymeasuringtheBUFFYCOAT.Whenthemicrohematocrittubeisspunatthelaboratorythereisatinylayerofwhitecellsthatseparatesoutatthejunctionbetweentheredcellsandplasma.Thisiscalledthebuffycoat.Inanormal,healthypsittacinebird,thebuffycoatshouldbe1%orlessofthetotalvolumeofblood.Abuffycoatof2%orhigherindicatesahighWBCcount.6%isthehighestamountourlabhasevermeasured.AnincreaseintheWBCcountiscalledleukocytosis.Acommoncauseofleukocytosisistheactualtransportingandhandlingofabirdattheclinic.Thisisaphysiologicalchangeduetostress.Diseasecausesincludebacterialandfungalinfection,psittacosis,avianTB,trauma,toxicities,andcertaincancers,suchasleukemia.AdecreaseintheWBCcountiscalledleucopenia.Themostcommoncausesofthisincludeacuteviralinfectionsandtheendstagesofoverwhelmingsepticemia(bloodpoisoning)inwhichthebodyliterallyrunsoutofWBC’swithwhichtofightwith.

ThepercentageofthedifferenttypesofWBC’siscalledthedifferential.Asstatedbefore,alternationsofthedifferentialfromthenormalrangeandchangesincellcharacteristicsaresignificantforvariousdiseaseconditions.HETEROPHILSTheheterophilisthemostcommongranulocytefoundinpsittacinebirds.Thenormalpercentageofheterophilsisbetween40‐75%.Itisconsideredthe“windowtothebird’sstateofhealth”sinceevensubtlechangesinnumbersandcharacteristicscanoccurwithproblemssuchasstress,low‐gradeinfection,andmildinflammation.Thesecellsareinstrumentalinthebody’sdefensewithincrediblylargenumbersbeingavailabletodestroyandengulfbacteriaorotherinfectiousagentsseeninacuteoroverwhelminginfectionandinflammationHeterophilsexhibittoxicchangesinstressordiseaseconditionsthatcanbeseenmicroscopically.Alowdegreeoftoxicityiscalleddegranulation.Thisisseenasadecreaseinthenumberandsizeofcytoplasmicgranulesandachangeincolorofthecytoplasmfromcolorlessorlightbluetoamuddypinkorredcolor.Ifdegranulatedheterophilsareseenonthebloodsmear,thiswillbenotedundertheCOMMENTSsection.Ifnothingiswritten,thenthismeansalltheheterophilsappearnormal.Milddegranulationofheterophilscanbeconsiderednormalinbirdsunderstress.However,thisfindingshouldalerttheveterinarianthatsomethingisgoingon,especiallyifthetotalWBCcountishigherthannormal.Insevere,generalizedillnesses,theWBCcountmayriseabovenormalwithavaryingnumberoftheheterophilsappearingdarkandshrunken.Inadditiontodegranulation,thesecellsmayappearfoamy(thepresenceofvacuolesinthecytoplasm),ortohaveruptured.Thepresenceofbacteriamayalsobeevidentinthecytoplasm.Suchheterophilsaredescribedasbeingtoxic.Thedegreeofheterophiltoxicityusuallyincreaseswiththeseverityofthebird’scondition.Birdshavingahighdegreeoftoxicityinmostoralloftheirheterophilsoftenhaveagraveprognosis.Thisisespeciallytrueifleucopeniaispresent.

