Trematodes

M E D I C A L

P A R A S I T O L O G Y

Table 1: Comparison of Liver Fluke and Intestinal Fluke Aspects

Fasciola hepatica

Fasciolopsis buski 

Disease

Fascioliasis

Fasciolopsiasis Fasciolopsiasis

Geographic

Cosmopolitan distribution

Asia and Indian subcontinent

Habitat

Intrahepatic Intrahepatic bile duct

Small intestine intestine (Duodenum)

Reservoir host

Sheep and cattle

Farmed Pigs

Intermediate

1st - Lymnaea snails

1st - Segmentina / Hippeutis snails

hosts

2nd - Aquatic vegetation

2nd - Aquatic vegetation

Transmission Transmiss ion

Ingestion of raw, fresh water 

Ingestion of raw, fresh water 

vegetation (watercress)

vegetation (water caltrop / bamboo)

Metacercariae Metacercariae

Metacercariae Metacercariae

Infective stage   Appearance

Leaf-shaped, Leaf-s haped, 20 - 30 mm length and brown to pale gray in colour 

  Anterior end Sucker (organ)

Fleshy, dark red, elongate elongate -ovoid, -ovoid, 20 - 75 mm length

A distinct conical conical projection projection

No cephalic cephalic cone seen

Oral and ventral suckers to attach

Oral and ventral suckers to attach

to biliary duct lining

to small intestinal lining

Monoecious with highly branched

Monoecious with branched ovary

testes and ovaries

and posterior dendritic testes

Intestine

Extensively branched branched caeca

Unbranched Unbranched intestinal intestinal caeca

Released ovum

Large, ellipse to oval, more flat

Large, ellipsoidal, more rounded

(Unembryonated)

operculum at pole and granular 

operculum at pole and granular 

yellowish brown

yellowish brown

Embryonated

Miracidium Miracidium is fully formed and

Miracidium is fully formed and

egg / ovum

ready to emerge

ready to emerge

Pathogenicity Pathogenicity

50% asymptomatic asymptomatic

Mostly light and asymptomatic asymptomatic

Sex organs

  Acute phase

Chronic phase

Lab diagnosis diagnosis

Treatment Treatment

T R E M A T O D E S

Fever, tender hepatomegaly,

Diarrhea, abdominal pain, fever,

abdominal pain, vomiting,

ascites, and intestinal obstruction

anemia, urticaria, due to damages

due to attachment of worm in the

to liver parenchyma by larvae

intestinal mucosa lining

Biliary obstruction, inflammation,

Inflammation, chronic ulceration,

biliary cholic, jaundice, pipe stem

hemorrhage, and abscesses of the

liver and portal cirrhosis, halzoun

small intestine intestine

Samples: Stool, Aspirates

Samples: Stool, Vomitus

O&P exam, Eosinophilia, CT scan

O&P exam, Eosinophilia, Imaging

Triclabendazole Triclabendazole,, Bithionol Bithionol

Praziquantel, Praziquantel, Niclosamide Niclosamide

A N D

C E S T O D E S



A N A N D

2 0 1 1

1

M E D I C A L

P A R A S I T O L O G Y

Table 2: Comparison of Lung Fluke and Blood Fluke Aspects

P aragonimus

Disease

Paragonimiasis

Schistosomiasis

Geographic

Asia and Indian subcontinent

Depend on species

Habitat

Lungs (commonly right)

Mesenteric blood vessels

Reservoir host

Tiger, Predatory animals

None specified

Intermediate

1st ± Semisulcospira snails

Bulinus / Biomphalaria /

hosts

2nd ± Crustacean (crab / crayfish)

Oncomelania snails

Transmission

Ingestion of raw / poorly cooked

Penetration of human skin during

crab or crayfish

swimming exposure

Metacercariae

Fork-tailed cercariae

Infective stage   Appearance

westermani

Schistosoma spp.

Plump, oval, reddish brown,

Bilaterally symmetry, tegument

spined, 7 - 12 mm in length   Anterior end Sucker (organ)

covered, 10 - 20 mm in length

Slightly broader than posterior

Sharp ended

Oral and ventral suckers to attach

Oral and ventral suckers armed

to lung parenchyma

with delicate spines

Monoecious with lobed testes

Diecious, sexual reproduction via

below the ovaries

gynaecophoric canal

Intestine

Blind bifurcated gut

Blind gut with bifurcated caeca

Released ovum

Oval, yellowish-brown, with thick

Non-operculated eggs with thin

(Unembryonated)

