Trematodes by Dr. Rakesh Prasad Sah

1. Dr. Rakesh Prasad Sah
Assistant Professor, Microbiology

2. • Multicellular eukaryotic helminths
• Unsegmented leaf-like organisms
• Also called as “FLUKES”
• Size: 1mm to several centimeters
• MONECIOUS except for schistosomes
(DIECIOUS)

3. trematodes or flukes - when they say
‘flat’ worms they mean it
• Small doro-ventrally flattened worms,
• No body cavity,
• Incomplete digestive tract
• .
• No circulatory or respiratory organs
• simple ladder nervous system.

4. • Two suckers oral & ventral
– Oral sucker (nourishment)
– Ventral sucker or acetabulum (to
attach to the host)
• Most of trematodes are
hermaphrodite (self fertilization
occurs) except the schistosomes

5. General Rules
• All are hermaphroditic
• All require two intermediate hosts
• Eggs of all trematodes are operculated
• The infective stage is metacercariae
Schistosomes

6. Taxonomical Classification of trematodes
Superfamily Family Genus Species
Schistosomatoedea Schistosomatoedea Schistosoma S. haematobium
S. mansoni
S. japonicum
S. intercalatum
Paramphistomatoidea Paramphistomatoidea Watsonius W. watsoni
Gastrodiscoides Gastrodiscoides G. hominis
Echinostomatoidea Fasciolidae Fasciola F. hepatica
Fasciolopsis F. buski
Opisthorchioidea Opisthorchiidae Clonorchis C. sinensis
Opisthorchis O. felineus
Heterophydiae Hetrophyes H. heterophyes
Metagonimus M. yokogawai
Plagiorchioidea Troglotrematidae Paragonimus P. westermani

7. Classification of trematodes according to their habitat
Habitat Trematode
1 Blood trematodes (Blood flukes)
In the vesical and pelvic venous plexuses S. hematobium
In the inferior mesentric vein S. mansoni
In the superior mesentric vein S. japonicum
2 Hepatic trematodes (Liver flukes) F. hepatica, C. sinensis,
Opisthorchis sp.
3 Intestinal trematodes (Intestinal flukes)
Small intestine F. buski, H. heterophyes, M.
yokogawai, W. watsoni
Larger intestine G. hominis
4 Lung trematodes (Lung flukes) P. westermani

8. Blood Flukes (Shistosomes)
• Causative agent of disease schistosomiaisis.
• Diecious trematodes
• Males are broder than females
• Formerly known as Bilharzia after Theodor
Bilharz who discovered the parasite in the
blood of mesenteric veins of a young man in
Cairo in 1851.

9. MALE& FEMALE SHISTOSOMULAE IN BLOOD
VESSEL

10. Differentiating charcters of S. haematobium, S. mansoni, and S.
japonicum
Character S. haematobium S. mansoni S. japonicum
Geographical distribution
East
Mediterranean
and African
countries, India &
Turkey
Africa, Americas
and the East
Mediterranean
China,
Philippines,
Indonesia and
Thailand
Host Involved
Definitive host Man Man Man and domestic
animals
Intermediate
host
Bulinus sp. Biomphalaria sp. Oncomelania sp.

11. Differentiating charcters of S. haematobium, S. mansoni, and S.
japonicum
Character S. haematobium S. mansoni S. japonicum
Morphology of Worms
Male
Size 10-15mm X 0.8mm 6-12mm X 1mm 12-20 mm X 0.5mm
Integume
nt
Covered with minute
tuerculations
Covered with monre
conspicuous
tuberculations
Covered with minute
spines
Female
Size 20mm X 0.25mm 7-17 mm X 0.25mm 26 mm X 0.3mm
Ovary Present in the posterior
third of the body
Present in the
anteriour half of the
body
Present in the middle
of the body
Uterus Contains 20-200eggs Contains 1-3 eggs Contains 50 or more
eggs

12. Differentiating characters of S. haematobium, S. mansoni, and S. japonicum
Character S. haematobium S. mansoni S. japonicum
Egg
Size 110-170µm X 40-70µm 115-180µm X 40-70µm 70-100µm X 55-
65µm
Shape Elongated Elongated Oval
Shell Thin, smooth shell Thin, smooth shell Smooth,
relatively thick
Anterior end Rounded Pointed and curved Rounded
Posterior end Terminal spine present Lateral spine present Lateral knob
present
Eggs
discharged in
Urine Faeces Faeces

16. Pathogenesis
• Following skin penetration by cercariae  A pruritic
rash and dermatitis may occur.
Intestinal bilharziasis
• S. mansoni
• Intestinal Bilharziais or schistosomal dysentery
• Intestinal symptoms
– Abdominal pain & bloody diarrhoea.

18. Acute schistosomiasis or katyama fever
• occurs with S. japonicum and S. mansoni and rarely with S.
heematobium.
• Symptoms
– High fever
– Hepatosplenomegaly
– Lymphadenopathy
– Dysentery

19. Haematuria
• Painless haematuria
• Initially microscopic, but becomes gross if infection is
heavy.
• Occurs in case of S. haematobium infection.
• Calculi may form in bladder due to deposition of
oxalate and uric acid crystals around eggs.
• Chronic schistosomiasis  urinary bladder cancer.

