1. Trematode

2. Introduction Taxonomic position Phylum platyhelminthes Class Trematoda
Order Digenea

3. Species Reside in Trematodes that have medical importance
Clonorchis sinensis
hepatic bile duct
Fasciolopsis buski
Small intestine
Paragonimus westermani
Lung, subcutaneous, etc.
Schistosoma japonicum
S.mansoni, etc
portal system

4. General features
Leaf-like flattened bodies with no body cavity; with oral and ventral suckers to aid attachment to their hosts

5. General features
The tegument is a syncytial layer equipped with spines and muscles
Digestive system degenerated，with a mouth, enclosed by the oral sucker but no anus. mouth→pharynx →esophagus → two digestive tracts
Hermaphrodite or monoecious except blood flukes (dimorphism) , possessing both male and female reproductive organs, the appearance and position of which are very important taxonomically

6. Reproductive system of trematode
Female: ovary, oviduct, ootype, Mehlis’ gland, seminal receptacle, Laurer’s canal, vitellaria, vitelline duct, & uterus
Male: testis, vas efferens, seminal vesicale, cirrus,&cirrus pouch

7. Life cycle is complicated – indirect life cycle
General features
Life cycle is complicated – indirect life cycle
Usually need one or two intermediate host –
bio-helmiths
The first intermediate hosts are usually fresh water snails

8. General features Asexual phase:
Eggs can only develop (hatch) in the fresh water
Asexual phase:
Eggsmiracidium in watersporocyst in snail redia cercaria release in water encysted metacercaria in second intermediate host – infective stage
Sexual phase
Preadult (Juvenile)migrated to favorable residing site  adult worm  lay eggs
egg
miracidium
sporocyst
redia
cercaria
metacercaria

9. Egg has operculum except blood fluke
General features
Encysted metacercaria is usually the infective stage (Schistosoma-- cercaria)
Egg has operculum except blood fluke
Features reflecting adaptation to parasitism
Organs of attachment developed
Retardation of digestive system
Highly developed reproductive system

10. Clonorchis sinensis (liver fluke,肝吸虫)

11. Introduction
found from the biliary passage of a Chinese in Calcutta, India in 1874 firstly.
Clonorchis sinensis is known as the oriental or Chinese liver fluke because it is distributed throughout Japan, Korea, China and Vietnam
It is estimated that there are more than 30,000,000 humans getting infection in these areas

12. It is a food-borne pathogen, causes clonorchiasis
The parasite also infects a number of other animals, including dogs, cats, pigs, and rodents, and these animals serve as reservoirs of infection --- zoonosis

13. Morphology
Adult: cm, flat, size and shape like the seed of sunflower
With oral sucker and ventral sucker
The two testes of the male productive organ are branched

14. Sucker & spine
Younger worm

15. pharynx
oral sucker
vitellaria
digestive tract
ventral sucker
uterus
Seminal receptacle
ovary
Excretory bladder
Testis
ceca

16. Eggs Average 29×17µm, yellow brown The smallest helminth egg
Light bulb shape which also looks like sesame or water melon seeds
Operculum with distinctive shoulders
Spine or knob on posterior end
Contains miracidium when discharged

17. well-developed miracidium
operculum
shoulders
spine/knob
well-developed miracidium

18. cercaria
metacercaria

19. Life cycle

20. Life cycle
Need two intermediate hosts
1st intermediate host: fresh water snails, miracidium developed to cercaria in intestine
2nd intermediate host: fresh water fishes or shrimps, cercaria to metacercaria in muscles
Infective stage: metacercaria
Infective route: oral consumption of infective stage
Definitive host: human being
Reservoir host: dogs, cats -- zoonosis
Lodging site: hepatic bile duct

21. 1st intermediate host: fresh water snails
Parafossarulus striatulus
Alocinma longicornis
Bithynia fuchsianus

22. 2nd intermediate host: fresh water fishes and shrimps
Minnows or carps

23. Pathogenesis Stage responsible for the pathogenesis: adult worm
Mechanical irritation – suckers
Toxic effects – excretions, secretions, metabolites
Biological interference – nutrition deprivation

24. Pathogenesis
Invasion of biliary epithelium inflammation  cell infiltration and proliferation  thickening of the duct wall  occlusion  extensive involvement  fibrosis of the liver  hepatocirrhosis

25. Adult worm in hepatic bile duct

26. rabbit infected with Clonorchis sinensis shows fibrosis of the bile duct

27. rabbit infected with Clonorchis sinensis shows hepatocirrhosis

28. hepatocirrhosis

29. Clinical features Asymptomatic to heavy bile duct diseases
Hepatomegaly, jaundice, pancreatitis, bile duct stones, biliary cancer
Maximum worm burden report >70,000 worms
In child, symptoms are usually more serious, could also show malnutrition, nanoid, anemia and sometime causes death

30. Clonorchiasis patients
Clinical features
Enlargement of liver and spleen

31. Clonorchiasis patients
Clinical features
Clonorchiasis patients
Hepatocirrhosis with ascites nanoid kid

32. Diagnosis History of eating raw fish or shrimps Etiological exams
Kato-Katz method
Sedimentation method is the choice for fecal or duodenal aspiration examination if egg burden is low
Immunological diagnosis
ELISA for specific antibodies or circulating antigens

33. Epidemiology and control
Distributed in the Far East including China, Korea, Japan, Vietnam and far east part of Russia
In china, it covers 25 provinces with the highest prevalence in Guangdong (5,000,000 cases), totally 10,000,000 reported cases over the country in year 2003 survey
Dietary habit is the hard part for the disease control

34. Epidemiology and control
Factors associated with endemic:
Existence patients and reservoir hosts (cats & dogs)
Presence of first & second intermediate hosts in the same water body
Mode of fish breeding
Dining habit and custom

36. Epidemiology and control
Control measurements:
Hygiene education – avoid eating raw or undercooked freshwater fishes; separate the raw and cooked food preparation area
Protect fish pond from being contaminated by the feces
Control of reservoir hosts – pets at home, no raw fresh-water fish for cats
Cure patients and carriers – Praziquantel (drug of first choice), 25mg/kg，tid×3d