EOSINOPHILSANDBASOPHILSEosinophilsaresimilarinappearancetoheterophilsbutcanbedifferentiatedbythecolorandshapeoftheircytoplasmicgranulesandthedarkerstainingnucleus.Eosinophilsoccurinverysmallnumberswiththenormalrangeconsideredtobe0‐2%.Thefunctionoftheavianeosinophilisunclear;however,increasednumbersaretypicallyassociatedwithparasiticinfections,allergicreactions,andsignificanttissuedamage.Changesincellmorphologyhavenotprovenhelpful.Basophilsareeasytoidentifybecauseoftheirdark‐staining(basophilic)cytoplasmicgranules.Theyalsooccurinsmallnumberswithanormalrangeof0‐5%.Theexactfunctionofthebasophilisnotknown.Increasednumbersareoftenassociatedwithchronic,longtermillnesses.Theyalsoappeartoplayaroleintheearlystagesofinflammation.LYMPHOCYTESLymphocytesandheterophilsarethemostnumerousWBC’sseeninpsittacinebirds.Thenormalproportionoflymphocytesis20‐50%butitvariesbetweenspecies.SomespeciessuchascockatielsandAmazonparrotsarenaturallylymphocyticwhichmeansmorelymphocytesthanheterophilsareseennormally.Lymphocytesareaveryimportantpartofthebird’simmunesystem.Lymphocytesincreaseinnumbers(lymphocytosis)incertaintypesofchronicinfectionsandlymphoidleukemia.Theydecreaseinnumbersinacuteviralinfections.Inadiseasestate,lymphocyteswillbecomereactive.Microscopically,thenormallypalebluecytoplasmbecomesmulti‐coloredwithlightblue,clear,andpinkareasandthecytoplasmbecomesvacuolated(thepresenceoftinybubble‐likestructures).Inchronicconditionslymphocyteswithazurophilic(purple)granulesinthecytoplasmhavebeennoted.Afewreactivelymphocytesonabloodsmearisnormalbutifmanyarereactivethenthisisasignificantfindingthatthebodyisrespondingtoaninfectionofsomesort.Ifreactivelymphocytesarepresent,thiswillbenotedundertheCOMMENTSsection.Reactivelymphocytessynthesizeantibodiesandotheragentsinvolvedinthehostimmunesystem.

Birdswithamarkedlymphocytosisinwhichmostorallofthelymphocytesappearabnormalorimmatureisconsistentwithleukemia.TheWBCcountinsuchbirdscanbegreaterthan100,000cells/cummofwhichmostarelymphocytes.MONOCYTESThesearethelargestWBC’sfoundinavianbloodandtheyareverysimilarinappearancetolymphocytes.Theyoccurinsmallnumberswithanormalrangeof0‐3%.Anincreaseinthepercentageofmonocytes(upto10%)isseenwithcertainchronicdiseasessuchaspsittacosis,systemicfungalinfections,TB,andmassivetissuedestruction.Changesincellmorphologyarenotsignificant.TheevaluationoftheWBCcount,thedifferential,andcellmorphologyisveryusefulintheassessmentoftheprogressofanavianpatient.Forexample,abirdwithaninitialleukocytosis,increasedheterophilswhichappeartoxicandreactivelymphocyteswouldbeshowingafavorableresponsetotherapyifthetotalWBCandheterophilcountsweredecreasing,thetoxicheterophilshaddisappeared,andthereactivelymphocytesreturnedtonormal.THROMBOCYTESThrombocytesarethethirdtypeofcellsfoundinavianbloodandtheseareactiveparticipantsinbloodcoagulationorclotting.Birdsdonothaveplatelets(cellcytoplasmicfragments)whichperformthisfunctioninmammals.Thrombocytesareproducedinthebonemarrow,areslightlysmallerthanerythrocytes,andareoftenclumpedtogetherinsmallnumberswhenviewedonabloodsmearunderthemicroscope.Inadditiontobloodclotting,thesecellsmayhavetheabilitytophagocytize(oreat)bacteriaandforeignmaterial(likesomeWBC’s)andtheymaybeabletocarryoxygen(likeRBC’s)ifanextremeanemicconditionexists.

