Trematodes (Flukes)

1. Trematodes (Flukes) Department of Parasitology, Xiangya Medical School, Central South University

2. General Introduction • Classification and Species • Phylum Platyhelminthes (flatworms) • Class Trematoda • Order Monogenea • Order Aspidogastrea • Order Digenea All trematodes parasitizing human belong to the Order Digenea.

3. General Introduction • Classification and Species Common human trematodes: Clonorchis sinensis (liver flukes) Heterophyes heterophyes Fasciolopsis buski Fasciola heptica Paragonimus westermani Pagumogonimus skrjabini Schistosoma japonicum Echinochasmus japonicus (lung fukes)

4. General Introduction • Important species in China Clonorchis Fasciolopsis Paragonimus Schistosoma sinensis buski westermani japonicum

5. General Introduction • Morphological characteristics 1、Adult worms • flattened, bilaterally symmetric, leaf- shaped or tongue-like • about 0.3-80.0mm in length • two suckers, an oral and a ventral sucker • Most of trematodes are hermaphroditic, except schistosomes • incomplete digestive tract, the caeca end blindly, without anus • Without body cavity (acoelomate)

6. General Introduction • Morphological characteristics 2、Eggs • oval or elliptical • different in size,depending on species • most species have an operculum or cap at one end, apart from schistosomes • In many species the egg contains a fully developed miracidium

7. Introduction to trematode • Characteristics of life cycle • Typical developmental stages: redia sporocyst Ovum(egg) miracidium cercaria metacercaria adult

8. General Introduction • Characteristics of life cycle • Requiring one or two intermediate hosts: 1st intermediate host is usually snail in fresh water, the secondary intermidate host belongs to species of animals in water,such as fishes and crabs

9. General Introduction • Characteristics of life cycle • Alternation of generations: • Asexual generations in the intermediate host • Sexual generations in definitive host • They have their reservoir hosts. The fluke diseases are zoonoses.

10. Clonorchis sinensis (liver fluke) The worms blocking the bile passages cause clonorchiasis, which finally may become the biliary cirrhosis.

11. Discovery • Clonorchis sinensis was named after it was first discovered in the bile passages of a Chinese carpenter in Calcutta, India in 1874 . • Heanley pulished the first record of an endemic area in Guangdong, south China in 1908. • The discovery of Clonorchis eggs in the fecal material from a corpse in the Warring States Period(475-221 B.C.) in 1975, reveal that C.sinensishas been prevalent in China for about 2300 years

12. Morphology 1、Adult worm • slender, lanceolated or sunflower seed-like(10-25mmX 3-5mm) • the oral sucker is slightly larger than the ventral sucker(located at 1/5 of the body) • two deeply branched testes in tandem are located in the posterior third part of the body • hermaphroditic

13. Morphology 2、Egg • the smallest helminth egg (27~35μm X 12~20μm) • yellow-brown • an operculum • small shoulder-like protrusions • a small knob on the abopercular end • a miracidium inside

14. Morphology 3、Other stages Sporocyst Redia Cercaria metacercaria

15. Life Cycle

16. Life Cycle Adults Eggs Miracidum Sporocyst Redia Cercaria Metacercaria Adults Definitive host (Human,cat,dog) 1st intermidate host (snails in fresh water) 2nd intermidate host (fish and shrimp) Definitive host • 7 stages in life cycle: Adult worm, egg,miracidium, sporocyst, redia, cercaria, metacercaria

17. Life Cycle • two intermediate hosts The first intermediatehost: snails Parafossarulus striatulus Alocinma longicornis The second intermediate hosts: • freshwater fish fish of Family Cyprinidae such as pseudorasbora parva (麦穗鱼), Cyprinus carpio(鲤鱼), Aristichthys nobilis(大头鱼), Mylopharyngodon piceus (青 鱼). • shrimps

18. Life Cycle Development in human Infection Stage metacercaria eating raw fish and shrimp with metacercaria Mode

19. Life Cycle Development in human Residence Stage Adults Site Bile ducts Feed Rich mucosal secretions Life span 20-30 years

20. Life Cycle Development in human Discharge Stage Eggs Mode In the feces

21. Pathogenesis • Worms mechanical and chemical trauma stimulating proliferation of inflammatory reaction in the biliary epithelium • The wall of the bile ducts thickened ,fibrous tissue around the bile duct, and worm obstruction cause cholestasis • When bacteria infection occur, cause cholecystitis, cholangeitis, sometimes cholelithiasis happens

22. Pathogenesis • Bile stream blockage also cause necrosis of local hepatic cells and regeneration of damaged tissue. As a result, biliary liver cirrhosis occur • Associate with cholangiocarcinoma and hepatic carcinoma

23. Pathogenesis Infected liver

24. Pathogenesis Histopathological findings of clonorchiasis (hematoxylin and eosin stain). Note the flukes (arrows) within the dilated bile ducts, biliary epithelial hyperplasia (arrowheads), and periductal fibrosis.

25. Clinical Manifestation • Acute symptoms appear when the primary infection is heavy: sudden onset, chill, high fever, slight jaundice, hepatomegaly, eosinophilia, a few patients have splenomegaly, and weeks later, enter chronic stage • Continuous reinfection: cirrhosis and portal hypertension. In children it may cause malnutrition , growth development disturbance, even dwarf

26. Diagnosis • Epidemiologic data: • 1.living in or coming from the endemic area • 2.The history of eating raw or inadequately cooked • freshwater fish and shrimp • Clinical data: • gastrointestinal symptoms, hepatomegaly, • cholangeitis, cholecystitis, etc.

27. Diagnosis • Etiological diagnosis • 1. discovery of eggs in feces • A. Direct smear • B. Concentration methods • 2. Biliary drainage from duodenum • Immunological tests (for reference only) • IHA (Indirect Hemagglutination) • ELISA (Enzyme Linked Immunosorbent Assay)

28. Epidemiology • Distributed in Asia (Far East region: China, Japan, Korea, Thailand, Kampuchea, Vietnam, and etc.) • In China, there are about 10 million infected individuals and it is found in 25 provinces, cities and autonomic regions except Xinjiang, Gansu, Inner Mongolia, Qinghai, Ningxia and Tibet. It is widely prevalent in the Southern China , such as Guangdong ,Guangxi Province and Hong Kong.

29. Epidemiology • The infection is related with the dietary habits andacquired by eating raw, frozen, inadequately cooked, dried, salted, smoked, or pickled freshwater fish,drunken shrimp, that harbor the metacercaria sashimi Drunken shrimps Porridge with raw fish slices

30. Prevention and control • Control of the source of infection: Treat the patients and domestic animal(cats and dogs, etc.) at the same time. A. Praziquantel is the best choice of drug for the therapy • Dose: 15-25mg/kg, three times a day, for 2 days, • the total dose is 90-150mg/kg • B. Another choice of drug is Albendazole

31. Prevention and control • Cut off the route of transmission: • A. Health education • B. Sanitary disposal of the excreta • C. Avoid eating raw or inadequately cooked • freshwater fish and shrimp.

32. Summary How many stages in the life cycle? Adult worm, egg, miracidium, sporocyst, redia, cercariae, metacercaria Which stage is infective stage? And how? Metacercaria; eating (Ingestion ) Which stage inhabit humans? And where? Adults; Bile duck Which stage is primary cause of the disease? Adults Which stage was detected for diagnosis? Egg