Common Features of Human TrematodesCommon Features of Human Trematodes

1. Most adult trematodes are dorsoventrally flattened, bilaterall

y symmetric, leaf-shaped or tongue-like.

2. All of them have two suckers, an oral and a ventral sucker.

3. The digestive tract is degenerate. The end of intestine is a ce

cum without anus.

4. The reproductive system is developed and hermaphroditic.

5. Excretory system includes flame cells, capillaries, collecting

tubules and an excretory bladder.

6. Eggs of most species have an operculum (lid, 盖 ) and/or a s

mall spine (knob). The developed egg contains a miracidium.

7. They are biohelminths. Only getting into fresh water can eggs develop. Their intermediate hosts are in water. 1st intermediate hosts are all snails and 2nd intermediate hosts varies from species.

8 Alternation of generations is present in their life cycles. Sexual reproduction get into fresh water9. Life cycle model: adult eggs

lay hatch out

asexual reproduction miracidia 毛蚴 sporocysts 胞蚴 rediae 雷蚴

cercariae 尾蚴 metacercariae 囊蚴10. Infetive stage is usually a metacercria

11. They have their reservoir hosts. The fluke diseases are zoonoses.

Clonorchis sinensisClonorchis sinensis Clonorchis sinensis was named after that the worm

was discovered in the bile duct of a Chinese carpenter in

Calcutta, a harbor city of India, in 1874. our archaeolog

ists found this worm in a body from a tomb dating from

the second century B.C. in Jiangling,Hubei Province. T

he Chinese liver fluke is distributed in Asia (Far East re

gion). The infections result from eating raw or half-cook

ed fresh water fish and shrimps. The worms blocking th

e bile passages cause clonorchiasis, which finally may be

come the biliary cirrhosis.

I. morphologyI. morphology 1. Adult: (1) sunflower seed-like; (2) measuring

10-25 × 3-5mm; (3) the oral sucker at the top is slightly larger than the ventral sucker located in the anterior 1/5 part of the body; (4) reproductive system is hermaphroditic; genital pore is in front of the acetabulum; two deeply branched testes in tandem are located in the posterior third part of the body; the ovary, oviduct, uterus are in the mid part; vitelline glands are in the lateral fields; (5) the digestive tract is divided into two ceca; (6) the pouch-liked excretory bladder opens at the posterior end.

Adult worm of C. sinensis

2. Egg: looks like a sesame seed under the l

ow power and a water melon seed under the hi

gh power. It is yellow brown in color, averages

29×17µ (the smallest helminth egg). The shell i

s thick and there are an operculum and a smal

l knob on the posterior end. The content is a m

iracidium.

3. metacercaria is spherical, 0.138 X 0.1mm,

in fish muscles.

Egg of C. sinensis

Clonorchis sinensis egg. The operculum is visible on one end. Clonorchis sinensis egg. The operculum is visible on one end. The surface of the egg is covered with a wrinkled membrane, The surface of the egg is covered with a wrinkled membrane, giving it an appearance of melon skin. Scanning electron giving it an appearance of melon skin. Scanning electron micrograph. ×3000 micrograph. ×3000

II. Life CycleII. Life Cycle 1. Infective stage: metacercaria;

2. Infective route and mode: eating raw fresh water fish and

shrimps with metacercariae;

3. Site of inhabitation: bile ducts;

4. Biohelnimth: 1st Int. hosts: Bithynia snail; 2nd int. hosts:

fish of Family Cyprinidae such as pseudorasbora parva

麦穗鱼 , Cyprius carpio 鲤鱼 , Aristichthys nobilis 大头鱼 , Mylopharyngodon piceus 青 鱼 .

5. Reservoir hosts: Cat, dog;

6. Life span: 20-30 years,

1st Int. hosts: Bithynia1st Int. hosts: Bithynia

fish of Family Cyprinidaefish of Family Cyprinidae such as pseudorasbora parsuch as pseudorasbora parva va 麦穗鱼麦穗鱼 , Cyprius carpio , Cyprius carpio 鲤鱼鲤鱼 , Aristichthys nobilis , Aristichthys nobilis 大头鱼大头鱼 , Mylopharyngodon , Mylopharyngodon piceus piceus 青 鱼青 鱼 ..

肝吸虫尾蚴

肝吸虫雷蚴

囊蚴

III. Pathology and symptomsIII. Pathology and symptomsLiver flukes live in bile passages (mechanical and chemical irritations)

  Inflammation and proliferation of biliary epithelium

Fibrosis of the passage wall and mechanical obstruction due to worms

Bile stream blockage 

High pressure in bile ducts bacterial infection Cholangitis( 胆管炎） Enlargement of bile duct Cholecystitis （胆囊炎） cholelithiasis （胆石症） Bile secretion stops

Bile is stored increasingly in hepatic Cells and diffuses between them Degeneration of local hepatic cells Necrosis of local hepatiec cells Regeneration of damaged tissue Biliary cirrhosis( the liver gets hard and green)

Portal v. hypertension function failure liver cancer

Ascites, splenomegaly, anemia, coma die

肝胆管内肝吸虫（切片）肝胆管内肝吸虫（切片）

Clinical manifestationClinical manifestation

(1) Light infection: no symptoms

(2) General case: poor appetite, fullness in abdomen, diarrhea, physical weakness, hepatic pain, hepatomegaly.

(3) Severe case: icterus (jaundice), systemic toxemia, chill, fever, vomiting, vertigo, mental disorder, emaciation, ascites. The patients die of coma, infective complications, hemorrhage of upper part of digestive tract.

(4) In child case: physical and mental growths are retarded (dwarf).

肝吸虫病患儿

肝吸虫病患者

类侏儒症型肝吸虫病

类侏儒症型肝吸虫病

IV. DiagnosisIV. Diagnosis

Symptoms + signs + experience of eating raw fish and shrimp +discovery of liver fluke egg

Stool examination:

* 1. alkali digestive method (NaOH10%)

2. Water sedimentation method

3. Direct fecal smear

*4. Duodenal aspiration (drainage)

5. lmmunologic tests are for reference only.

V. Treatment and PreventionV. Treatment and Prevention 1. Drug of choice is praziqantel ( 吡喹酮 ).

Other effective drugs include hexachloroparaxylol （六氯对二甲苯）， bithionol ( 硫双二氯酚或别丁 bitin).

2. Prevention (1) Health education (2) Sanitary disposal of night soil. (3) Avoid eating raw fish and shrimps. (4) Treat and control reservoir hosts

VI. EpidemlologyVI. Epidemlology

The Chinese liver fluke is distributed in Asia (Far East re

gion: China, Japan, Korea, Thailand, Kampuchea, Vietnam, a

nd etc.). In China it is found in 25 provinces, cities and auton

omic regions except Xinjiang, Gansu, Inner Mongolia, Qingh

ai, Ningxia and Tibet. It is widely prevalent in Shandong Pro

vince.

Epidemiological survey: (1) int hosts (snail, fish, shrimp)

(2)reservoir hosts, (3) discovery of patients and carriers, (4) h

abits of eating raw fish (5) type of growing fish.