Virology is the scientific study of biological viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host cells for reproduction, their interaction with host organism physiology and immunity,

2. Characteristics
⦿Flat or fleshly, leaf-like unsegmented body.
⦿Incomplete alimentary canal.
⦿ Possess suckers with no hooks.
⦿Sexes are separate in Schistosomes, while the
others are hermaphroditic.
⦿ Oviparous

3. General Characteristics
⦿ Presence of two suckers.
⦿Has no body cavity, circulatory and
respiratory organs.
⦿ Alimentary system- mouth surrounded by
an oral sucker, muscular pharynx,
oesophagus which bifurcates into 2 blind
caeca (inverted Y shaped)
⦿Rudimentary nervous system – paired
ganglion cells.

5. Classification
BASED ON HABITAT:
⦿ BLOOD FLUKES
⦿ LIVER FLUKES
⦿ INTESTINAL FLUKES
⦿ LUNG FLUKES

6. Blood Flukes
⦿ Family : Schistosomatidae
⦿Genus : Schistosoma
⦿ Species:
1. S. haematobium
2. S. mansoni
3. S. japonicum
4. S. mekongi
5. S. intercalatum

7. SCHISTOSOMES
⦿ Schistosomiasis (bilharziasis)
⦿ Water-borne disease (Africa, Asia & Latin America).
⦿ Male worm is broader & lateral border is rolled
ventrally into a cylindrical shape, producing a long
groove – GYNECOPHORIC CANAL, inwhich
females are held.
⦿ Live in venous plexus in body of definitive host

8. Characteristics
⦿ Dioecious
⦿ Males are shorter and stouter than females
⦿ Lateral margins of males are folded ventrally to form a
gynecophoral canal in which females are received
⦿ Suckers are armed with delicate spines
⦿ There is no muscular pharynx
⦿ Eggs are non-operculated
⦿ Eggs are fully embryonated when laid
⦿ Embryonated eggs have a ciliated embryo called miracidium
⦿ Cercariae have bifid tails
⦿ There is no encysted metacerciarial stage
⦿ Infective Stage: cercaria penetrating the unbroken skin

9. Blood Flukes: Schistosomas
⦿Schistosoma japonicum: Oriental blood fluke
⦿Schistosoma haematobium: Vesical blood
fluke
⦿Schistosoma mansoni: Manson’s blood fluke

10. Features distinguishing Schistosomes
from other trematodes
⦿ Unisexual.
⦿Lack muscular pharynx
⦿Intestinal caeca reunite after bifurcation to
form a single canal.
⦿Produce non-operculated eggs.
⦿Cercariae have forked tails and infects by
penetrating unbroken skin of definitive
host.

11. SCHISTOSOMA HAEMATOBIUM

12. HISTORY & DISTRIBUTION
⦿ Bilharzia haematobium.
⦿ Bilharz described about the adult worm.
⦿Endemic in most parts of Africa, West Asia
some parts of India.

13. MORPHOLOGY

14. ADULT WORM FEMALE
20mm long,
0.25mm thick with
cuticular tubercles
confined to ends.
GYNECOPHORIC
CANAL
MALE
10-15mm long, 1mm
thick & covered by
finely tuberculated
cuticle
SUCKERS

15. EGG
Ovoid non-operculated Gravid worm has
20-30 eggs in
uterus at a time &
realises 300
Eggs/day
With a brownish yellow
transparent shell
carrying terminal spine
at one pole

16. Life Cycle
⦿ Definitive host : Humans
⦿ Intermediate host : freshwater snails
⦿Infective form : Cercaria larva

19. Clinical Features
⦿Classified Depending On Stages In
Evolution Of Infection:
o During Incubation Period
o During Oviposition
o During Tissue Proliferation & Repair

20. 1.Skin penetration & Incubation period
⦿ Local cercarial
dermatitis/Swimmer’s itch –
transient itching and petechial
lesions at site of entry of cercariae.
o Often in visitors to endemic
areas than locals
⦿ Anaphylactic or toxic
symptoms – fever, malaise and
urticaria.
⦿ Accompanied by leucocytosis,
eosinophilia, enlarged tender liver

21. 2.Oviposition
⦿Painless terminal hematuria – initially microscopic
later becomes gross.
⦿Develops frequency of micturition and burning.
⦿Cystoscopy – hyperplasia and inflammation of
bladder mucosa.