smooth shell and a flattened

smooth shell, fully embryonated

operculum

when laid

Embryonated

Miracidium is fully formed and

Miracidium is fully formed and

egg / ovum

ready to emerge

ready to emerge

Pathogenicity

Pulmonary, extrapulmonary

Often chronic infection

  Acute phase

Brown fibrous tissue cysts,

Sex organs

Chronic phase

Katayama fever, high fever,

bronchopneumonia, bronchitis,

hepatosplenomegaly, eosinophilia,

chest pain, dyspnoea, recurrent

dysentery, lymphadenopathy due to

hemoptysis, cough

oviposition of female worms

Blood-tinged mucoid gelatinous

Granulomatous reactions and

sputum containing eggs and

fibrosis in the affected organs

Charcot-Leyden crystals Lab diagnosis

Treatment

T R E M A T O D E S

Samples: Stool, Sputum

Samples: Stool, Urine

O&P exam, Eosinophilia, CT scan

O&P exam, Serologic, Biopsy

Praziquantel, Bithionol

Praziquantel, Antimony

A N D

C E S T O D E S



A N A N D

2 0 1 1

2

M E D I C A L

Char t : Pathogeni it of i er  l Biliary Inf 

  

A R A S I T O L O G Y

e

ion

Young flukes released in duodenum after  the ex cystation luke migrate to per itoneal cavity and live r parenchyma via duodenal wall

ecrotic lesions in liver  parenchyma infiltrated witheosinophils eosinophilia) ever , tender hepatomegaly, abdominal pain, ur ticar ia, anemia and jaundice

ature adult worm settle in bile duct and cause biliary cholic and epigastr ic pain  Adult worm an d metabolic waste cause biliary obstruction and inflammation

ibrosis f orms pipe st em live r  white appearance of bile ducts after  fibrosis) inal outcome will be portal cirrhosis that may lead to death Halzoun

Ingestion of raw inf ected liver  E

Young worm attach to pharyngeal mucosa

Pain, edema & blood inter f eres breathing

et lodged in ectopic f oci abscess)

Per itoneal cavity, lungs, brain ventr icles

opic Inf  ction igration of adult worm

able 4: A

lt

orpholog y of 

ng

orm

l

e Egg /

a

Pl mp, egg haped, oval

-

eddi h brown

off ee bean)

S b-terminal oral

er 

arger ventral

er  at middle

S r f ace covered by mall pines nbranched bif  rcated gut

-

Poster ior  parallel lobed testes

-

obed ovary above the testes

-

aterally located vitellar ia

T R E M A T O D E S

A N D

C E S T O D E S



A N A N D

2 0 1 1

3

M E D I C A L

Pulmo

P A R A S I T O L O G Y

ary parago imiasis

 Acute infection (Less than 20 worms in right lung) 1. No clinical symptoms during incubation period of about 20 days 2. Early stage  diarrhea, dyspnoea, urticaria, chest pain, cough, abdominal pain 3. Fluke penetrate lungs  hemorrhage and inflammation  necrosis of lung parenchyma . Formation of brown coloured, fibrous tissue capsule or cyst of 1 to 2 cm in di ameter  5. 1 or 2 worms in cyst  deposit eggs  swelling and rupture of cyst into bronchioles 6. Lung lesions + allergic reactions  bronchopneumonia, bronchitis, bronchiectasis and pleural thickening due to presence of worms 7. Ectopic lesions  intestine, periton eal cavity, liver, lymph nodes, heart, muscles, brain

Chronic infection (Mild with cough and respiratory discomfort) 1. Produce mucoid-gelatinous, blood -tinged sputum + eggs and Charcot -Leyden crystals 2. Reddish brown sputum due to recurrent haemoptysis (hemor rhage and erythrocytes) 3. Severe chronic cough and stabbing pains in the chest due to lung infection . Complications  empyema, pleural effusion and pneumothorax

Extrap ulmo ary parago imiasis 1. Cerebral infection in young people  granuloma and abscess in brain 2. Signs  N/V, headache, fever, vision disturbances, increased CSF pressure 3. Recurrent cerebral / spinal  epileptic seizures and paralysis . Abdominal infection  granuloma or abscess in liver, spleen, abdominal cavity 5. Cutaneous infection  adult worms or egg s in subcutaneous tissues 6. Normally gives a better prognosis than the pulmonary paragonimiasis

Table 5: Comparison of Blood Fluke Species

S. mansoni

S. japonicum

  Africa , East Mediterranean

Eastern Asia, China

S. haematobium Africa, East Mediterranean

Biomphalaria spp. snails

Oncomelania spp. snails

Bulinus spp. snails

Elongated eggs have

Subspherical eggs have

Elongated eggs have a

prominent lateral spines

lateral knob (vestigial spine)

characteristic terminal spine

Eggs discharged in the feces

Eggs discharged in the feces

Eggs discharged in the urine

T R E M A T O D E S

A N D

C E S T O D E S



A N A N D

2 0 1 1

4

M E D I C A L

Lif e

Cycl e of Schistosome s

-

Parasite egg released

P A R A S I T O L O G Y

rupture relea sing mature miracidium in f resh water 

-

iracidium penetrate f resh water  snail¶s f oot

-

erm cells divide to f orm secondary sporocyst

-

erm cells re-divide to f orm thousands of inf ective cercar iae

-

ighly motile cercar iae attach and penetrate human skin when comes into contact

-

transf orm into pr imary sporocyst migrate to snail¶s hepatopancreas

Cercar iae secrete enzymes to break down skin protein

-

allow penetration of head

he tail is shed to f orm schistosomula that remains in skin f or 

-

emerge f rom snail

to

days

Schistosomula migrates to lung f or  f ur the r development via post capillary venule