DuringtheCBCevaluation,thepresenceofthrombocytesisnotedontheformandifthenumbersseemdecreasedorincreased,thisisalsoindicated.Increasednumbersofreactivethrombocytescanindicateachronicdiseasecondition.PLASMAPlasmaisthefluidportionofbloodinwhichparticulatecomponentsaresuspended.Plasmaisdistinguishedfromserumwhichisthecell‐freeportionofthebloodfromwhichfibrinogen(bloodclottingfactors)hasbeenseparatedintheprocessofclotting.WhenbloodisdrawnforaCBC,thecellcomponentsneedtobeevaluated;therefore,thebloodmustnotclot.Heparinistheanticoagulantofchoiceinbirds.ThemicrohematocrittubesorlargervialsusedtocollectbloodforaCBCareheparinizedtopreventcoagulation.ColorAfterthemicrohematocrittubeisspunatthelaboratorytheplasmaisvisuallyexaminedforcolor.Inmostbirdsitshouldbeclearorpaleyellowincolor.Theyellowcolorisduetothepresenceofcaroteneswhichareyellowpigmentsfoundinavarietyofplantmaterials,includingsomeseeds.Yellowcoloredplasmashouldnotbemisinterpretedasictericplasma.Inmammals,icterusorjaundiceisduetoincreasedamountsofbilirubinpigmentsinplasmaasaresultofliverdisease.Birdsdonothavebilirubin;thereforetheydonotbecomeictericiftheyhaveliverdisease.Sometimestheplasmaappearspinkincolor.ThisisduetohemolysiswhichisthebreakingapartofRBC’sandthesubsequentreleaseofredhemoglobinmoleculesintotheplasma.Hemolysisismostcommonlycausedbyimproperhandlingofbloodsamples,suchasforciblyexpellingbloodthroughtheneedleofthesyringe,shakingratherthansimplyinvertingthetubetomixbloodwiththeanticoagulant,overcentrifugation,orfreezingandthawingofthesample.Sometoxicitiescancauselysisofbloodcells,themostcommonexamplebeingleadpoisoning.Occasionallyanoverwhelminginfectioncausingsepticemiawillalsocausehemolysis.

Theplasmacanalsoappearwhiteormilkyincolorwhichisduetothepresenceoffat.Thisiscalledlipemia.Lipemicplasmaismostcommonlyseenifabloodsampleisdrawnshortlyafterthebirdeatsamealhighinfat(i.e.oilyseeds).Sometimesifthebirdisexcessivelyoverweight,theserumwillalwaysappearmildlylipemic.Liverorpancreaticdisorderscancauselipemia.Lastly,infemalebirdsthatarereproductivelyactive,theplasmawillbelipemicduetoyolkglobules(fatsandprotein)whicharesynthesizedintheliverandtransportedviatheplasmatotheovarywheretheyareincorporatedintheoocyte.TotalProteinWhileplasmaismainlywater,itdoescontainasubstantialamountofprotein.Mostplasmaproteins,withtheexceptionofantibodiesandhormones,aresynthesizedintheliver.Proteinsformthebasisoforganandtissuestructure,operateascatalysts(enzymes)inbiochemicalreactions,areregulators(hormones),andarethetransportandcarriercompoundsformostoftheconstituentsofplasma.Thetotalproteinlevelintheplasmaisoftenusedasanindicatorforthehealthstatusofthepatient.Themeasurementoftotalproteinisasimpletesttoruninthelaboratory.Mostpractitionersuseaninstrumentcalledarefractometerwhichgivesagoodestimateoftheproteinlevelaslongastheplasmaisclear.Hemolysisorlipemiawillgiveafalselyelevatedlevel.Thenormalvalueforpsittacinespeciesisinarangebetween2.5‐5.5grams/deciliter(g/dl).Lowtotalproteincanreflectchronicdisease(especiallyliverandkidneydisorders),cancer,parasitism,longtermstress,andstarvationormalnutrition.Increasedvaluesmayindicatedehydration,chronicinfection,orleukemia.PARASITESBloodparasiteswereoftenfoundinthebloodsmearsofwild‐caught,importedbirdsinyearspast.Howevertheyareextremelyrareindomestic‐raisedpetbirdsthatarekeptindoors.Bloodparasitesaretransmittedbybloodsuckinginsects(flies,mosquitoes,ormites)andwhethertheycauseclinicalsignsofdiseaseisdeterminedbythe

typeofparasitefoundandthespeciesofbirdinvolved.Ingeneral,mostbloodparasitesfoundinpsittacinebirdsareincidental,willcausenoclinicaldisease,andtreatmentisusuallynotrecommended.ParasitesthatinvaderedbloodcellsincludeHemoproteus,Plasmodium(avianmalaria),Leukocytozoon,Atoxoplasm,andAegyptianella.Ofthese,onlyHemoproteuswascommonlyseeninwild‐caughtpsittacines,mostlyincockatoos.Microfilariasaremicroscopic,immatureformsoffilarialworms(relatedtoheartwormsindogs)thatarefoundinplasma.Theyhavebeenseeninavarietyofpsittacines,especiallycockatoos.Theadultfilarialwormsareusuallyundetectedandmayoccurintheairsacs,thoracicandabdominalcavities,orjoints.SurgicalremovalofadultwormsandIvomectinarethetreatmentsofchoice.