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General Characteristics
Flat, unsegmented worms Leaf-like organisms Incomplete digestive tract Oral sucker (nourishment) Ventral sucker or acetabulum
(for attachment)
General Rules
All are hermaphroditic All require two intermediate
hosts Eggs of all trematodes are
operculated The infective stage is
metacercariae
Schistosomes
EXCEPT
Classification of Medically Important Trematodes
Phylum Platyhelminthes Class Trematoda Subclass Digenea
(All trematode parasites of man belong to this subclass, endoparasites with one or more suckers, no chitinous anchors or hooks, complex life cycles with alternating hosts, sexual and asexual reproduction)
Classification
Order: Protostomata Suborder: Strigeata Family: Schistosomatidae Genus: Schistosoma Species: (S. haematobium , S. mansoni, S.
japonicum)S. mekongi, S. intercalatum, S. bovis, S.
matthei
Classification
Order: Protostomata Suborder: Amphistomata Family: Paramphistomatidae Genus: Gastrodiscoides /
Watsonius Species: G. hominis W. watsoni
Classification
Order: Protostomata Suborder: Distomata Family: Fasciolidae Genus: Fasciola Species: F. hepatica F. gigantica Fasciolopsis buski
Classification
Order: Protostomata Suborder: Distomata Family: Opisthorchidae Genus: Clonorchis /
Opisthorchis Species: C. sinensis O. felineus O. viverrini
Classification
Order: Protostomata Suborder: Distomata Family: Heteropyidae Genus: Heterophyes/ Metagonimus/ Haplorchis Species: H. heterophyes M. yokogawai H. taichui H. yokogawai
Classification
Order: Protostomata Suborder: Distomata Family: Troglotremetidae Genus: Paragonimus Species: P. westermani
Classification
Order: Protostomata Suborder: Distomata Family: Echinostomatidae Genus: Echinostoma Species: E. ilocanum
Classification
Order: Protostomata Suborder: Distomata Family: Echinostomatidae Genus: Echinostoma Species: E. ilocanum
Classification of Ova
Mature Schistosoma
OpithorchisClonorchisHeterophyids
Classification of Ova
ImmatureParagonimusFasciolaFasciolopsisEchinostoma
General Life Cycle of Trematodes
Classification Based on Location in Man
A. Species which inhabit the portal bloodstream of vertebrates (Blood Flukes)
1. Schistosoma japonicum - skin penetration of cercaria
- Schistosomiasis japonicum or
Oriental schistosomiasis 2. Schistosoma mansoni3. Schistosoma haematobium
Classification Based on Location in Man
A. Species which inhabit the liver of the vertebrates (Liver Flukes)
1. Fasciola hepatica (Sheep-Liver Fluke)- ingestion of metacercaria on waterplants (Fascioliasis)
2. Clonorchis sinensis (Chinese-Liver Fluke)- ingestion of metacercaria in fish (Clonorchiasis)
Classification Based on Location in Man
A. Species which inhabit the liver of the vertebrates (Liver Flukes)
3. Opisthorchis felineus (Cat liver Fluke)
- ingestion of metacercaria in fish (Opisthorchiasis)
Classification Based on Location in Man
A. Species which inhabit the small intestine of vertebrates (Intestinal Fluke)
Fasciolopsis buski (Giant Intestinal Fluke)
- ingestion of metacercaria on waterplants (Fasciolopsiasis)
Classification Based on Location in Man
A. Species which inhabit the small intestine of vertebrates (Intestinal Fluke)
2. Echinostoma ilocanum- ingestion of metacercaria from
snails (Echinostomiasis)
Classification Based on Location in Man
A. Species which inhabit the small intestine of vertebrates (Intestinal Fluke)
3. Heterophyid Group- ingestion of metacercaria from
fishes (Heterophyidiasis)• H. heterophyes• M. yokogawai• H. taichui• H. yokogawai
Classification Based on Location in Man
A. Species which inhabit Lungs of vertebrates (Lung Flukes)
Paragonimus westermani (Oriental Lung Fluke)
- ingestion of metacercaria from crabs (Paragonimiasis)
Schistosoma japonicum ADULT EGG
M= 12-20 by .5 -.55 mm6-8 ovoid, slighty lobate testis
F= 26 by .3 mm ovary: behind middle of the body in front of intestinal ceca uterus : opens to thhe genital pore just behind the ventral sucker50-100 egg at a time
Ovoidal, 70-100 x 50-65 micraThin and with lateral knob or lateral tubercleMiracidium is present when laid
Schistosoma mansoni ADULT EGG
M= 6-14 x 1.1 mm testis , zigzag row
F = 14 x .25 mm ovary , anterior half of the body uterus : short with 1-3 eggs
155 x 60 micra, S-like curveYellowish with laeteral spineWith miracidium when laid
Schistosoma haematobium ADULT EGG
M = 19-25 x .8-1 mm covered with minute Integumentary tuberculations or fine tubercle long intestinal ceca reunite mid of bodyTestis are in groups : 4-5 , behind the ventral sucker F = 20 x .25 mm suckers:= small, subequal ovary : posteriod half of the body uterus : 20-30 eggs at a time
112 – 170 x 50 micraLight yellowish brown with terminal spineWith miracidum when laid
Comparison of the Schistosome Eggs
Infective Cercariae
Pear-shaped body with rounded end and a long tail and bifid
Thin walled filled with germ cells
Miracidium surrounded with fine- hairlike projections
Snail IH
Fasciola hepatica/Fasciola gigantica ADULT EGG
Large, flat, brwonish3 x 1.5 cmWith OS and VS
Integument covered with scales posterior end surface smooth
Alimentray system inverted Y Branched ceca with lateral branches
Operculated,140-150 x 65-90 micra (hepatica)160-190 x 70-90 micra (gigantica)Light yellow : bile stained
Transparent with thin double wallsContain lecithin granules (immature)
Clonorchis sinensis
ADULT EGG
10-25 x 2-3 mm
Opisthorchis felineus/Opisthorchis viverini
ADULT EGG
Fasciolopsis buski ADULT EGG
Large, broadly ovate and narrow at posterior endDo not have cephalic cone2 -7.5 x .8 – 2 cmAlimentary trat simple and do not branch
Yellowish brown ellipsoidal130-140 x 80-85 micra
With clear thick shell and operculated
Immature when laid
Heterophyids ADULT EGG
Elongate, pyriform and Grayish1 -1.7 x .3 - .4 mmCuticle covered with scale like spinesOS small, VS thick walled and muscular Genital sucker at left posterior border With 2 ovoid testis post. 5th of bodySubglobose ovary ant. of testis Vitellaria with large polygonal follicles in lateral post. end
Minute, operculate, ovoidal, light brown28 -30 x 15 – 17 micraSlight shoulder at the rim ofoperculum and knob at the posterior end
Mature when laid
Echinostoma ilocanum
ADULT EGG
Adult : small, elongate, oval, reddish gray .25 - .65 x .1 - .13 cm ant. Circumoral disc surrounded by crown of 49 -51 spines attenuated posteriorly
Integument : covered with plague-like scalesOS smaller then VS
Paragonimus westermani
ADULT EGG
Paragonimus westermani