-

he parasite migrate to live r sinusoids and develop oral sucker 

f eed on

BC

-

igration to mesenter ic, rectal or  per ive sical venous plexus and produce eggs

-

ature eggs crosses the digestive tract through release of proteolytic enzymes

able : Pathogenicity of Schistosoma spp. Pathology of S. -

¡

¢

£

¤

¥

£

i, S. j   

 

¢  

¦  

¥

£  

i  §

¨

Pathology of S.

¡   

Katayama f e ver 

-

ep atic per isinusoidal egg granulomas

©

¢



¡

¢

t  i   

¥

-

Scarr ing

Symmer ¶s pipe stem per ipor tal fibrosis

-

Calcification

-

Por tal hyper ten sion

-

S uamous cell carcinoma

A N D

C E S T O D E S



A N A N D

  

¨

¡   

ematur ia

-

T R E M A T O D E S

 

2 0 1 1

5

M E D I C A L

P A R A S I T O L O G Y

Table 7: Fundamentals of Cestodes Term

Explanation

Scolex

Knob-like head equipped with hooks as organ of attachment

Proglottids

Series of flat, rectangular body segments that grows from neck

Strobilus

Chain of proglottids reaching a length of .6 to 6.1 meter 

Tegument

Absorptive outer covering that allow exchange of materials

Hermaphroditic

Male & female reproductive organs present in mature proglottids

Table 8: Comparison of Tapeworms Aspects

T aenia

Disease

Taeniasis

Cysticercosis

Geographic

More prevalent

Less prevalent

Habitat

Upper jejenum

Upper jejenum

Intermediate host

Cow (Beef meat)

Pig (Pork meat)

Length

saginata

T aenia

to 8 meter

2 to

solium

meter 

Transmission

Ingestion of raw beef

Ingestion of raw pork

Infective stage

Cysticercus bovis

Cysticercus cellulosae

Scolex

Large quadrate without rostellum

Small, globular with rostellum

and hooks

armed with hooklets

Long

Short

Neck Suckers

without hooks

with small hooks

Ovaries

2 without any accessory lobe

2 with an accessory lobe

Testes

300 to 00 follicles

150 to 200 follicles

Gravid

20 mm x 5 mm, trunk with 15 - 20

12 mm x

Proglottids

main lateral branches each side,

main lateral branches each side,

may be single detached

may be in short chains of 2 to 3

Brown, spherical with hexacanth

Brown, spherical with hexacanth

embryo + 3 pairs of hooklets,

embryo + 3 pairs of hooklets,

surrounded by thick yellow-brown

surrounded by thick yellow-brown

embryophore, not float in saline

embryophore, not float in saline

Praziquantel

Praziquantel

Eggs

Treatment

mm, trunk with 7 - 13

Eggs in feces  Pig / Cow ingest eggs or gravid proglottids  Oncosphere hatches  Penetrate intestinal wall  Enter portal vessels / mesenteric lymphatics  Circula tion  Reach striated muscle  Develop into cysticercus bovis  Ingested by man  larvae hatch in small intestine  Anchor to mucosa  Mature into adult  Produce gravid proglottids

T R E M A T O D E S

A N D

C E S T O D E S



A N A N D

2 0 1 1

6

M E D I C A L

P A R A S I T O L O G Y

Cysticercosis

1. Human acts as an intermed iate host by ingesting the eggs 2. The larvae able to invade the tissues and enter bloodstream 3. Spread to many organs such as skeletal muscle, heart, eye, brain . Forms a cyst called cysticerci in the organ migrated 5. Diarrhea, constipation, flatulence and weight loss 6. Proglottids become lodged in t he appendix and cause appendicitis

Neurocysticercosis 1. Cysticercus larvae migrate to brain 2. Neurological symptoms: headache and seizures

Autoinf ection by vomiting 1. Eggs laid by infesting tapeworm are pushed back into stomach 2. When eggs pass through intestine , the larvae hatches and infect

Seven (7) larval stages: Cysticercosis, Cysticercoid, Procercoid, Plerocercoid, Coenurus, Coracidium, Hydatid cyst

T R E M A T O D E S

A N D

C E S T O D E S



A N A N D

2 0 1 1

7