Platyhelminthes or Flatworms ( trematodes & cestodes )

Platyhelminthes or Flatworms are usually dorsoventrally flattened, bilaterally symmetrical and have three body layers lacking a body cavity. They include the trematodes and cestodes.

1. MEDICAL
HELMINTHOLOGY
(PLATYHELMINTHES)
Huda AlislamTalab
B.Sc., M.Sc. Medical Parasitology
University of Medical Sciences and Technology (UMST)

2. •Medicalhelminthologyisthescienceconcernedwith
thestudyofhelminthesorparasiticworms.
•Metazoa(multi-cellularorganisms).

3. Helminthsbelongto2phyla:
1.PhylumPlatyhelminthes(flatworms),Itincludes2classes:
Class–Cestoda(tapeworms)(bodyflattenedandsegmented).
Class–Trematoda(flukes)(bodyflattened,leaf-like,andun-segmented).
2.PhylumNemathelminthes(roundworm)
(elongated,cylindricalwormswithanun-segmentedbody).

4. TREMATODES (FLUKES)
Accordingtothesitestheyinhabittherearefourgroupsof
flukes:
•Bloodflukes dioecious
•Intestinalflukes
•Liverflukes hermaphrodite
•Lungflukes.

5. BLOOD FLUKES
•Theseflukesthatresidemainlyinthebloodvesselsofvarious
organsandtheSchistosomesarethecommonestflukesinour
country.
•The adult parasites worm measure 1-2 cm long.
•The male worm resembles rolled leaf and female is longer & more
slender.
•Normal life span is probably 3-5 years (sometimes live for 30
years).

6. SCHISTOSOMIASIS
(BILHARZIASIS)
•Schistosomeistheonlyflukewithseparatesexes.
•Thefemalewormliesinthegynecophorealcanalofthe
male.

7. Adult male of schistosomaspp.

8. Therearefivemedicallyimportantspecies:
•Schistosomahaematobium:→urinaryschistosomiasis
•Schistosomamansoni
•Schistosomajaponicum
•Schistosomaintercalatum→intestinalschistosomiasis
•Schistosomamekongi

9. Transmission
Presence of the snail
host
Pollution of fresh water with excreta
containing Schistosome eggs
Human
contact
with water
infested
with
cercaria
Snail from genus
Biomphalaria
http://www.cdfound.to.it/H
TML/sch1.htm

10. Requirements for transmission
1.Contamination of water with viable eggs.
2.Presence of water snails.
3.Human exposure to water containing the ineffective stage to
man is the cercaria.

11. Eggs passed in feces or urine

14. •Schistosomiasisistransmittedbycercariaepenetratingtheskin
whenbathing,washingclothes,fishing,orengagedin
agriculturalworkorotheractivityinvolvingcontactwith
contaminatedwater.

15. •S. haematobiumrequires snail of the genus Bulinus.
•S. mansonirequires Biophalaria
S. japonicumrequires Onchomelania.

16. Cercaria in the water
•It is composed of a body 125µm
long by 25 µm in diameter to
which a 200 µm long tail is
attached.
•Swim into the surrounding water
to find their definitive host
•Swims by alternating side-to-side
rhythmic contractions
http://www.personal.leeds.ac.uk/~bgy1mjt/cercaria.
html

17. Cercaria to schistosomula
•Tail is lost
•Shedding of the glycocalyx
•Loss of resistance to the hypoosmolar
stress of fresh water
•Change from aerobic to anaerobic
metabolism

18. Schistosomula
3-4 days in the subdermal layers
Bloodstream briefly passing
through the right side of the heart
into the pulmonary artery
Pulmonary capillaries around the
4th day and remain for 2-3 days
Schistosomulabecomes resistant
to the immune attack
After passing through the lungs
schistosomulacome to rest in the
hepatic portal vein
Antibody dependend cytotoxicity to schistosomulum
http://www.cdfound.to.it/HTML/sch2.htm

19. http://www.nhm.ac.uk/zoology/projects/pr
oject3.html
http://www.med.sc.edu:85/parasitology/schis8.jpg
Schistosome adult
worms
•Male/female pair
copulate throughout
life-produce eggs
•Females resides in
canal-Important for
maturation
•Worm pairs can live
for more than 10
years in a host
•Pair migrate back
against the blood
flow to the
mesenteries around
the intestine.

