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Trematodes

Department of ParasitologyDalian Medical University

Ren Yixin

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8 lessons

6 lessonsTrematodes

2 lessonsCestodes

areview

Clonorchis sinensisParagonimus westermani

Fasciolopsis buskiSchistosoma japonicum

Teania soliumTeania saginata

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• Trematode • Cestode

suckers

ribbonlike

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common names

• Clonorchis sinensis: Chinese liver fluke• Paragonimus westermani: lung fluke• Fasciolopsis buski: intestine fluke• Schistosoma japonicum: blood fluke• Teania solium: pork tapeworm• Teania saginata: beef tapeworm

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Common characters of Trematodes

Morphous Life cycle

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Introduction to Trematoda

digenetic trematodes

Leaf-shaped or elongate flat body, resistant cuticle, bilaterally symmetrical without body cavity 2 suckers oral sucker ventral sucker

Monoecism male and female reproductive

system are in the same body

attachmentlocomotion

Morphology of Adult Schistosoma

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Trematode Digestive Tract

Simple mouth

pharynx

esophagus

intestine

Anus absent

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Male reproductive system

two testis

vas efferens 输出管 vas deferens 输精管

Seminal vesicle 储精囊

prostatic gland 前列腺

ejaculatory duct 射精管

cirrus 阴茎

cirrus pouch 阴茎袋

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Female reproductive system

Ovary 卵巢 Oviduct 输卵管Ootype 卵模Mehlis gland 梅氏腺Seminal receptacle 受精囊Laurer’s canal 劳氏管Vitellaria 卵黄腺Vitelline duct 卵黄管Vitelline reservior 卵黄囊 （ vitelline glands ）Uterus 子宫

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Eggs

liver fluke's egglung fluke's egg

intestine fluke's egg blood fluke's egg

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Life cycle:

several development stages of a fluke

Adult eggs miracidium sporocyst

Adolescaria metacercaria cercaria redia

童虫 囊蚴

毛蚴 胞蚴

雷蚴

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cercariasporocyst

metacercaria

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One or two intermediate hosts are required :

First intermediate host is snail

second intermediate host is fresh water fish (clonorchis sinensis)

second intermediate host is crab, crayfish (Paragonimus)

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*Characters of life cycle*

• The trematodes are biohelminths, they need 1 or 2 intermediate hosts, the first intermediate host is mainly fresh water snail.

• Asexual reproduction occurs in the larval stages, sexual reproduction occurs in the adult stage.

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Clonorchis sinensis 华支睾吸虫

Chinese liver fluke

Disease is Clonorchiasis

In China: more than 1.2×107

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The Chinese liver fluke, the The Chinese liver fluke, the trematode trematode Clonorchis Clonorchis sinensissinensis

discovered in the bile discovered in the bile passage of a Chinese at passage of a Chinese at autopsy in Calcutta, India in autopsy in Calcutta, India in 1875 firstly1875 firstly

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Morphology

Life cycle

Pathogenesis & clinical manifestation

Diagnosis

Epidemiology

Prevention & treatment

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Morphology of Clonorchis sinensis

Adult : elongate, narrow, 10-25 mm long,3-5mm wide.

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oral sucker pharynx

ceca

Acetabulumventral sucker

genital pore

Seminal receptacle

uterus

ovary

Testis

esophagus

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Morphology of Clonorchis sinensis

Egg: the smallest

29 ×17µm

operculum

Tiny knob

eggshell

broad rim ("sh

oulder")

miracidium

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Life cycle of C.sinensis

egg miracidium sporocyst redia

cercariametacercarialarva

redia cercaria metacercaria

adult

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Life cycles

parafossarulus

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cercaria

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metacercariae

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First intermediate hosts

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Second intermediate host

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• The patholgical consequences of C.sinensis occur mainly in intra-liver secondary bile ducts. The ultimate effect depends on the intensity and duration of the infection.

• burdens usually small (20-200)

Pathogenesis

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Pathogenesis

Worm in bile ducts

Mechanical irritation

Toxic substances

Erosion of epithelium

Proliferation in biliary epithelium

Bile retention, fibrosis,cancer

Left lobe is mostly involved

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Two adult worms (arrow) in the ductal lumen

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Pathogenesis

extreme thickening of the bile duct (epithelium proliferate).

fibrosis

* Cholangitis

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White areas show cirrhosis in infected liver

* Cirrhosis of liver

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Other symptoms:

Jaundice

upper abdominal distress

diarrhea

hepatomegaly

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Epidemiology

• source of infection

• route of transmission

• susceptible population

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•Source of C.sinensis infection:

Infected human

Infected livestock

Infected wild animals

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Epidemiology

Fish ponds where both snails and fish are present.

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Epidemiology

raw fish is considered a delicacy

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Epidemiology

Human is infected by eating

raw, undercooked, frozen,

dried, salted, smoked fish.

Metacercariae in fish can

withstand salting, smoking,

frozen and drying.

 second intermediate hosts

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Epidemiology

Definitive host: Human

Reservoir hosts: dogs, cats and rats

First and second intermediate host

Way of acquiring: eating raw fish with metacercariae

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Diagnosis

small with operculum

at constricted end

broad rim

tiny knob

卵 盖

Detection of the characteristic eggs in stool or in bile or fluid obtained from duodenum

Associate the history of eating raw fish

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Prevention: safe consumption of infective fish proper sanitation control of human feces. control of the snail and the

reservoir hosts

The drug of choice is praziquantel 吡喹酮

75 mg/kg, divided 3 doses one day, 2-3days

Treatment of Clonorchis sinensis