Common Features of Human Trematodes

1. Common Features of Human Trematodes 1. Most adult trematodes are dorsoventrally flattened, bilaterally 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 cecum 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 small spine (knob). The developed egg contains a miracidium.

2. 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 water 9. 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.

4. Clonorchis 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 archaeologists found this worm in a body from a tomb dating from the second century B.C. in Jiangling,Hubei Province. The Chinese liver fluke is distributed in Asia (Far East region). The infections result from eating raw or half-cooked fresh water fish and shrimps. The worms blocking the bile passages cause clonorchiasis, which finally may become the biliary cirrhosis.

5. I. 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.

6. Adult worm of C. sinensis

8. 2. Egg: looks like a sesame seed under the low power and a water melon seed under the high power. It is yellow brown in color, averages 29×17µ(the smallest helminth egg). The shell is thick and there are an operculum and a small knob on the posterior end. The content is a miracidium. 3. metacercaria is spherical, 0.138 X 0.1mm, in fish muscles.

10. Egg of C. sinensis

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

12. II. 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,  

13. 1st Int. hosts: Bithynia

14. fish of Family Cyprinidae such as pseudorasbora parva 麦穗鱼, Cyprius carpio 鲤鱼, Aristichthys nobilis 大头鱼, Mylopharyngodon piceus 青 鱼.

16. 肝吸虫雷蚴 囊蚴 肝吸虫尾蚴

19. III. Pathology and symptoms Liver 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

20. 肝胆管内肝吸虫（切片）

21. Clinical 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).

22. 肝吸虫病患儿

23. 肝吸虫病患者

24. 类侏儒症型肝吸虫病

25. IV. 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.

26. V. 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

27. VI. Epidemlology The Chinese liver fluke is distributed in Asia (Far East region: China, Japan, Korea, Thailand, Kampuchea, Vietnam, and etc.). In China it is found in 25 provinces, cities and autonomic regions except Xinjiang, Gansu, Inner Mongolia, Qinghai, Ningxia and Tibet. It is widely prevalent in Shandong Province. Epidemiological survey: (1) int hosts (snail, fish, shrimp) (2)reservoir hosts, (3) discovery of patients and carriers, (4) habits of eating raw fish (5) type of growing fish.