Studies on the Morphology of Sarcocysts inThoroughbred Horses in Japan

著者（英） Yamada Masaji, Yukawa Masayoshi, SekikawaHiroho, Kenmotsu Minoru, Mochizuki Koshi

journal orpublication title

The journal of protozoology research

volume 3number 1page range 14-19year 1993-01URL http://id.nii.ac.jp/1588/00001696/

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Provided by Obihiro University of Agriculture and Veterinary Medicine Academic Repository

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StudiesontheMorphologyofSarcocystsin

noroughbredHorseshJapan

MASAJIYAMADA一，MASAYOSHIYUKAWAl，HIROHO SEKIKAWA2， MINORU KENMOTSU2and KOSHIMOCHIZUKIl

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Keywords：Thoroughbred，Sarcocystis′CyStWa11′electronmieros亡OPy

A13STRACT From1981to1990，93ThoroughbredinJapanwere examined

forSarcocystiscystsuslnglight／SCanrung and transmission electronmicroscopy・Tryptiedigestionofmuscletissues revealed Sixinfectedhorses・Sarcocystis bradyzoiteswere foundinthe myocardium′maSSeteranddiaphragmmus⊂les・Cysts were elliptical′SPindle or mulberry shaped′meaSurlng77・7－222・0岬I X48・1－111・Opn・Cystwallswerel・0－0・6pmthickandhavea SmOOthsllrfaceinHE－Stained sections・Bradyzoitesranged from 12・0－16・6一皿IX3・0－5・3岬l・Themorphology of cysts revealed many similaritieswithSarcocystisequicanis・NopathologlCal Changeswereobservedininfectedmus⊂1efibers．

INTROl）UCTION Siedamgrotzky（1872）observed for the first time

SarCOSPOridian cystsinmuscletissuesofahorseanddescribed them as sporospermialtubes・Subsequently′DoElein（1901） Observedsimi1arcystsandnameditSarcocystis bertrami．The morphologyofm11ChsmallercystsofSarcocystisequicanis of horses wasinvestigatedbyRommelandGeisel（1975）and by G6bel（1976），thelatterusingelectronmicroseopy・Likewise′ morphologicaldetailsofathirdspecies／Sarcocystisfhyeri，Were WOrked outby Dubeyetal・（1977），andbyTinlingetal．（1980）at the ultrastructurallevel・Thesedo⊂umentedreportstendto SuggeSt that there eouldpossiblybe two orthree different SPedes of Sarcocystisinfectinghorses・Inthepresentstudy′We

ブイ

SARCOCYST IN THOROUCHBRED

soughttoexamineandcharacterize sarcocystsinThoroughbred horsesinJapaT from1981to1990，WiththeuseOfbothlight and electronmlCrOSCOpy・ し－～・－一

MATERIALS AND Mt；THODS Muscles（cardiac，maSSeter′diaphragm，CerVieal′1ingual，

esophagus′andcoccygeal）of93Thoroughbredwhichwere sacriLiced due toinevitablein］uries resultingfroma⊂Cidentsin theNiigatahorseracecourse wereexamined・

Muscletissues were digestedwithO・3％trypslnin phosphate bufferedsaline（PBS）asdescribedbyMaitani（1970）・Mus⊂1e tissues of bradyzoiteTPOSitive horseswere examined forcysts using hematoxylinandeosin（H＆E）stained sFCtionsand SCanningeleetronmicroscopy（SEM）・FortransmisslOn electron microscopy（TEM）eysts Yereisolatedbymacerationofmuscle tissuesinPBS・Afterrinslng theisolated cysts two or three timeswithPl∋S′ theywereprocessedfollowlng TEM routine fixation and stainmg pr∝edures・

RESULTS Sixof93examinedThoroughbred（6・4％）were found to be

infectedwithSarcocystis・Inal1fivehorses，Cardiacmuscles were POSitive for cysts（three casesinvolvingcardiacmusclesonly； OneCaSeinvolving both〔ardiacandmassetermuscles；OneCaSe invoIving both〔ardiacanddiaphragmmuscles）′ andonehorse WaSfoundpositiveinthemassetermuscles only（Tablel）・