22. 3.Tissue proliferation and repair
⦿ Generalised hyperplasia & fibrosis of vesical mucosa with
granular appearance – sandy patch.
⦿ Pseudo abscesses – d/t dense infiltration with
inflammatory cells at site of deposition of eggs.
⦿ Chronic cystitis – secondary bacterial infection.
⦿ Calculi formation d/t deposition of oxalate & uric acid
crystals around eggs.
⦿ Obstructive hyperplasia of ureters & urethra.
⦿ Associated Squamous cell carcinoma.

23. Lab Diagnosis
⦿ Detection of egg:
o Urine microscopy
o Bladder mucosal biopsy
⦿ Detection of antigen:
o Circulating anodic antigen & Circulating cathodic antigen by
ELISA
⦿ Detection of antibody:
o Complement Fixation Test (CFT)
o Immunofluorescence
o Indirect Hemagglutination
o Bentonite flocculation test
o Enzyme linked immunoelectrotransfer blot
o FAST/ELISA

24. ⦿ Intradermal skin test(Fairley’s test):
o Group specific test gives positive
to all Schistosomiasis
⦿ Imaging:
o X-Ray- bladder and ureteral
calcification.
o USG-hydroureter & hydronephrosis
o Indirect diagnosis: IVP & Cystoscopy

25. Treatment & Prophylaxis
⦿ DOC – Praziquantel (40mg/kg for 1 day)
⦿Alternative DOC – Metriphonate
⦿ Prophylaxis:
o Eradication of intermediate molluscan hosts.
o Prevention of environmental pollution with urine and
faeces.
o Effective treated of infected.
o Avoid swimming, bathing and washing in infected water.

26. SCHISTOSOMA MANSONI

27. HISTORY & DISTRIBUTION
⦿Manson discovered eggs with lateral spines in the feces
of a west indian patient that led to the recognition of
this second species of human schistosomes.
⦿It is widely distributed in Africa, South America and
the Carribean islands.

28. HABIT MORPHOLOGY
⦿ Adult worm lives in the
inferiormesentericvein.
⦿ S. mansoni resembles S.
haematobium in
morphology and life cycle,
except:
⚫ Adult worms are smaller
and their integuments
studded with prominet
carse tubercles.
⚫ The prepatent period is 4-5
weeks.

29. Life Cycle
⦿ DEFINITIVE HOST: Humans are the only natural
definitive hosts.
⦿INTERMEDIATE HOST: Planorbid freshwater
snails of the genus Biomphalaria.
⦿ INFECTIVE FORM: Fork-tailed cercaria.

30. PathogenicityAnd Clinical Features
⦿ CERCARIAL DERMATITIS:
⚫Following skin penetration by cercariae
⦿ KATAYAMA FEVER:
⚫Formation of immune complexes. Signs and symptoms
include high fever, rash, arthralgia, etc..
⦿ INTESTINAL BILHARZIASIS:
⚫Microabscesses.
⚫Portal hypertension.

31. Laboratory Diagnosis
⦿ Stool microscopy.
⦿Rectal biopsy.
⦿ Serological diagnosis.
⦿ Imaging.
⦿Blood examination.

32. TREATMENT & PROPHYLAXIS
⦿ DOC – Praziquantel (40mg/kg for 1 day)
⦿Oxamniquine(single oral dose 15mg/kg) is
also effective.
⦿ Prophylaxis:
o Eradication of intermediate molluscan hosts.
o Prevention of environmental pollution with urine and
faeces.
o Effective treated of infected.
o Avoid swimming, bathing and washing in infected
water.

33. SCHISTOSOMA JAPONICUM

34. ⦿ COMMON NAME: Oriental blood fluke
⦿DISTRIBUTION: Far east, Japan, China..
⦿HABITAT: superior mesenteric vein, also seen
in the intrahepatic portal venules and
hemorrhoidal plexus of veins
⦿ MORPHOLOGY:
⚫Adult male is comparatively slender(0.5mm
thick).
⚫Female lays upto 3500 eggs at one time.
⚫The prepatent period is 4-5 weeks.
⚫Eggs are smaller as compared to S.
haematobium and S. mansoni.

35. LIFE CYCLE
⦿Similar to S. haematobium, except;
⚫DEFINITIVE HOST: man
⚫INTERMEDIATE HOST: Amphibian snails of
the genus Oncomelania.
⚫INFECTIVE FORM FOR HUMAN: Fork
tailed cercaria.

36. PATHOGENICITYAND CLINICAL FEATURES
⦿ Katayama Fever.
⦿ Chronic Illness.
⦿Central Nervous System and Lungs Involved.

37. TREATMENT & PROPHYLAXIS
⦿ DOC – Praziquantel (40mg/kg for 1 day)
⦿ Prophylaxis:
o Eradication of intermediate molluscan hosts.
o Prevention of environmental pollution with
urine and faeces.
o Effective treated of infected.
o Avoid swimming, bathing and washing in
infected water.

