Transcript MEDICAL PARASITOLOGY

Introduction to tromatodes
Phylum Platyhelminthes
Class Trematoda
Order Digenea
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
– Digestive tract: not intact
i.e. no anal opening, caecum
– Reproductive system: hermaphrodite
(monoecious) 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
Adaptation to Parasitism
• Organs of attachment highly developed
• Retardation of digestive system
• Highly developed reproductive system
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
Important Species
• Liver fluke: Clonorchis sinensis
• Intestinal fluke: Fasciolopsis buski
• Lung fluke: Paragonimous westermani
P. skrjabini
• Blood fluke: Schistosoma spp.
The Liver Fluke
肝吸虫
Clonorchis sinensis
中华支睾吸虫
Introduction
• Parasite of biliary passage
• Cause “clonorchiasis”
• A common trematode in Far East
• First report
1874 oversea Chinese in India
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)
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
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
– 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
Pathogenesis
• Due to adult worm
• Mechanism
– Mechanical: sucker
– Chemical: excretions, secretions, metabolite
– Biological: nutrition deprivation
• Pathological process
– Inflammation Proliferation
ThickeningOcclusion
– Extensive involvementFibrosis of the liver
Clinical Manifestations
• Acute stage: allergic reaction
• Chronic stage: functional impairment of
liver (Cholangitis, Cholecystitis, Bile stone,
Jaundice, etc)
• Advanced stage: portal cirrhosis &
malignancy
Laboratory Diagnosis
• Etiological
– Examination of egg in feces by sedimentation
method
– Duodenal aspiration
• Immunological
– ELISA to detect antiboby or antigen
Epidemiology
• Distribution
– Far East
(China, South Korea, Japan, etc.)
– 24 provinces in China
(Guangdon: 5 million infected etc.)
Endemic Factors
• Source of infection: mainly wild carnivores
• I,II intermediate host in the same waterfield
• Mode of fish breeding
• Dinning habit & Customs
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
Paragonimus westermani
卫氏并殖吸虫
Paragonimus skrjabini
(Paragonimus szechuanensis)
斯氏狸殖吸虫
The Lung Fluke
•
•
•
•
Genus paragonimus
Zoonotic parasite (cause zoonosis)
Animal infection> human infection
2 major species in China
Introduction
• Pathogen of lung disease
• Endemic hemoptysis
• Favorite lodging site: lung
• Ectopic site: brain, abdomen, muscle, etc.
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)
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.
Crab or
crayfish
Life cycle of Paragonimus westermani.
Life cycle
•
•
•
•
Definitive host: human being
Reservoir host: carnivorous animals
Habitation: lung & ectopic site
Intermediate host:
I: Melania snails
II: 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
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)
• 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
Laboratory diagnosis
• Disease history + physical examination
• Etiological diagnosis
eggs in sputum or feces by sedimentation
• Immunological diagnosis
for ectopic infections
Epidemiology
• Global
main 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 control
• Treat patient: praziquantel
• Hygienic education
• Social construction, economic refinement
The Ginger Fluke
姜片虫
Fasciolopsis buski
布氏姜片吸虫
Intestinal fluke
肠道吸虫
Morphology
• 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
Life Cycle
•
•
•
•
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 Factors
• Traumatic (suckers)
• Obstructive (due large size)
• Toxic (excretion, secretion, metabolite)
Clinical Manifestation
• Abdominal pain
• Acute intestinal obstruction
• Anemia
• Generalized edema
Laboratory Diagnosis
• Examination of egg in feces by
sedimentation method
Epidemiology
• Aquatic plant raising districts
Fasciolopsis buski: is endemic in China
(Taiwan), South-East Asia,
Malaysia and India.
Principle of Control
• Drug for treatment: praziquantel
• Water & nightsoil control; Scientific swine
raising
• Hygienic education
Introduction
• 6 species of human schistosomes
–
–
–
–
–
–
Schistosoma japonicum
S. mansoni
S. haematobium
S. intercalatum
S. mekongi
S. malayi
Schistosoma japonicum
日本血吸虫
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;
S.me. 2;
S.ma. 1)
• China
50 years
– 11 million in 12 provinces  0.7 million in 8
provinces
Before control
After control (1996)
Regional distribution of S. japonicum infection in China
Morphology
• Difference from other trematodes
– Dioecious adults
– Non-opeculate egg
– Bifurcated (forked) cercaria invades the final
host 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
posterior ends
– 7 testes in male and single ovary with a tubule
uterus in female
– Gynecophoric canal (male) in which female
repose
• 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 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)
Cercarial dermatisis due to avian schistosome
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
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
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
• 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
Pathogenesis
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 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
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
Advanced schistosomiasis patient
with portal hypertension and ascites
A patient with S. j has marked ascites, splenomegaly,
umbilical hernia and distended superficial abdominal veins.
Diagnosis
• 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 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
by ELISA, but is impossible to distinguish
current infection from past infection.
– Detection of antigens (circulation anodic and
cathodic antigen)
• Combined diagnosis: including
epidemiological antecedent, symptoms and
signs, parasitological and immunological
examination.
Treatment
Praziquantel 60 mg/kg divided in 3 doses.
Factors of Transmission and
Prevention
• 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
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
Distinguishing of 3 major
schistosomes
(see page 54, Table 3-1)