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