introduction to tromatodes phylum platyhelminthes class trematoda order digenea

Introduction to tromatodesIntroduction to tromatodes

Phylum PlatyhelminthesClass TrematodaOrder Digenea

MorphologyMorphology

• Adult worm– Flattened (flatworm) and leaf like– Sucker: oral & ventral (fluke)– Body wall: musculo-tegumental sac– Parenchyma (structure between body wall and i

nternal organs): connective tissue fibers, cells and space between them

– Digestive tract: not intact

i.e. no anal opening, caecum– Reproductive system: hermaphrodite (monoeci

ous) exception of schistosome– Muscular system– Nervous system– Excretory system

• Egg

– Size divergent

– Ovoid

– Operculum (exception of that of schistosome)

– Content: ovum , vitelline cells, or miracidium

Egg of Clonorchis sinensis

Egg of Paragonimus westermani

Egg of Fasciolopsis buski

S. japonicum S. Mansoni S. haematobium

Schistosome egg

Features Reflecting Features Reflecting Adaptation to ParasitismAdaptation to Parasitism

• Organs of attachment highly developed

• Retardation of digestive system

• Highly developed reproductive system

Life CycleLife 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

Important SpeciesImportant Species

• Liver fluke: Clonorchis sinensis

• Intestinal fluke: Fasciolopsis buski

• Lung fluke: Paragonimous westermani

P. skrjabini

• Blood fluke: Schistosoma spp.

The Liver FlukeThe Liver Fluke肝吸虫肝吸虫

Clonorchis sinensisClonorchis sinensis中华支睾吸虫中华支睾吸虫

Introduction Introduction

• Parasite of biliary passage

• Cause “clonorchiasis”

• A common trematode in Far East

• First report

1874 oversea Chinese in India


• Adult worm

– Size & Shape

like the seed of sunflower

– Sucker: oral = ventral

– 2 dendritic testes lie in tandem to each other in t

he posterior region (clonorchis)

Adults of Clonorchis sinensis

Cross section of Clonorchis sinensis adult in the hepatic bile duct

• Egg

– Size: smallest

– Shape: just like sesame

– Color: yellowish brown

– Operculum distinct: shoulder, knob

– Content: miracidium

Clonorchis sinensis egg. These are small operculated eggs. Size 27 to 35 µm by 11 to 20 µm. 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.

Egg of Clonorchis sinensis

Life cycle of Clonorchis sinensis


• 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

– 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

PathogenesisPathogenesis

• Due to adult worm

• Mechanism

– Mechanical: sucker

– Chemical: excretions, secretions, metabolite

– Biological: nutrition deprivation

• Pathological process

– Inflammation Proliferation

ThickeningOcclusion

– Extensive involvementFibrosis of the liver

Clinical ManifestationsClinical Manifestations

• Acute stage: allergic reaction

• Chronic stage: functional impairment of liver (Cholangitis, Cholecystitis, Bile stone, Jaundice, etc)

• Advanced stage: portal cirrhosis & malignancy

Laboratory DiagnosisLaboratory Diagnosis

• Etiological

– Examination of egg in feces by sedimentation

method

– Duodenal aspiration

• Immunological

– ELISA to detect antiboby or antigen

EpidemiologyEpidemiology

• Distribution

– Far East

(China, South Korea, Japan, etc.)

– 24 provinces in China

(Guangdon: 5 million infected etc.)

Endemic FactorsEndemic Factors

• Source of infection: mainly wild carnivores

• I,II intermediate host in the same water-

field

• Mode of fish breeding

• Dinning habit & Customs

Principle of ControlPrinciple of Control

• Cure patients & carrier

• praziquantel:25mg/kg, tid, 2 days

• Control reservoir host

• Carry out scientific fish-breeding

• Hygienic educationnot eating raw or undercooked fishes

Paragonimus westermaniParagonimus westermani卫氏并殖吸虫卫氏并殖吸虫

Paragonimus skrjabiniParagonimus skrjabini(Paragonimus szechuanensis)(Paragonimus szechuanensis)

斯氏狸殖吸虫斯氏狸殖吸虫

The Lung FlukeThe Lung Fluke

• Genus paragonimus

• Zoonotic parasite (cause zoonosis)

• Animal infection> human infection

• 2 major species in China

IntroductionIntroduction

• Pathogen of lung disease

• Endemic hemoptysis

• Favorite lodging site: lung

• Ectopic site: brain, abdomen, muscle, etc.


