Lyme Disease - MSD Manual Professional Edition

Lyme disease is a tick-transmitted infection caused by the spirochete Borrelia species. Early symptoms include an erythema migrans rash, ... MSDManual Pleaseconfirmthatyouareahealthcareprofessional Yes No LeavethisSite? Thelinkyouhaveselectedwilltakeyoutoathird-partywebsite.Wedonotcontrolorhaveresponsibilityforthecontentofanythird-partysite. 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KidneyFailureRiskEquationBestseGFRforPredictingESKD ViewAllNews> ViewAllNews> PROCEDURES ViewAllProcedures> ViewAllProcedures> QUIZZES&CASES Quizzes MoreQuizzes Cases MoreCaseStudies ABOUT Overview History EditorsandtheEditorialProcess PublishingandProductionStaff EditorialBoard Contributors Reviewers ContentProviders GlobalMedicalKnowledge FAQ ContactUs MedicalTopics&Chapters A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Professional / InfectiousDiseases / Spirochetes / ... / LymeDisease / INTHISTOPIC Epidemiology Pathophysiology SymptomsandSigns Early-localizedstage Early-disseminatedstage Late-stagedisease Diagnosis Differentialdiagnosis Diagnosisreferences Treatment Prevention Preventionreference KeyPoints OTHERTOPICSINTHISCHAPTER Spirochetes Bejel,Pinta,andYaws Leptospirosis LymeDisease Rat-BiteFever RelapsingFever ADDITIONALCONTENT Testyourknowledge Toxoplasmosis ToxoplasmosisisinfectionwithToxoplasmagondii.Theonlyknownhostsofthisorganismaredomesticcatsandtheirrelatives.InfectionwithT.gondiiinhumanscanoccurinvariousways.Whichofthefollowingisthemostcommonmodeofinfectioninhumans?   Bloodtransfusion    Ingestionofoocysts    Ingestionoftissuecysts    Transplacentaltransmission   MoreContent Videos 3DModels News SOCIALMEDIA LymeDisease By LarryM.Bush ,MD,FACP,CharlesE.SchmidtCollegeofMedicine,FloridaAtlanticUniversity; MariaT.Vazquez-Pertejo ,MD,FACP,WellingtonRegionalMedicalCenter Lastfullreview/revisionNov2020|ContentlastmodifiedNov2020 ClickhereforPatientEducation TopicResources 3DModels(0) Audios(0) Calculators(0) Images(6) LabTest(1) Tables(2) Videos(1) Ixodesscapularis Deerticks Deertick ErythemaMigrans VariantinErythemaMigrans ErythemaMigransinLymeDisease(Bull'sEyeRash) LymeDiseaseTests GuidelinesforAntibioticTreatmentofLymeDiseaseinAdults* TickBitePrevention OverviewofLymeDisease Lymediseaseisatick-transmittedinfectioncausedbythespirocheteBorreliaspecies.Earlysymptomsincludeanerythemamigransrash,whichmaybefollowedweekstomonthslaterbyneurologic,cardiac,orjointabnormalities.Diagnosisisprimarilyclinicalinearly-stagedisease,butserologictestingcanhelpdiagnosecardiac,neurologic,andrheumatologiccomplicationsthatoccurlaterinthedisease.Treatmentiswithantibioticssuchasdoxycyclineorceftriaxone.Spirochetesaredistinguishedbythehelicalshapeofthebacteria.PathogenicspirochetesincludeTreponema,Leptospira,andBorrelia.BothTreponemaandLeptospiraaretoothintobeseenusingbrightfieldmicroscopybutareclearlyseenusingdarkfieldorphasemicroscopy.Borreliaarethickerandcanalsobestainedandseenusingbrightfieldmicroscopy.EpidemiologyofLymeDiseaseLymediseasewasrecognizedin1976becauseofcloseclusteringofcasesinLyme,Connecticut,andisnowthemostcommonlyreportedtick-borneillnessintheUS.Ithasbeenreportedin49states,but>90%ofcasesoccurfromMainetoVirginiaandinWisconsin,Minnesota,andMichigan.OntheWestCoast,mostcasesoccurinnorthernCaliforniaandOregon.LymediseasealsooccursinEurope,acrosstheformerSovietUnion,andinChinaandJapan.IntheUS,LymediseaseiscausedprimarilybyBorreliaburgdorferiandtoalesserextentbyB.mayonii,whichhasrecentlybeenfoundintheuppermidwesternstates.InEuropeandAsia,LymediseaseiscausedprimarilybyB.afzelii,B.garinii,andB.burgdorferi.Onsetisusuallyinthesummerandearlyfall.Mostpatientsarechildrenandyoungadultslivinginheavilywoodedareas.Lymediseaseistransmittedprimarilyby4Ixodesspeciesworldwide:I.scapularis(thedeertick)inthenortheasternandnorthcentralUSI.pacificusinthewesternUSI.ricinusinEuropeI.persulcatusinAsiaIntheUS,thewhite-footedmouseistheprimaryanimalreservoirforB.burgdorferiandthepreferredhostfornymphalandlarvalformsofthedeertick.DeerarehostsforadultticksbutdonotcarryBorrelia.Othermammals(eg,dogs)canbeincidentalhostsandcandevelopLymedisease.InEurope,largermammalssuchassheeparehostsfortheadulttick.DeertickPathophysiologyofLymeDiseaseB.burgdorferienterstheskinatthesiteofthetickbite.After3to32days,theorganismsmigratelocallyintheskinaroundthebite,spreadviathelymphaticstocauseregionaladenopathyordisseminateinbloodtoorgansorotherskinsites.Initially,aninflammatoryreaction(erythemamigrans)occursbeforesignificantantibodyresponsetoinfection(serologicconversion).SymptomsandSignsofLymeDiseaseLymediseasehas3stages:EarlylocalizedEarlydisseminatedLateTheearlyandlatestagesareusuallyseparatedbyanasymptomaticinterval.ManifestationsofErythemaMigransErythemaMigransErythemamigransisthecharacteristicphysicalfindingofearlyLymedisease.ItbeginsasaredmaculeatthesiteoftheIxodestickbite.Classically,themaculeexpandswithcentralclearing,asinthisimage,but,inmanypatients,nocentralclearingoccurs.Somepatientshavecentralerythemasurroundedbyapalering,andafewdevelopvesicularorulceratedcenters.ImagecourtesyofThomasHabif,MD.VariantinErythemaMigransErythemamigransmaymanifestasarashwithcentralerythemasurroundedbyapalering.LARRYMULVEHILL/SCIENCEPHOTOLIBRARYErythemaMigransinLymeDisease(Bull'sEyeRash)Erythemamigranscanresembleabull'seye,withcentralerythemasurroundedbyapaleringandoutererythematoushalo.CDC/SCIENCEPHOTOLIBRARYEarly-localizedstageErythemamigrans,thehallmarkandbestclinicalindicatorofLymedisease,isthefirstsignofthedisease.Itoccursinatleast75%ofpatients,beginningasaredmaculeorpapuleatthesiteofthetickbite,usuallyontheproximalportionofanextremityorthetrunk(especiallythethigh,buttock,oraxilla),between3daysand32daysafteratickbite.Becauseticknymphsaresosmall,mostpatientsdonotrealizethattheyhavebeenbitten.Theareaexpands,oftenwithclearingbetweenthecenterandperipheryresemblingabull’seye,toadiameter≤50cm.Darkeningerythemamaydevelopinthecenter,whichmaybehottothetouchandindurated.Withouttherapy,erythemamigranstypicallyfadeswithin3to4weeks.Evanescentlesionsmayappearaserythemamigransresolves.Mucosallesionsdonotoccur.Apparentrecurrencesoferythemamigranslesionsaftertreatmentarecausedbyreinfection,ratherthanrelapse,becausethegenotypeidentifiedinthenewlesiondiffersfromthatoftheoriginalinfectingorganism.Early-disseminatedstageSymptomsofearly-disseminateddiseasebegindaysorweeksaftertheappearanceoftheprimarylesion,whenthebacteriaspreadthroughthebody.Soonafteronset,nearlyhalfofuntreatedpatientsdevelopmultiple,usuallysmallerannularsecondaryskinlesionswithoutinduratedcenters.Culturesofbiopsysamplesofthesesecondarylesionshavebeenpositive,indicatingdisseminationofinfection.Patientsalsodevelopamusculoskeletal,flu-likesyndrome,consistingofmalaise,fatigue,chills,fever,headache,stiffneck,myalgias,andarthralgiasthatmaylastforweeks.Becausesymptomsareoftennonspecific,thediagnosisisfrequentlymissediferythemamigransisabsent;ahighindexofsuspicionisrequired.Frankarthritisisrareatthisstage.Lesscommonarebackache,nauseaandvomiting,sorethroat,lymphadenopathy,andsplenomegaly.Symptomsarecharacteristicallyintermittentandchanging,butmalaiseandfatiguemaylingerforweeks.Somepatientsdevelopsymptomsoffibromyalgia.Resolvedskinlesionsmayreappearfaintly,sometimesbeforerecurrentattacksofarthritis,inlate-stagedisease.Neurologicabnormalitiesdevelopinabout15%ofpatientswithinweekstomonthsoferythemamigrans(generallybeforearthritisoccurs),commonlylastformonths,andusuallyresolvecompletely.Mostcommonarelymphocyticmeningitis(cerebrospinalfluid[CSF]pleocytosisofabout100cells/mcL)ormeningoencephalitis,cranialneuritis(especiallyBellpalsyFacialNervePalsyFacialnerve(7thcranialnerve)palsyisoftenidiopathic(formerlycalledBellpalsy).Idiopathicfacialnervepalsyissudden,unilateralperipheralfacialnervepalsy.Symptomsoffacial...readmore,whichmaybebilateral),andsensoryormotorradiculoneuropathies,aloneorincombination.Myocardialabnormalitiesoccurinabout8%ofpatientswithinweeksoferythemamigrans.Theyincludefluctuatingdegreesofatrioventricularblock(1st-degree,Wenckebach,or3rd-degree)and,rarely,myopericarditiswithchestpain,reducedejectionfractions,andcardiomegaly.Late-stagediseaseInuntreatedLymedisease,thelatestagebeginsmonthstoyearsafterinitialinfection.Arthritisdevelopsinabout60%ofpatientswithinseveralmonths,occasionallyupto2years,ofdiseaseonset(asdefinedbyerythemamigrans).Intermittentswellingandpaininafewlargejoints,especiallytheknees,typicallyrecurforseveralyears.Affectedkneescommonlyaremuchmoreswollenthanpainful;theyareoftenhotbutrarelyred.Bakercystsmayformandrupture.Malaise,fatigue,andlow-gradefevermayprecedeoraccompanyarthritisattacks.Inabout10%ofpatients,kneeinvolvementischronic(unremittentfor≥6months).Otherlatefindings(occurringyearsafteronset)includeanantibiotic-sensitiveskinlesion(acrodermatitischronicaatrophicans)andchroniccentralnervoussystemabnormalities,eitherpolyneuropathyorasubtleencephalopathywithmood,memory,andsleepdisorders.Somepatientshavesymptomssuchasfatigue,headache,jointandmuscleaches,andcognitiveproblemsaftersuccessfulantibiotictreatment.Thesesymptomsarecollectivelyreferredtoaspost-treatmentLymediseasesyndrome(PTLDS).AlthoughsomepatientswithsuchsubjectivesymptomsareassignedthediagnosisofchronicLymedisease,thereisnoclearevidencethatsuchanentityexistsorthatthesepatientshaveviableBorreliaremainingintheirbody.DiagnosisofLymeDiseaseClinicalevaluation,supportedbyacuteandconvalescentserologictestingErythemamigransisusuallydiagnosedclinicallybecauseitdevelopsbeforeserologictestsbecomepositive(1DiagnosisreferencesLymediseaseisatick-transmittedinfectioncausedbythespirocheteBorreliaspecies.Earlysymptomsincludeanerythemamigransrash,whichmaybefollowedweekstomonthslaterbyneurologic...readmore,2DiagnosisreferencesLymediseaseisatick-transmittedinfectioncausedbythespirocheteBorreliaspecies.Earlysymptomsincludeanerythemamigransrash,whichmaybefollowedweekstomonthslaterbyneurologic...readmore).Culturesofbloodandrelevantbodyfluids(eg,CSF,jointfluid)maybeobtained,primarilytodiagnoseotherpathogens.Acute(IgM)andconvalescent(IgG)antibodytiters2weeksapartmaybehelpful;positiveenzyme-linkedimmunosorbentassay(C6ELISA)titersshouldbeconfirmedbyasecondenzymeimmunoassay(EIA)orWesternblottest.However,seroconversionmaybelate(eg,>4weeks)oroccasionallyabsent(eg,ifpatientsreceivedpriorantibiotictherapy),andpositiveIgGtitersalonerepresentpreviousexposure.IfonlyIgMbandsaredetectedonWesternblot,especiallylongafterexposure,theresultsareoftenfalsepositive.Polymerasechainreaction(PCR)testingofCSForsynovialfluidisoftenpositivewhenthosesitesareinvolved.Consequently,diagnosisofLymediseasedependsonbothtestresultsandthepresenceoftypicalfindings.AclassicerythemamigransrashstronglysuggestsLymedisease,particularlywhensupportedbyotherelements(eg,recenttickbite,exposuretoendemicarea,typicalsystemicsymptoms).InareaswhereLymediseaseisendemic,manypatientsreportarthralgias,fatigue,difficultyconcentrating,orothernonspecificsymptoms.Fewpatientswhohavethesesymptomsbuthavehadnohistoryoferythemamigransorothersymptomsofearly-localizedorearly-disseminatedLymediseaseactuallyhaveLymedisease.Insuchpatients,elevatedIgGtiters(withnormalIgMtiters)indicatepastexposure,notcurrentorpersistentinfection,andmay,ifmisinterpreted,leadtolongandunnecessarycoursesofantibiotictherapy.ThereisnoevidencelinkingB.burgdorferiinfectiontothisfibromyalgia-likeorchronicfatigue–likesyndrome.DifferentialdiagnosisIntheabsenceofrash,diagnosisismoredifficult.Early-disseminateddiseasemaymimicjuvenileidiopathicarthritisJuvenileIdiopathicArthritis(JIA)Juvenileidiopathicarthritisisagroupofrheumaticdiseasesthatbeginsbyage16.Arthritis,fever,rash,adenopathy,splenomegaly,andiridocyclitisaretypicalofsomeforms.Diagnosis...readmoreinchildrenandreactivearthritisReactiveArthritisReactivearthritisisanacutespondyloarthropathythatoftenseemsprecipitatedbyaninfection,usuallygenitourinaryorgastrointestinal.Commonmanifestationsincludeasymmetricarthritis...readmoreandatypicalrheumatoidarthritisRheumatoidArthritis(RA)Rheumatoidarthritis(RA)isachronicsystemicautoimmunediseasethatprimarilyinvolvesthejoints.RAcausesdamagemediatedbycytokines,chemokines,andmetalloproteases.Characteristically...readmoreinadults.FindingsthatareoftenpresentinrheumatoidarthritisbutnotLymediseaseincludemorningstiffness,subcutaneousnodules,iridocyclitis,mucosallesions,rheumatoidfactor,andantinuclearantibodies.Late-stageLymediseaselacksaxialinvolvement,whichdistinguishesitfromspondyloarthropathiesOverviewofSeronegativeSpondyloarthropathiesSeronegativespondyloarthropathies(seronegativespondyloarthritides)sharecertainclinicalcharacteristics(eg,inflammatorybackpain,uveitis,gastrointestinalsymptoms,rashes).Someare...readmorewithperipheraljointinvolvement.IntheUS,humangranulocyticanaplasmosisEhrlichiosisandAnaplasmosisEhrlichiosisandanaplasmosisarecausedbyrickettsial-likebacteria.EhrlichiosisiscausedmainlybyEhrlichiachaffeensis;anaplasmosisiscausedbyAnaplasmaphagocytophilum.Botharetransmitted...readmore(arickettsialinfection)andbabesiosisBabesiosisBabesiosisisinfectionwithBabesiaspeciesofprotozoa.Infectionscanbeasymptomaticorcauseamalaria-likeillnesswithfeverandhemolyticanemia.Diseaseismostsevereinasplenicpatients...readmoreaswellasBorreliamiyamotoirelapsingfeverandPowassanvirusPowassanvirusArbovirus(arthropod-bornevirus)appliestoanyvirusthatistransmittedtohumansand/orothervertebratesbycertainspeciesofblood-feedingarthropods,chieflyinsects(fliesandmosquitoes)...readmoreencephalitisarealsotransmittedbyI.scapularisandhaveacommongeographicdistributioninthenortheasternandupperMidwest.PatientsillwithanyoneofthediseasestransmittedbyI.scapularismaybeconcurrentlyinfectedwiththeotherdiseasesittransmits.AclinicianshouldsuspectthatpatientswithLymediseasealsohaveBabesiosis(iftheyhavehemolyticanemiaandthrombocytopenia)Humangranulocyticanaplasmosis(iftheyhaveelevatedaminotransferaselevels,leukopenia,inclusionbodiesinneutrophils,and/orthrombocytopenia)AcuterheumaticfeverRheumaticFeverRheumaticfeverisanonsuppurative,acuteinflammatorycomplicationofgroupAstreptococcalpharyngealinfection,causingcombinationsofarthritis,carditis,subcutaneousnodules,erythema...readmoreisconsideredintheoccasionalpatientwithmigratorypolyarthralgiasandeitheranincreasedPRintervalorchorea(asamanifestationofmeningoencephalitis).However,patientswithLymediseaserarelyhaveheartmurmursorevidenceofaprecedingstreptococcalinfection.HumanmonocytotropicehrlichiosisEhrlichiosisandAnaplasmosisEhrlichiosisandanaplasmosisarecausedbyrickettsial-likebacteria.EhrlichiosisiscausedmainlybyEhrlichiachaffeensis;anaplasmosisiscausedbyAnaplasmaphagocytophilum.Botharetransmitted...readmore,whichiscausedbyEhrlichiachaffeensisandtransmittedbyAmblyommaamericanum(theLoneStartick),occursmainlyinthesoutheasternandsouthcentralUSandisunlikelytobeconfusedwithLymedisease.Insouthernandmid-Atlanticstates,bitesfromtheA.americanumtickmayresultinanerythemamigrans–likerashaccompaniedbynonspecificself-limitedsystemicsymptomsandsigns.Nospecificinfectiousagenthasyetbeenidentifiedasthecauseofthisdisorder(calledsoutherntick-associatedrashillness).LymediseasemaycauseBellpalsyand,insummer,canmanifestwithamusculoskeletalasepticmeningitissyndromethatmimicsothercausesoflymphocyticmeningitisorthatmimicsperipheralneuropathies.Diagnosisreferences1.SanchezE,VannierE,WormserGP,etal:Diagnosis,treatment,andpreventionofLymedisease,humangranulocyticanaplasmosis,andbabesiosis:Areview.JAMA315(16):1767–1777,2016.doi:10:1001/jama.2016.22842.BushLM,Vazquez-PertejoMT:Tickborneillness—Lymedisease.DisMon64(5):195–212,2018.doi:10.1016/j.disamonth.2018.01.007TreatmentofLymeDiseaseMultiplealternativesthatvarywithstageofdiseasebuttypicallyincludeamoxicillin,doxycycline,andceftriaxoneMostfeaturesofLymediseaserespondtoantibiotics,buttreatmentofearlydiseaseismostsuccessful.Inlate-stagedisease,antibioticseradicatethebacteria,relievingthearthritisinmostpeople.However,afewgeneticallypredisposedpeoplehavepersistentarthritisevenaftertheinfectionhasbeeneliminatedbecauseofcontinuedinflammation.TableseeTable:GuidelinesforAntibioticTreatmentofLymeDiseaseinAdults*GuidelinesforAntibioticTreatmentofLymeDiseaseinAdults*Lymediseaseisatick-transmittedinfectioncausedbythespirocheteBorreliaspecies.Earlysymptomsincludeanerythemamigransrash,whichmaybefollowedweekstomonthslaterbyneurologic...readmoreshowsadulttreatmentregimensforvariousmanifestationsofLymedisease.Treatmentinchildrenissimilarexceptthatdoxycyclineisavoidedinchildren<8yearsofageanddosesareadjustedbasedonweight(seeTable:UsualDosagesofCommonlyPrescribedAntibiotics[a]UsualDosagesofCommonlyPrescribedAntibiotics[a]Antibacterialdrugsarederivedfrombacteriaormoldsoraresynthesizeddenovo.Technically,“antibiotic”refersonlytoantimicrobialsderivedfrombacteriaormoldsbutisoften(including...readmore).Forsymptomaticrelief,nonsteroidalanti-inflammatorydrugs(NSAIDs)maybeused.Completeheartblockmayrequireatemporarypacemaker.Tensekneejointsduetoeffusionsrequireaspiration.Somegeneticallypredisposedpatientswitharthritisofthekneethatpersistsdespiteantibiotictherapymayrespondtoarthroscopicsynovectomy.TablePreventionofLymeDiseasePrecautionsagainsttickbites(seeTickBitePreventionTickBitePreventionLymediseaseisatick-transmittedinfectioncausedbythespirocheteBorreliaspecies.Earlysymptomsincludeanerythemamigransrash,whichmaybefollowedweekstomonthslaterbyneurologic...readmore)shouldbetakenbypeopleinendemicareas.Deerticknymphs,whichattackhumans,aresmallanddifficulttosee.Onceattachedtotheskin,theygorgeonbloodfordays.TransmissionofB.burgdorferidoesnotusuallyoccuruntiltheinfectedtickhasbeeninplacefor>36hours.Thus,searchingforticksafterpotentialexposureandremovingthempromptlycanhelppreventinfection.TickBitePreventionPreventingtickaccesstoskinincludesStayingonpathsandtrailsTuckingtrousersintobootsorsocksWearinglong-sleevedshirtsApplyingrepellentswithdiethyltoluamide(DEET)toskinsurfacesDEETshouldbeusedcautiouslyinveryyoungchildrenbecausetoxicreactionshavebeenreported.Permethrinonclothingeffectivelykillsticks.Frequentsearchesforticks,particularlyinhairyareasandonchildren,areessentialinendemicareas.Engorgedticksshouldberemovedwithcareandnotcrushedbetweenthefingersbecausecrushingthetickmayresultindiseasetransmission.Thetick’sbodyshouldnotbegraspedorsqueezed.Gradualtractionontheheadwithasmallforcepsdislodgesthetick.Thepointofattachmentshouldbeswabbedwithalcohol.Petroleumjelly,alcohol,litmatches,andotherirritantsarenoteffectivewaystoremoveticksandshouldnotbeused.(SeeHowtoRemoveaTickHowToRemoveaTickTicksshouldberemovedfromtheskintopreventtick-bornedisease(eg,RockyMountainspottedfever,Lymedisease,tularemia,tickparalysis,babesiosis,anaplasmosis,ehrlichiosis,tick-borne...readmore.)Nopracticalmeansareavailabletoridentireareasofticks,buttickpopulationsmaybereducedinendemicareasbycontrollingsmall-animalpopulations.RoutineuseofantibioticprophylaxistopreventLymediseaseafterarecognizedtickbiteisnotrecommended.Patientswithaknowntickbitecaneasilybeinstructedtomonitorthebitesiteandseekcareifrashorothersymptomsoccur;thediagnosticdilemmaofLymeismostprominentwhenthereisnohistoryoftickbite.Asingledoseoforaldoxycycline200mghasbeenshowntoreducethelikelihoodofLymediseaseafteradeertickbite.Accordingtothe2006InfectiousDiseasesSocietyofAmerica(IDSA)guidelines,antibioticprophylaxisshouldbeofferedonlywhenallthefollowingcircumstancesexist(1PreventionreferenceLymediseaseisatick-transmittedinfectioncausedbythespirocheteBorreliaspecies.Earlysymptomsincludeanerythemamigransrash,whichmaybefollowedweekstomonthslaterbyneurologic...readmore):TheattachedtickcanbereliablyidentifiedasanadultornymphalI.scapularistick.Thetickisestimatedtohavebeenattached≥36hours(basedondegreeofengorgementofthetickwithbloodortimeofexposure).Prophylaxiscanbestartedwithin72hoursoftickremoval.