20. There are three stages of
pathology:
1.Stage of migration and maturation.
2.Egg deposition and release.
3.Tissue reaction to retained eggs.

21. Stage of migrationandmaturation
•Within24hoursofinfectionanintenseirritationandskinrash,
referredtoas‘swimmer’sitch’,mayoccuratthesiteofcercarial
penetration,cellularinfiltrationinlungs,acutehepatitisfever,
urticaria,eosinophilia.
•Thedegreeofillhealthandseriouscomplicationsthatdeveloplater
inlifearerelatedtotheintensityanddurationofinfection.

23. •Migration of the schistosomula: chills, fever, sweating, cough,
diarrhea, leukocytosis
•Acute phase (Katayama diseases by S. japonicum)
•fever, chills, headache, anorexia, urticaria, lymphadenopathy
and diffuse vasculitis lesions
•2-3 weeks after the infection and usually lasts 1-2 months

24. Egg deposition and released:
Eggsescapesfromthebodytoenablethelifecycletobecompleted.
•PassagethroughthebladderandpenetrationinS.haematobium
causesterminalhaematuria,dysuria,frequencyofurinationand
suprapubicpain.
•InS.mansoniandS.japonicumtheeffectoccursinthebowel
givingriseto:abdominalpain,diarrhoeaandbloodinfaeces.
•Pathologyduetoschistosomiasisisaresultofimmunological
responseofthehosttotheparasiteproducts.

27. Tissue reactionto retained eggs
Theseriouseffectsofschistomiasisismainlyduetotissuereaction
toretainedeggs,thedestroyedeggsinduceachronicinflammation
anddevelopmentofgranulomainmanyorgans.
Granulomacharacteristic:epithelioidandgiantcells,lymphocytes,
eosophilsarrangedaroundtheeggs.

28. Inurinaryschistosomiasis:
•ItistheeggsofS.haematobiuminthetissuesnottheadult
flukesthatstimulatehostinflammatoryresponsesthat
resultintheclinicalfeaturesanddamagetothebladderand
ureters.

29. •Eggstrappedinthewallofthebladderandsurroundingtissuescause
inflammatoryreactionswiththeformationofgranulomata.
•S.haematobiumcausessquamouscellcarcinomainthebladder.

30. Inintestinalschistosomiasis.
•Intestinaltractcomplicationsarisingfromchronicinfectionare
causedbyacellularreactiontotheeggsinthetissues.
•Aproportionoftheeggsreachtheliverthroughtheportalvein.
•Intheliver,reactiontotheeggsmayeventuallycausethickeningof
theportalvesselsknownasclaypipe-stemfibrosis.

31. Granuloma of S.mansoni

33. •Prolongedheavyinfectioncanleadtoamarkedenlargementofthe
liver(hepatomegaly)withfibrosisandportalhypertension.
•Thespleenmayalsobecomeenlarged(splenomegaly).
•Deathfromhaematemesiscanoccurfromrupturedoesophageal
varices.

34. Egyptian boy with
hepatosplenomegaly, ascites fluid
build-up and superficial collateral
circulation
(NAMRU-3 clinical ward in Cairo)
‘Intestinal’ asymptomatic
schistosomiasis at the
Egyptian village level
The morbidity spectrum of
schistosomiasis mansoni

35. Collateral circulation

37. Liver Trematodes
1.Clonorchissinensis
•IsknownastheChineseorOrientalliverfluke
•ThenameOpisthorchissinensisisalsoused.
•Theinfectionisreferredtoasclonorchiasis(jaundice,hepatitis,
cirrhosis,andbiliaryobstruction.insomecasescancerofthebile
ductcandevelop).

38. 2.Fasciola hepatica and Fasciola
gigantica
•Fascioliasis(fever,sweating,abdominalpainandinflammationin
thebileducts).
•Withchronicinfectionthereisthickeningofthebileductsduetoa
hostcellularresponse,obstructivejaundiceandthegallbladder
canalsobeinfected.

40. Intestinal trematodes
1.Fasciolopsis buski
•Itisknownasthegiantintestinalfluke.
•Fasciolopsiasis(inflammationandulcerationoftheintestinalwall
withdiarrhea,oedemaofthefaceandlimbsandascites).
•2.Heterophyesheterophyes
•Heavyinfectionscancauseintestinalinflammationandnecrosis.