20. Lab diagnosis
• Microscopy
– Detection of characteristic eggs.
• Cystoscopy and biopsy of lesions
in bladder
• Serology
– IFAT
– ELISA
– CFT
– RIA

21. Fasciola hepatica
(LIVER FLUKE)
• The sheep liver fluke and the common liver fluke
• Parasite of herbivorous animals.
• Lives in biliary passages of liver.
• Occasionally found in man.
• Exist in 6 morphological forms – adult, miracidium, sporocyst,
1st generation redia, 2nd generation redia, cercaria &
metacercaria.
• Leaf like, 30mm x 15mm, grey or brown.
• Anteriorly conical projection, posteriorly round.

22. • 5yr life span in sheep & 10yr in Man.
• Eggs are operculated, bile stained and
measure 140 um x 80 um.
• Eggs immature when passed in faeces, can
develop only in water.
• contains immature larva (miracidium)
• Shell of egg is thin with smooth surface.
• Can not be differentiated from egg of F. buski.

25. Clinical features
• Fascioliasis
• Fever
• abdominal pain
• hepatomegaly
• Ascites and Jaundice
• Eosinophilia – acute disease.
• In untreated patients – intermitent biliary obstruction,
cholecystitis, cholelithiasis & development of strictures.

26. Lab diagnosis
• Stool examination –
operculated eggs
• Eosinophilia
• ELISA

27. Clonorchis sinensis
(Chinese Liver Fluke)
• Parasite of man, dogs and cats in the
southeast of Asia
• Common: China, Korea ,Japan,
Taiwan and Vietnam
• Adult worm located in the biliary tract.

28. • Splindloid flukes

31. Clinical features
• Clonorchiasis
• Epigastric pain
• Indigestion
• Liver necrosis and tenderness
• Liver dysfunctions related to fluke burden
• Diarrhea, hepatomegaly, jaundice and ascites, in heavier
infections

32. • Diagnosis
eggs in the feces or bile
• Eosinophilia
• ELISA
• CFT

33. Fasciola buski
(INTESTINAL FLUKES)
• Also k/a large or Giant Intestinal Fluke
• Largest trematode
• Assam and west bengal in India
• Exist in 6 forms – adult, miracidum,
sporocyst, redia, cercaria, metacercaria.
• Adult live in small intestine of humans and pig.
• Size 20 – 75 mm x 8-20 mm x 0.5 – 3mm.
• 25,000 eggs per day

34. 5 cm

35. • Eggs measure
130 – 150 um x
60 – 90 um
• Bile stained.

38. Clinical features
• Fasciolopsis
• Damage  traumatic, mechanical & toxic effects
• Ulceration at the site of attachment
• Worm  partial obstruction of bowel
• Diarrhoea, anorexia, nausea, vomiting, abodominal pain,
fever, & mild anaemia.

39. Lab diagnosis
• Stool examination -Demonstration of
operculated eggs.
• TREATMENT, PREVENTION AND
CONTROL
– Praziquantel – 25mg /kg body wt TID
for 1 day.
– Prevention of water pollution.
– Destruction of snails

40. Paragonimus westermani
(Lung Fluke)
• Oriental lung fluke
• Discovered in lungs of Bengal tigers in 1878 by
Kerbert
• Most commonly encountered in parts of Asia,
Africa and South America.
• Endemic in India  Assam, Bengal, Tamil Nadu &
Kerela.
• Reddish brown oval worm
• 10mm length, 5mm breadth and 4 mm thickness

41. • Definitive Host:
– Man,
– Cat
– Dog
– Fox
– Tiger
– Leopard and
– Monkey
• Intermediate Host
– 1st Int host
• Freshwater snail
– 2nd Int host
• Freshwater crayfish or a
Crab

44. Pathogenesis
• Migrate by penetrating through the intestinal wall 
peritoneal cavity abdominal wall  diaphragm 
lungs.
• Immature worms settle close to the bronchi  grow 
sexually mature hermaphrodite worms  eggs

45. Pathogenesis
• Inflammatory reaction to the worms & eggs  granuloma
formation, cystic dilation of bronchi, abscesses and pneumonitis.
• Cough with chest pain and haemoptysis
• Blood-stained rusty brown sputum
• Sputum contain yellowish brown eggs of parasite.
• Chronic case may be misdiagnosed as TB.

46. Clinical features
• Sometimes migrating larva
lose their way and are lodged
in ectopic sites such as
– liver,
– peritoneum,
– mesenteric lymph nodes,
– brain,
– heart and
– subcutaneous tissues of groin.
•Headache,
•Fever,
•Paralysis and
•Convulsive seizures when
parasites lodge in brain or
spinal cord.

47. DIAGNOSIS
• Symptoms
• History of eating improperly
cooked crab-meat in endemic
areas
• Eggs in the sputum
• ELISA
• Intradermal test