Tablel・Sarc∝yStSinThoroughbredsoEdiLLerentages・

Age numberofhorses numbe－ deはtddensity 既amin由 psitive （PSitive％）

5275つJ1

52

45‘U7父U9

＜ ■

エ〓■

Tol且1 93 6 （6．4％）

Numberofbradyzoi随SObseⅣdwithlightmiぐTO父OPyPモー mi⊂rO父Opicfidd（Mg・Xl（MO）＝1－9＝＋；1（ト卵三十十；≧l00＝＋＋十・

．－亨

SARCOCYSTIN THOROUCHlヲRED

謹岩葉酸葦菜聾露

Depending onthe plane of sectionlng and angleof SeCtions′CyStS Were mainly elliptical，SPindle ormulberry Shaped′ranglngin size from77・7－222・Opmx48．1－111．Opm． The thickness ofthe cyst wal1ranged froml・0－0・6pm・Cyst Wal1s exhibitthinandsmoothsurLace dosely adhered tomuscle fibers（Fig・1and2）・Cystsurfaceappeared densely－Stained and Slightly eroded（Fig・3a）・Portionsof cyst wallshow亡1aw－like PrOtruSionandragged－lookingface（Fig・3b）・Betweencyst and muscle tissues′freelydistributedpiecesofprojections which seem to orlglnate from such crustacean claw－1ike protruSions were Observed・Thebase and main parts seenin different planes of SeCtions are shownin Figure 3d・SlightlYStained ground Substance within cyst wa11′and丘ne particulate materialof high electron densityinthemiddlelayerof the wa11with Semitransparentemptyvacuoles were noted・Theinner side of thecystwal1extendedinto the cyst to formseptain closeconta⊂t withbradyzoites（Fig・3c）・

／♂

SARCOCYSTIN THOROUGHBRED

SARCOCYSTIN THOROUGHl】RED

Inside the cysts were proliferative metrocytes and developing and mature bradyzoites（Fig・3E）・liradyzoites measured12・0・16・511mX3・0－5・3LLm and the shapevaries accordingtotheplane of sectionlng・Creseent bradyzoites dominate（Fig・2）whiehclosely resemble apicalcomplexes COmmOn tO an tyPeS Of coccidians（Fig・3e）′and theylie in Closecontaetwiththeinnersideofcystwal1septa・

Within bradyzoites′nuClei，mit∝hondria，micronemes，Golgi apparatus′COnOid and conoidrings′ rhoptries，amylopectin granules，anddouble struCturedpenicleswereobserved（Fig・3a and3f）・Except for some rather thickened sites ofthecystwall′ musdefibersincontact with，andinthevidnity ofthecyst wal1 indicated nopathologlCalehangeswithinZ－lines′andinthe actin andmYOSin丘1aments（Fig・3g）・

DISCUSSION Three different spedes ofSarcocystis have been described

inhorses′S・bertrami，S・equicanis andS・fhyeri（Doflein1901； RommelandGeisel1975；G6bel1976；Dubey1976；Dubeyetal・ 1977；TinlingetalT1980）・However，Dubeyetal，（1977）・have doubtedif these are truly different species′ and thus′ POStulatedthat both′S・equicanis andS・bertrLmiare the same SPeeies as S・fhyeri・Inthe present study，uSing morphological PrOPerties of cysts and cyst walls′ We COmParedour Observationswith those of the described spedes・The cysts of S・equicanis measureabout350トmlong，with thin cystwall measurlngl・5－2・Opm and exhibiting 8－12nm thread－1ike PrOtruSions presentontheoutersurface（G6bel1976）・Anotller Striking feature of thecyst wal1isitsabilitytostainwe11with OSmium tetroxide・WithTEM′Otherauthorshave reportedthe PreSenCe Of thin cyst wall（1essthanl・Opm）withasmooth Surfa亡einsarcocystsinhorses（Boyetal・′1990；HilaliandNassar， 1987；Tinlingetal・，1980）・These observations are simi1ar to the morphologyofS・equlCanis cystwal1asreportedby Rommeland Geisel（1975）・The fine morphologicalstruCtureS Ofthe cYStS notedinthepresent studyresemble moreS・equicLZnis thanany Otherofthedescribed speciesinfectivetohorse・

Itis worth citing that the6・4％infection rate of ThoroughbredwithS・equicanis inJapanwithin thelastlO yearsis signincantlylowereomparedtothe15－30％reportedin

∴、

SARCOCYSTIN THOROUCHBR】∃D

theUSA and Europe（DubeYetal・1989）・This may be partly attributedtotheimprovedajld betterfeeding management of horsesinJapan・

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