41. Lung trematodes
Paragonimuswestermani
•Paragonimusflukecauseparagonimiasis,alsoknownaslungfluke
disease.
•Paragonimiasis(pulmonarydiseasewithinflammatoryresponses
totheflukesandegg.
•Symptomsresemblethoseoflikepulmonarytuberculosiswith
chestpain,cough,nightsweats,andhaemoptysis(coughingup
blood).

42. CESTODES (TAPEWORMS)

43. Thebodyisdifferentiatedinto3parts
Scolexorhead:carriestheorgansof
attachmenti.e.suckersorhooks
Neck:unsegmentedactivelygrowingregion
Strobilla:composedofproglottids
(segments),startingbyimmaturesegments
followedbymaturesegmentsandgravid
segmentswhichcontainseggs.

44. Echinococcusgranulosus
(Dwarf dog tapeworm)
•Echinococcusspecies are small tapeworms, and have only a
few (two to six) proglottids
•Echinococcosis is caused by larval tapeworms (hydatid cyst)
•Responsible for most cases of echinococcosis, cystic
disease or Hydatid Disease.

45. Distribution
•Occursworldwide,withrelativehighprevalenceineasternandsouth-
easternEurope,theMediterraneancountries,theNearEast,northernand
easternAfrica,southAmericaandvariouspartsofAsiaandAustralia.
45

46. Morphology
•Theadultwormmeasures3-6mminlength
•Ithasscolex,neckandstrobilla
•Liveinsmallintestineofdefinitivehost(dog)
•Manisanintermediatehost-carryingthehydatidcyst(larva).
46

47. Larval stage
•Hydatid cyst which contain protoscolices, form in the liver,
lung or brain affect their functioning & damaging
surrounding tissue.

49. •Hydatidcystcontainprotoscolices
•Itiscolorless
•Roundtoovalinshape
•Measuringabout140×80Mm
49

50. •Withfocusingthehooksofscolexcanbeeasilyseen
•Viableprotoscolecesdonotstainwitheosin
•Non-viableprotoscolecesstainredwitheosin.
50

51. 51

52. Transmission
•Humansarenotanaturalintermediatehostoftheparasite,butin
rarecasescanbeinfected
Ingestionofeggsbythefollowingways:
•Ingestionofwaterorvegetablespollutedbyinfecteddogfeces.
•Handlingorcaressinginfecteddogswherethehairsareusually
contaminatedwitheggs.

53. Clinical features:
Hydatid disease
•Infection can produce serious
symptomsdepending on the site
and sizeof the hydatid cyst and
host response .

54. 54

55. •Echinococcusgranulosusinfectionsremainsilentforyearsbeforethe
enlargingcystscausesymptomsintheaffectedorgans.
•Hepaticinvolvementcanresultinabdominalpain,amassinthehepatic
area,andbiliaryductobstruction.
•Pulmonaryinvolvementcanproducechestpain,cough,and
haemoptysis.
•Rupture of the cysts can produce fever, eosinophilia, as well as cyst
dissemination.
•Theirpresenceinthebrainmaycauseblindness&epilepsy.
•Inbone,thecystspreadandcausingpainandbonefracture.
•Pressurefromexpandingcyst

56. Diagnosis:
•X-ray or other body scans.
•Serology : testing serum for antibodies produced in response to
infection and testing for cystic antigen

57. Treatment
•Surgery
during surgery, care must be taken
not to puncture a hydatid cyst
because leakage of the fluid can
cause massive reinfection from
released protoscoleces

58. Taeniaspecies
•Taeniasaginataisalargetapewormthatcausesaninfectioncalled
taeniasis,oftenreferredtoasthebeeftapeworm(infectionfrom
eatinginfectedbeef).
•Taeniasoliumastheporktapeworm(infectionisbyeating
infectedpork),causesaninfectioncalledtaeniasisand
cysticercosis.
•Humansarethedefinitivehost.

