Medical Microbiology

DNAViruses 421

theintercellularspace,thusremainingbeyondthereachoftheimmune

defenses.Possiblecomplicationsincludekeratoconjunctivitisandahighly

lethalformofencephalitis.

TheinitialinfectionwithHSVtype 2 normallyaffectstheurogenitalarea

(“genitaltype”)andcanbecontracteddespiteanexistingHSVtype 1 infec-

tion.HSVtype 2 persistsinthelatentstateinthelumbosacralgangliaorper-

ipheraltissues,fromwhereitcausesepisodesofmanifestherpesgenitalis.

NeurologicalcomplicationsareveryrareandmorebenignthaninHSV

type 1 .Ontheotherhand,infectionsofnewbornchildren(herpesneonator-

um),e.g.,incasesofmaternalgenitalherpes,arefearedfortheirhighlethality

rate.

Diagnosis.Cultivatingthepathogenfrompustulecontentsisthemethodof

choiceinlabialandgenitalherpes.InanHSVencephalitis,thecerebrospinal

fluidwillcontainfewvirusesornoneatall.Insuchcases,theycanonlybe

cultivatedfromtissues(biopsyorautopsymaterial).Virusdetectionby

meansofcerebrospinalfluidPCRisworthatry.

Directdetectionofthevirusesunderanelectronmicroscopeisonlyprac-

ticableifthespecimencontainslargenumbersofviruses,whichinpractice

willnormallyonlybethecaseinblistercontents.Theviruscanalsobede-

tecteddirectlyinpatientspecimensusingimmunofluorescenceorin-situ

hybridization(p.408),butthematerialmustcontainvirus-infectedcells,

i.e.,blistercontentsarenotassuitablehereasinelectronmicroscopyand

virusisolation.

SerologicalinvestigationresultsinHSVlacksignificanceduetothehigh

levelofgeneralcontaminationinthepopulation.

Epidemiology,prevention,andtherapy.HSVtype 1 istransmittedby

contact,andpossiblybysmearinfectionaswell.ContaminationwithHSV

thereforebeginsinearlychildhood.TransmissionofHSVtype 2 usuallyoc-

cursduringsexualintercourse,sothatinfectionsaregenerallynotobserved

untilafterpuberty.Noimmuneprophylaxis(vaccination)iscurrentlyavail-

ableforHSV.Acycloguanosineisusedprophylacticallyinimmunosuppressed

patients(seeChapter 7 ,p. 40 4).

Specifictherapyispossiblewithacycloguanosine.Usedintime,thische-

motherapycansavelivesinHSVencephalitis.

Varicella-zosterVirus(VZV)

Pathogen,pathogenesis,clinicalpicture.TheVZvirusdifferssubstantially

fromHSV,bothserologicallyandinmanybiologicaltraits.Forinstance,itcan

onlybegrowninprimatecellcultures,inwhichitgrowsmuchmoreslowly

andmorecell-associatedthanisthecasewithHSV.Nosubtypeshavebeen

described.

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Kayser, Medical Microbiology © 2005 Thieme