Medical Microbiology

Babesia

Causativeagentofbabesiosis

BabesiaspeciesareapicomplexanbloodparasitesoftheorderPiroplasmidathat

occurquitefrequentlyindomesticandwildanimalsincountriesonallcontinents

andaretransmittedbyhardtickspecies.Invertebratehosts,theyparasitizeinery-

throcytesandaredetectableinstainedbloodsmears,usuallyintheformofsmall

ringsandsingleordoublepearshapedorganisms(about 2 – 2.5lmlong).Incon-

trasttoplasmodiatheydonotcontainpigment(hemozoin).Babesiainfectionsare

infrequentlyobservedinhumans,primarilyaffectingsplenectomized,elderly,and

immunocompromisedpatients.ThecausativeagentswereidentifiedasBabesiami-

crotifromrodents,B.divergensfromcattle,andsomepreviouslyunknownBabesia

speciesorstrains.Suchinfectionscancauseseveremalarialikesymptoms.

Microspora

Causativeagentsofmicrosporosis

&Theclinicalsignificanceofthemicrosporaisbasedmainlyontheirroleas

“opportunisticparasites”inHIVpatients.Themostimportantspeciesare

EnterocytozoonbieneusiandEncephalitozoonintestinalis.Transmissionis

bycharacteristicspores.Littleisknownabouttheepidemiologyofthese

organismsthatarecloselyrelatedtothefungi. &

Parasites.ThephylumMicrosporaincludesabout 140 generaand 1300 spe-

cies.Theyareparasiteswithintracellulardevelopmentandsporeformation.

Thehostspectrumrangesfromnumerousinvertebrates(e.g.,protozoa,in-

sects)tomanyspeciesinallclassesofvertebrates.Thelackofmitochondria,

peroxisomes,andtypicalGolgimembranesaswellastheirprokaryotelike

ribosomeswerepreviouslyregardedascharacteristicsofmostprimitive

eukaryotes.Recently,analyzesofavarietyofgenesandproteinshavere-

vealedacloserelationshiptofungi.Therefore,someauthoritiesnowconsider

theMicrosporatobehighlyspecializedfungiratherthanprimitiveprotozoa

andplacethemasasuperclassintothesubphylumfungi.Anotablecharac-

teristicofthemicrosporaistheuniquemorphologyoftheirspores(seebe-

low).

Microspora,knownsincethemiddleofthelastcentury,haveattained

attentionashumanpathogensandopportunisticparasitesinthecourseof

theAIDSepidemic.Severalgeneraandspecieshavebeenidentifiedin

humanstodate(Table9. 1 ,p. 47 7).

538 9 Protozoa

9

Kayser, Medical Microbiology © 2005 Thieme