38. Schistosoma Intercalatum
⦿First noted in 1934 in West-Central Africa.
⦿Eggs are fully embryonated without any operculum.
Eggs are acid-fast.
⦿Produces few symptoms involveing the mesentric
portal system.
⦿Diagnosis is established by detecting the egg in
feces and rectal biopsy.
⦿Praziquantel is the drug of choice.

39. Schistosoma Mekongi
⦿ First recognized in 1978 is found in Thailand and
Cambodia along the Mekong river.
⦿ Closely related to S. japonicum but is slightly
smaller and round.
⦿ Man and dog are the definitive host.
⦿ Man acquires infection in the same way as in S.
japonicum.
⦿ Hepatosplenomegaly and ascites are the common
clinical finding.

40. HERMAPHRODITIC FLUKES:
LIVER FLUKES

41. Fasciola Hepatica
⦿ COMMON NAME: Sheep liver fluke.
⦿ HISTORY & DISTRIBUTION:
⚫ First trematode that was found more than 600
years ago in 1379 by Jehan de brie.
⚫ Named by Linnaeus in 1758.
⚫ Largest and most common liver fluke.
⚫ Cause economically important disease “liver rot” in
sheep.
⚫ F.gigantia is more prevalent in india than
F.hepatica.
⦿ HABITAT: parasite resides in the liver and
biliary passages of the definitive host.

42. ⦿ MORPHAOLOGY:
⚫ Large in size, flat leaf-shaped fluke measuring 30mm long
and 15mm broad, gray or brown in color.
⚫ Adult worm lives 5 years in sheep and 10 years in
humans.
⚫ Has a conical projection anteriorly containing an oral
sucker and is rounded posteriorly.
⚫ EGG:
○ Are large, ovoid, operculated,bile-stained and about
140µm by 80µm in size.
○ Contain an immature larva, the miracidium.
○ Do not float in saturated solution of common salt.
○ Eggs of F.hepatica and Fasciolopsis Buski cannot be
differentiated.
○ Eggs are unembryonated when freshly passed.

44. LIFE CYCLE

46. PATHOGENICITY
⦿ Acute Or Invasive Phase
⚫ Period during which the fluke migrates from the
intestine to the liver and its burrowing through the
liver parenchyma.
⚫ No significant change from the intestine to the liver
⚫ Parasite may wander or be carried by blood after
penetrating a blood vessel to ectopic sites such as
lungs, subcutaneous Tissues, brain and the orbit.
⚫ Abscesses or fibrotic lesions Migration to the liver
parenchyma.
⚫ Traumatic and necrotic lesions.

47. ⦿ Chronic Or Latent Phase
⚫ period when the parasite has already reached the bile
ducts
⚫ obstruction in the vessel
⚫ inflammatory and adenomatous changes of the biliary
epithelium
⚫ fibrosis of the ducts
⚫ pressure atrophy of the liver parenchyma
⚫ intensive periductal fibrosis
⚫ Heavy infections
○ erosion of the epithelium
○ young worms wander back into the liver to produce
abscess pockets and to seed the vital liver tissue with their
eggs

48. DIAGNOSIS
⦿Clinical-based on:
○ Biliary symptoms.
○ Moderate to high eosinophilia.
○ Eating watercress as a green
salad(metacercaria in vegetation)
⦿ Laboratory
○ Recovery of the eggs in the patient’s stool or
from duodenal or biliary tract drainage.
○ Serodiagnosis-helpful but not adapted
for routine diagnosis.

49. TREATMENTAND PROPHYLAXIS
⦿ Oral triclabendazole(10mg/kg once) is the
treatment of choice.
⦿ Alternative drug is bithionol(30-50mg for 10-
15days).
⦿ Prednisolone at a dose of 10-20mg/kg is used to
control toxemia.
⦿ PHROPHYLAXIS
⚫ Health education.
⚫ Control of snails.
⚫ Proper disposal of human, sheep and cattle feces.
⚫ Proper disinfection of watercresses and other water
vegetations before consumption.