(SeeHowtoRemoveaTickHowToRemoveaTickTicksshouldberemovedfromtheskintopreventtick-bornedisease(eg,RockyMountainspottedfever,Lymedisease,tularemia,tickparalysis,babesiosis,anaplasmosis,ehrlichiosis,tick-borne...readmore.)Patientsliveinorhavevisitedanareawhere≥20%oftheseticksareinfectedwithB.burgdorferi(generallyonlyinpartsofNewEngland,partsofthemid-Atlanticstates,andpartsofMinnesotaandWisconsin).Doxycyclineisnotcontraindicated;itiscontraindicatedonlyinpregnantorlactatingwomen,children<8yearsofage,andpeoplewhohavehadanallergicreactiontoatetracyclineantibiotic.Preventionreference1.WormserGP,DattwylerRJ,ShapiroED,etal:Theclinicalassessment,treatment,andpreventionofLymedisease,humangranulocyticanaplasmosis,andbabesiosis:ClinicalpracticeguidelinesbytheInfectiousDiseasesSocietyofAmerica.ClinInfectDis43(9):1089–1134,2006.doi:10.1086/508667.Clarificationandadditionalinformation.ClinInfectDis45(7):941,2007.KeyPointsIntheUS,>90%ofLymediseasecasesoccurfromMainetoVirginiaandinWisconsin,Minnesota,andMichigan;Ixodesscapularis(thedeertick)istheprimaryvectorintheseareas.IntheUS,thewhite-footedmouseistheprimaryanimalreservoirforBorreliaburgdorferiandthepreferredhostfornymphalandlarvalformsofthedeertick;deerarehostsforadultticksbutdonotcarryBorrelia.Lymediseasehas3stages:earlylocalized,earlydisseminated,andlate.Erythemamigransisthefirstandbestclinicalindicator;itoccursin≥75%ofpatients.Inendemicareas,fewpatientswhohavearthralgias,fatigue,difficultyconcentrating,orothernonspecificsymptomsbutwhohavehadnohistoryoferythemamigransorothersymptomsofearly-localizedorearly-disseminatedLymediseaseactuallyhaveLymedisease.Diagnoseclinicallyiftypicalrashispresent;otherwise,doacuteandconvalescentserologictesting(C6ELISAconfirmedbyenzymeimmunoassayorWesternblot).Treatwithoralorparenteralantibioticsdependingondiseasemanifestations. ClickhereforPatientEducation NOTE: ThisistheProfessionalVersion. CONSUMERS: ClickherefortheConsumerVersion ©2021MerckSharp&DohmeCorp.,asubsidiaryofMerck&Co.,Inc.,Kenilworth,NJ,USA Leptospirosis WasThisPageHelpful? Yes No Rat-BiteFever OTHERTOPICSINTHISCHAPTER Spirochetes Bejel,Pinta,andYaws Leptospirosis LymeDisease Rat-BiteFever RelapsingFever Professionalsalsoread AmyotrophicLateralSclerosis(ALS)andOtherMotorNeuronDiseases(MNDs) SubacuteandChronicMeningitis TickBites Testyourknowledge Toxoplasmosis ToxoplasmosisisinfectionwithToxoplasmagondii.Theonlyknownhostsofthisorganismaredomesticcatsandtheirrelatives.InfectionwithT.gondiiinhumanscanoccurinvariousways.Whichofthefollowingisthemostcommonmodeofinfectioninhumans?   Bloodtransfusion    Ingestionofoocysts    Ingestionoftissuecysts    Transplacentaltransmission       MSDandtheMSDManuals Merck&Co.,Inc.,Kenilworth,NJ,USA (knownasMSDoutsideoftheUSandCanada)isaglobalhealthcareleaderworkingtohelptheworldbewell.Fromdevelopingnewtherapiesthattreatandpreventdiseasetohelpingpeopleinneed,wearecommittedtoimprovinghealthandwell-beingaroundtheworld. TheManualwasfirstpublishedin1899asaservicetothecommunity.ThelegacyofthisgreatresourcecontinuesastheMSDManualoutsideoftheUnitedStatesandCanada. LearnmoreaboutourcommitmenttoGlobalMedicalKnowledge. 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