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Introduction to tromatodes Phylum Platyhelminthes Class Trematoda Order Digenea.

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Presentation on theme: "Introduction to tromatodes Phylum Platyhelminthes Class Trematoda Order Digenea."— Presentation transcript:

1 Introduction to tromatodes Phylum Platyhelminthes Class Trematoda Order Digenea

2 Morphology Adult worm –Flattened (flatworm) and leaf like –Sucker: oral & ventral (fluke) –Body wall: musculo-tegumental sac –Parenchyma (structure between body wall and internal organs): connective tissue fibers, cells and space between them


4 –Digestive tract: not intact i.e. no anal opening, caecum –Reproductive system: hermaphrodite (monoecious) exception of schistosome –Muscular system –Nervous system –Excretory system

5 Egg –Size divergent –Ovoid –Operculum (exception of that of schistosome) –Content: ovum, vitelline cells, or miracidium

6 Egg of Clonorchis sinensis

7 Egg of Paragonimus westermani

8 Egg of Fasciolopsis buski

9 S. japonicum S. Mansoni S. haematobium Schistosome egg

10 Features Reflecting Adaptation to Parasitism Organs of attachment highly developed Retardation of digestive system Highly developed reproductive system

11 Life Cycle Complex Alteration of generation sexual generation and asexual generation alter in the life cycle of parasite Asexual multiplication in larval stage in snail host Multiple hosts transfer and having reservoir hosts in majority Water environment is essential

12 Important Species Liver fluke: Clonorchis sinensis Intestinal fluke: Fasciolopsis buski Lung fluke: Paragonimous westermani P. skrjabini Blood fluke: Schistosoma spp.

13 The Liver Fluke 肝吸虫 Clonorchis sinensis 中华支睾吸虫

14 Introduction Parasite of biliary passage Cause “clonorchiasis” A common trematode in Far East First report 1874 oversea Chinese in India

15 Morphology Adult worm –Size & Shape like the seed of sunflower –Sucker: oral = ventral –2 dendritic testes lie in tandem to each other in the posterior region (clonorchis)

16 Adults of Clonorchis sinensis



19 Cross section of Clonorchis sinensis adult in the hepatic bile duct

20 Egg –Size: smallest –Shape: just like sesame –Color: yellowish brown –Operculum distinct: shoulder, knob –Content: miracidium

21 Clonorchis sinensis egg. These are small operculated eggs. Size 27 to 35 µ m by 11 to 20 µ m. The operculum, at the smaller end of the egg, is convex and rests on a visible "shoulder". At the opposite (larger, abopercular) end, a small knob or hooklike protrusion is often visible (as is the case here). The miracidium is visible inside the egg.

22 Egg of Clonorchis sinensis

23 Life cycle of Clonorchis sinensis

24 Life Cycle A model pattern of trematode Main points –Definitive host: human being –Reservoir host: dog, cat, etc. –Residing: hepatic bile duct –Discharge of eggs with feces

25 –Hatching in the host small intestine –2 intermediate host I: snails, such as Bithynia,Parafossarulus II: freshwater fishes, such as Cyprinus –2 generation of asexual proliferation –Infective stage: metacercaria in fish –Infective route: oral consumption

26 Pathogenesis Due to adult worm Mechanism –Mechanical: sucker –Chemical: excretions, secretions, metabolite –Biological: nutrition deprivation

27 Pathological process –Inflammation  Proliferation  Thickening  Occlusion –Extensive involvement  Fibrosis of the liver

28 Clinical Manifestations Acute stage: allergic reaction Chronic stage: functional impairment of liver (Cholangitis, Cholecystitis, Bile stone, Jaundice, etc) Advanced stage: portal cirrhosis & malignancy

29 Laboratory Diagnosis Etiological –Examination of egg in feces by sedimentation method –Duodenal aspiration Immunological –ELISA to detect antiboby or antigen

30 Epidemiology Distribution –Far East (China, South Korea, Japan, etc.) –24 provinces in China (Guangdon: 5 million infected etc.)


32 Endemic Factors Source of infection: mainly wild carnivores I,II intermediate host in the same water- field Mode of fish breeding Dinning habit & Customs

33 Principle of Control Cure patients & carrier praziquantel:25mg/kg, tid, 2 days Control reservoir host Carry out scientific fish-breeding Hygienic education not eating raw or undercooked fishes

34 Paragonimus westermani 卫氏并殖吸虫 Paragonimus skrjabini (Paragonimus szechuanensis) 斯氏狸殖吸虫

35 The Lung Fluke Genus paragonimus Zoonotic parasite (cause zoonosis) Animal infection> human infection 2 major species in China

36 Introduction Pathogen of lung disease Endemic hemoptysis Favorite lodging site: lung Ectopic site: brain, abdomen, muscle, etc.

37 Morphology Adult worm Body thick (a half piece of a bean grain) Tegument: spinous Sucker: oral = ventral Parallel arrangement of reproductive organ lobular testes (posterior) lobular ovary & uterus (anterior)


39 Cross section of lung containing adult Paragonimus westermani.

40 Egg –Median size, ovoid (water pot) –Golden yellow –Distinctive & wide operculum –Contain 1 germ cell & several yolk cells

41 Egg of Paragonimus westermani.

42 Life cycle of Paragonimus westermani. Crab or crayfish

43 Life cycle Definitive host: human being Reservoir host: carnivorous animals Habitation: lung & ectopic site Intermediate host: I: Melania snails II: stream crabs, crayfish

44 Infective stage: metacercaria Infective mode: oral route, may via paratenic host (swine) Migration & Preadult wondering Ectopic parasitism: cerebral, abdominal,etc. Eggs discharged with sputum & feces 3 generation of asexual multiplication


46 Pathogenesis Stage take responsibility: adult & preadult Pathological processes –Abscess stage( 脓肿期 ) –Cystic stage( 囊肿期 ) –Scar formation stage( 纤维疤痕期 )

47 4 clinical types –Thoracic (pulmonary type):chest pain, coughing, blood-tinged sputum(hemoptysis) –Abdominal (hepatic type):hepatomegaly –Cranial type: dizzy, headache, epilepsy –Musculocutaneous type: migratable subskin nodule

48 Laboratory diagnosis Disease history + physical examination Etiological diagnosis eggs in sputum or feces by sedimentation Immunological diagnosis for ectopic infections

49 Epidemiology Global main continent except Europe China 23 provinces

50 Paragonimus westermani infection occurs in Asia (especially in China (Taiwan), Corea, India, Japan, Laos, Philippines, Sri Lanka, Thailand, Viet-Nam), Central-West Africa, South America (Ecuador, Peru Venezuela).

51 Principle of control Treat patient: praziquantel Hygienic education Social construction, economic refinement

52 The Ginger Fluke 姜片虫 Fasciolopsis buski 布氏姜片吸虫 Intestinal fluke 肠道吸虫

53 Morphology Adult worm –Like a ginger piece –Big muscular trematode –Have strong suckers , ventral >> oral

54 Adult fluke of Fasciolopsis buski The adult flukes range in size: 20 to 75 mm by 8 to 20 mm

55 Fasciolopsis buskii adult worm

56 Egg –Biggest –Ovoid –Minute operculum –Yellowish –Germ cell inclusions

57 F.buski eggs are released in feces unembryonated. The operculated eggs are oval, brown and measure by um

58 Life cycle of Fascilopsis buski


60 Life Cycle Definitive host: human being Reservoir host: swine, etc. Intermediate host: Planorbis snails Aquatic plant vectors: caltrops, water chestnut, etc. Habitation: small intestine

61 Infective stage: metacercaria Infective route: oral Developmental stages: as Paragonimus 3 generation of asexual proliferation

62 Pathogenesis Factors Traumatic (suckers) Obstructive (due large size) Toxic (excretion, secretion, metabolite)

63 Clinical Manifestation Abdominal pain Acute intestinal obstruction Anemia Generalized edema

64 Laboratory Diagnosis Examination of egg in feces by sedimentation method

65 Epidemiology Aquatic plant raising districts

66 Fasciolopsis buski: is endemic in China (Taiwan), South-East Asia, Malaysia and India.

67 Principle of Control Drug for treatment: praziquantel Water & nightsoil control; Scientific swine raising Hygienic education

68 Introduction 6 species of human schistosomes –Schistosoma japonicum –S. mansoni –S. haematobium –S. intercalatum –S. mekongi –S. malayi

69 Schistosoma japonicum 日本血吸虫

70 Distribution and Epidemic Situation Worldwide –200 million of population infected in 74 countries (S.m. 55;S.h. 55;S.j. 4; S.i. 10; 2; 1) China –11 million in 12 provinces  0.7 million in 8 provinces 50 years

71 Before control After control (1996) Regional distribution of S. japonicum infection in China

72 Morphology Difference from other trematodes –Dioecious adults –Non-opeculate egg –Bifurcated (forked) cercaria invades the final host by skin –Adults parasitize blood vessels

73 Adult –Male (15 mm length) < female (22 mm) –Oral sucker < ventral sucker –2 paralleled guts form a blind caecum in the posterior ends –7 testes in male and single ovary with a tubule uterus in female –Gynecophoric canal (male) in which female repose