• Adult worm

• Body thick (a half piece of a bean grain)

• Tegument: spinous

• Sucker: oral = ventral

• Parallel arrangement of reproductive organlobular testes (posterior)lobular ovary & uterus (anterior)

Cross section of lung containing adult Paragonimus westermani.

• Egg

– Median size, ovoid (water pot)

– Golden yellow

– Distinctive & wide operculum

– Contain 1 germ cell & several yolk cells

Egg of Paragonimus westermani.

Life cycle of Paragonimus westermani.

Crab or crayfish

Life cycleLife cycle

• Definitive host: human being

• Reservoir host: carnivorous animals

• Habitation: lung & ectopic site

• Intermediate host:I: Melania snailsII: stream crabs, crayfish

• 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


• 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 )

• 4 clinical types– Thoracic (pulmonary type):chest pain, coughin

g, blood-tinged sputum(hemoptysis)– Abdominal (hepatic type):hepatomegaly– Cranial type: dizzy, headache, epilepsy– Musculocutaneous type: migratable subskin no

dule

Laboratory diagnosisLaboratory diagnosis

• Disease history + physical examination

• Etiological diagnosiseggs in sputum or feces by sedimentation

• Immunological diagnosisfor ectopic infections


• Globalmain continent except Europe

• China 23 provinces

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).

Principle of controlPrinciple of control

• Treat patient: praziquantel

• Hygienic education

• Social construction, economic refinement

The Ginger FlukeThe Ginger Fluke姜片虫姜片虫

Fasciolopsis buskiFasciolopsis buski布氏姜片吸虫布氏姜片吸虫

Intestinal flukeIntestinal fluke肠道吸虫肠道吸虫


• Adult worm

– Like a ginger piece

– Big muscular trematode

– Have strong suckers ， ventral >> oral

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

Fasciolopsis buskii adult worm

• Egg

– Biggest

– Ovoid

– Minute operculum

– Yellowish

– Germ cell inclusions

F.buski eggs are released in feces unembryonated. The operculated eggs are oval, brown and measure 130-150 by 78-100 um

Life cycle of Fascilopsis buski


• Definitive host: human being

• Reservoir host: swine, etc.

• Intermediate host: Planorbis snails

• Aquatic plant vectors: caltrops, water chestnut, etc.

• Habitation: small intestine

• Infective stage: metacercaria

• Infective route: oral

• Developmental stages: as Paragonimus

• 3 generation of asexual proliferation

Pathogenesis FactorsPathogenesis Factors

• Traumatic (suckers)

• Obstructive (due large size)

• Toxic (excretion, secretion, metabolite)

Clinical ManifestationClinical Manifestation

• Abdominal pain

• Acute intestinal obstruction

• Anemia

• Generalized edema

Laboratory DiagnosisLaboratory Diagnosis

• Examination of egg in feces by sedimentation method


• Aquatic plant raising districts

Fasciolopsis buski: is endemic in China (Taiwan), South-East Asia,

Malaysia and India.

Principle of ControlPrinciple of Control

• Drug for treatment: praziquantel

• Water & nightsoil control; Scientific swine raising

• Hygienic education

IntroductionIntroduction

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

Schistosoma japonicumSchistosoma japonicum

日本血吸虫

Distribution and Epidemic SituationDistribution and Epidemic Situation

• Worldwide– 200 million of population infected in 74

countries(S.m. 55; S.h. 55; S.j. 4; S.i. 10; S.me. 2; S.ma. 1)

• China– 11 million in 12 provinces 0.7 million in 8

provinces

50 years

Before control After control (1996)