59. Morphology
•Adultwormmeasures5-10
metersinlength
•Thescolexhas4suckersbutno
hooks

61. •Consistofupto2000segments
•Gravidsegment:appearwhiteand
measuringabout12mmlongby6
mmwide
•Uterushasacentralstemwhich
hasmorethan13mainside
branchesoneachside

64. Taeniasolium
•T.soliumisnotaswidely
distributedasT.saginata,it
occursmainlyinsouthernAfrica,
China,India,centralAmericaand
non-IslamicsouthEastAsia.

65. Morphology
•Adultwormmeasuresabout3
metersinlength.
•Thescolexhassuckersandhooks

66. •Consistof800-1000segments
•Gravidsegmentsappearsgrey-blue
andabout13mmlongby8mmwide
•Uterushascentralstemwhichhasup
to13mainsidebranchesoneachside

67. Morphology of the parasite
Scolex of T.solium Scolex of T.saginata

71. Taeniasis
•Taeniasaginatataeniasisproducesonlymildabdominal
symptoms.
•Themostunusualfeatureconsistsofthepassageofproglottids.
•Appendicitiscanresultfrommigratingproglottids.

72. •TaeniasoliumtaeniasisislessfrequentlysymptomaticthanTaenia
saginatataeniasis.
•Themainsymptomisoftenthepassageofproglottids.
•ThemostimportantfeatureofTaeniasoliumtaeniasisistheriskof
developmentofcysticercosis.

73. •T.soliumcysticercosis:infectionwithlarvaeofT.soliumcan
causecysticnodulesinsubcutaneoustissuesandmuscles.Usually
thelarvaproducefewseriousclinicalsymptomsexceptwhen
presentinthebrainwheretheycancauseepilepsyandother
centralnervoussystemdisorders.

74. Cysticercosisin human muscle

78. H.nana
•ThenameHymenolepisreferstothethinmembranecoveringthe
egg(Greekhymen-membrane,lepis-covering)andnanatoitssmall
size(nanus—dwarf).
•Commonname:Dwarftapeworm.

79. •Hymenolepisnanaisthesmallestandthemostcommontapeworm
foundinthehumanintestine.
•Itisuniquethatitistheonlycestodewhichcompletesitslifecycle
inonehost-humans.
•Commonassociateddiseaseandconditionnames:Hymenolepiasis
ordwarftapewormdisease.

80. Clinical Features
•Thereareusuallynosymptomsbutinheavyinfections,thereis
nausea,anorexia,abdominalpain,diarrhea,andirritability.
•Sometimespruritusmayoccurduetoanallergicresponse.
•Toxinsreleasedfromthewormscancauseallergicreactions.
Severeandsometimesdisseminatedinfectionscanoccurin
malnourishedandimmunosuppressedpersons

81. Hymenolepis diminuta
•Commonname:Rattapeworm.
•Commonassociateddiseaseandconditionnames:
Hymenolepiasis,rattapewormdisease.
81

82. Transmission
•H.diminutaisatapewormnormallyparasiticinrodents,with
fleasandinsectsservingasintermediatehosts.
•Humansbecomeaccidentallyinfectedbyswallowingan
intermediatehost(insectsinfestedwithlarvaeofH.
diminuta).
•Hymenolopiasisoccursmorecommonlyinchildren.

83. Clinical features
•Thesymptomsarerelatedtowormburden;however,inmost
patients(usuallychildren)complaintsmayconsistofindigestion
andappetiteloss.
•Theinfectionmayfirstbenoticedwhenproglottidsmigrate.
•Symptomshavebeenreportedandcanincludeabdominalpain,
diarrhea,andpruritus
•Amoderateeosinophiliamayalsobepresent.
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84. Diphyllobothriumlatum

85. •Known as the fish tapeworm or broad fish tapeworm because its
larvae are found in fish. Humans are the important definitive hosts
•Diphyllobothridaerequire intermediate hosts (fish) to complete their
life-cycle.

87. Transmission
•D.latumistransmittedbyingestingplerocercoids
(infectivelarvae)inraworundercookedfish

88. Life cycle

89. Diphyllobothriasis
•InfectionwithD.latumcancausegastrointestinalsymptoms,
weakness,weightloss,andotherclinicalfeaturesduetotoxins
releasedbythetapeworm.
•Veryoccasionallyamegaloblasticanaemiamaydevelopdueto
theuptakeofvitaminB12bythetapewormincompetitionwith
thehost.

91. Thank you