77 Egg –Ovoid and non-opeculate –74~106  m × 55~80  m –Contains one miracidium –Bear a minute lateral knob. Miracidium Cercaria

78 S. japonicum S. Mansoni S. haematobium Schistosome egg

79 Schistosome miracidium

80 Schistosome cercaria

81 Life Cycle Eggs discharged  fresh water (hatch)  miracidia  penetrate oncomelania(I.H.)  mother sporocysts (multiplication)  daughter sporocysts (multiplication)  cercariae (infective form)  skin penetration of D.H.  schistosomulum  right heart  lungs  left heart  systemic circulation  portal system  pairing and sexual maturation  mesenteric veins  lay eggs  eggs develop and live in tissue for 21 days( 23% in liver tissue, 60% in intestinal tissue, 17% discharged)


83 Cercarial dermatisis due to avian schistosome

84 Main Points of Life Cycle Residing site: mesenteric vein I.H.(Only one): Oncomelania hupensis No metacercaria and redia stage Two generation of sporocyst Infective stage: cercaria Route of infection: skin penetration

85 Adult of Schistosome in mesenteric veins of hamster

86 Onchomelania hupensis

87 Skin penetration of cercaria  first appearance of eggs: 30~35 days Life spans in human: 4~5 years, longest: 35 years

88 Tissue egg –The egg which can develop and live in tissue Significance of tissue egg –Major pathogenic stage, inflammation and granuloma around the egg –Diagnosis and evaluation of therapeutic efficacy

89 Immunity Concomitant immunity –Host carrying an initial infection of adult schistosomes shows the protection to a cercarial challenge infection ( 攻击性感染) and this protective immunity will disappear with eradication of schistosomes in the host

90 Immuno-evasion: It’s an ability by which the schistosome adult can evade the host immune response. The possible mechanism of evasion. –Acquire host antigen on it surface –Host-like antigen produced by parasite –Changing of tegument very quickly –Parasite may inactivate or down-regulate immune effectors

91 Pathogenesis Schistosomiasis at each stage of the life cycle in human body Cercaria (skin-penetration) –Dermatitis Schistosomula (migration) –Larva migrans Adult: (immunocomplex) –Immuno-nephropathy

92 Tissue egg: principal pathogenic stage Miracidium within egg  SEA  Sensitization of T Cell Th1  IL-2, INF- , TNF  activate macrophage, induce  cell-mediated immunity Th2  IL-4, IL-5  stimulate IgE production or eosinophilia  inflammation and granuloma  fibrosis  portal hypertension  intestinal polyp

93 Clinical Form Acute schistosomiasis –Fever, diarrhea, abdominal pain, enlargement of liver or spleen Chronic schistosomiasis –asymptomatic or diarrhea, abdominal pain, enlargement of liver or spleen Advanced schistosomiasis –Ascites; splenomegaly;collateral circulation; dwarfism; –Ectopic lesion: encephalitis; focal epilepsy

94 Advanced schistosomiasis patient with portal hypertension and ascites

95 A patient with S. j has marked ascites, splenomegaly, umbilical hernia and distended superficial abdominal veins.

96 Diagnosis Parasitological diagnosis (etiological, definitive diagnosis) –Demonstrating eggs by stool examination –Stool examination after concentration (sedimentation) –*Miracidium-hatching from eggs –Rectal biopsy — eggs-demonstration

97 Miracidium-hatching from eggs Necessity: tissue ova; low egg burden due to mass treatment Possibility: Hatch quickly (T:25; limpid water; free of Cl 2 ;light; pH= ) Three tropism:limpidity, phototrophic, ascendancy Swimming in a zigzag way

98 Immunodiagnosis (indirect diagnosis) –Detection of antibodies in serum, urine, saliva by ELISA, but is impossible to distinguish current infection from past infection. –Detection of antigens (circulation anodic and cathodic antigen)

99 Combined diagnosis: including epidemiological antecedent, symptoms and signs, parasitological and immunological examination.

100 Treatment Praziquantel 60 mg/kg divided in 3 doses.

101 Factors of Transmission and Prevention Factors –Source of infection: patients and reservoir host –Intermediate host: Oncomelania –Contact with cercaria-infected water

102 Preventive measures –Detection and treatment of patients and reservoir host –Elimination or control of oncomelania –Protection of susceptible population and avoidance of contact with cercaria-infected water –Prevention of water contamination by human night soil

103 Distinguishing of 3 major schistosomes (see page 54, Table 3-1)


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