Regional distribution of S. japonicum infection in China

Morphology Morphology

• Difference from other trematodes

– Dioecious adults

– Non-opeculate egg

– Bifurcated (forked) cercaria invades the final ho

st by skin

– Adults parasitize blood vessels

• Adult

– Male (15 mm length) < female (22 mm)

– Oral sucker < ventral sucker

– 2 paralleled guts form a blind caecum in the pos

terior ends

– 7 testes in male and single ovary with a tubule

uterus in female

– Gynecophoric canal (male) in which female rep

ose

• Egg

– Ovoid and non-opeculate

– 74~106 m × 55~80 m

– Contains one miracidium

– Bear a minute lateral knob.

• Miracidium

• Cercaria

S. japonicum S. Mansoni S. haematobium

Schistosome egg

Schistosome miracidium

Schistosome cercaria

Life CycleLife CycleEggs discharged fresh water (hatch) miracidia pe

netrate oncomelania(I.H.)mother sporocysts (multiplica

tion) daughter sporocysts (multiplication) cercariae

(infective form) skin penetration of D.H. schistosomul

um right heart lungs left heart

systemic circulation portal system pairing and sexu

al maturation mesenteric veins lay eggs eggs develo

p and live in tissue for 21 days( 23% in liver tissue, 60% in int

estinal tissue, 17% discharged)

Cercarial dermatisis due to avian schistosome

Main Points of Life CycleMain 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

Adult of Schistosome in mesenteric veins of hamster

Onchomelania hupensis

Skin penetration of cercaria first

appearance of eggs: 30~35 days

Life spans in human: 4~5 years, longest: 35

years

• 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

ImmunityImmunity

• Concomitant immunity

– Host carrying an initial infection of adult schist

osomes shows the protection to a cercarial chall

enge infection ( 攻击性感染） and this protecti

ve immunity will disappear with eradication of

schistosomes in the host

• 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


Schistosomiasis at each stage of the life cycle in human body

• Cercaria (skin-penetration)– Dermatitis

• Schistosomula (migration)– Larva migrans

• Adult: (immunocomplex)– Immuno-nephropathy

• Tissue egg: principal pathogenic stage

Miracidium within eggSEASensitization of T Cell

Th1IL-2, INF-, TNF activate macrophage, induce cell-mediated immunity

Th2IL-4, IL-5 stimulate IgE production or eosinophilia

inflammation and granuloma fibrosis portal hypertension

intestinal polyp

Clinical FormClinical Form

• Acute schistosomiasis– Fever, diarrhea, abdominal pain, enlargement of liver o

r 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

Advanced schistosomiasis patient with portal hypertension and ascites

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

DiagnosisDiagnosis

• Parasitological diagnosis (etiological, definitive diagnosis)– Demonstrating eggs by stool examination– Stool examination after concentration

(sedimentation)– *Miracidium-hatching from eggs– Rectal biopsy — eggs-demonstration

Miracidium-hatching from eggsMiracidium-hatching from eggs

Necessity: tissue ova;

low egg burden due to mass treatment

Possibility:• Hatch quickly (T:25; limpid water; free of

Cl2;light; pH=6.8-7.8)

• Three tropism:limpidity, phototrophic, ascendancy• Swimming in a zigzag way

• Immunodiagnosis (indirect diagnosis)

– Detection of antibodies in serum, urine, saliva b

y ELISA, but is impossible to distinguish curre

nt infection from past infection.

– Detection of antigens (circulation anodic and ca

thodic antigen)

• Combined diagnosis: including

epidemiological antecedent, symptoms and

signs, parasitological and immunological

examination.

TreatmentTreatment

Praziquantel 60 mg/kg divided in 3 doses.

Factors of Transmission and Factors of Transmission and PreventionPrevention

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

• Preventive measures– Detection and treatment of patients and reservoir h

ost

– 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

Distinguishing of 3 major Distinguishing of 3 major schistosomesschistosomes

(see page 54, Table 3-1)

introduction to tromatodes phylum platyhelminthes class trematoda order digenea

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