50. DICROCOELIUM DENTRITICUM
⦿Morphology
⚫ slender, lancet shaped, flat transparent, aspinous body 5 to 15 mm
by 1.5 to2.5 mm
⚫ Acetabulum lies at the beginning of the second fifth of the
body
⚫ two large, slightly lobed testes situated obliquely to each other
anterior to the small subglobose ovary just behind the ventral
sucker
⚫ voluminous uterine coils in the posterior thirds of the worm
⚫ Subglobose ovary lies to the right of the midline and
somewhat anterior to the equator of the worm
⚫ discrete vitelline follicles occupy lateral fields in the middle of
the body.
⚫ Eggs are deep golden-brown thick shelled, distinctly
operculated, measuring38 to 45u by 22 to 30u containing a fully
developed miracidium.

51. LIFE CYCLE

52. TREATMENTAND PROPHYLAXIS
⦿ Praziquantel -25 mg per kg TID for 2
consecutive days
⦿ PROPHYLAXIS:
⚫ no effective measures of control
⚫ Fresh herbs collected from grazing areas for use as food
for humans should be washed to remove the ants.

53. CLONORCHIS SINENSIS
⦿COMMON NAME: Chinese liver fluke
⦿HABITAT: Biliary tract and sometimes
pancreatic duct.
⦿ MORPHOLOGY:
⚫ADULT WORM:
○ 10-25mm long and 3-5mm broad.
○ Can survive for 15 years in biliary tract.
⚫EGGS:
○ Flask shaped, 35µm by 20µm with a yellowish
brown shell.

54. LIFE CYCLE

55. PATHOLOGY
⦿ Distal bile ducts are irritated mechanically and by its
toxic secretions
⦿ Slight leukocytosis and eosinophilia in early infection
⦿ Enlarged tender liver
⦿ Bile ducts thicken and become dilated and tortuous
⦿ Adenomatous proliferation of the biliary epithelium
⦿ Fibrosis and destruction of hepatic parenchyma
⦿ Liver function is impaired although SGPT and SGOT are
normal

56. DIAGNOSIS
⦿ CLINICALDIAGNOSIS
⚫ Suggestive in patients
from endemic areas with:
○ History of eating uncooked
fish.
○ Symptoms of biliarytract
disease
- intermittent jaundice
- bouts of fever
- right upper quadrant pain
⦿ LABORATORY
DIAGNOSIS
⚫ Finding the
characteristic eggs in
the feces or biliary
drainage or duodenal
aspiration.
⚫ Eggs to be
differentiated from
opistorchid and
heterophyid flukes.

57. TREATMENTAND PROPHYLAXIS
⦿ Praziquantel -25 mg per kg TID for 2
consecutive days
⦿ PROPHYLAXIS:
⚫ Proper cooking of fish.
⚫ Proper disposal of feces.
⚫ Control of snails.

58. INTESTINAL FLUKES

59. FASCIOLOPSIS BUSKI
⦿ COMMON NAME: Giant intestinal fluke.
⦿ First described by busk in 1843.
⦿ HABITAT: Duodenum or jejunum of pigs and man.
⦿ MORPHOLOGY:
⚫ Largest fluke. Thick, fleshy, ovate.Flesh-coloured. 2-7.5
x 1-2 cm.
⚫ Oral sucker and ventral suckers present.Typical trematode
alimentary canal with unbranched intestinal caeca.
⚫ Two dendritic testes.
⚫ Single branched ovary.
⚫ Vitellaria on lateral sides and a convoluted uterus and
genital pore that is anterior to theventral sucker.
⦿ EGG: Yellowish and oval. 130-140 x 80-85 μ
.
Thin walled
with small operculum. Undeveloped ovum.

60. PATHOLOGY
⦿ Attached to intestine by suckers.
⦿ Mucosa inflamed, ulcerated and abscesses
form. Epigastric pain, nausea, diarrhoea.
⦿ Heavy infection leads to oedema, ascites and
anarsaca.
⦿ Toxic products of worm.
⦿ Anaemia, leukocytosis, lymphocytosis, and
esinophilia.
⦿ Good prognosis if worm treated early.
⦿ 1000-2000 worms affect intestinal secretions
and food passage and
⦿ intoxication and sensitization.

61. LIFE CYCLE

62. DIAGNOSIS, TREATMENTAND
PROPHYLAXIS
⦿ DIAGNOSIS:
⚫ Eggs in feces. Differentiate from F.hepatica, Gastro discoides
and Echinostoma sp.
⦿ Adult worms vomited or passed in stool.
⦿ TREATMENT:
⚫ Praziquantel(15 mg/kg) body weight, single dose is the drug of
choice .
⦿ PROPHYLAXIS:
⚫ Sanitary disposal of human feces.
⚫ Discourage use of night soil.
⚫ Restrict pigs.
⚫ Snail control.
⚫ Health education.
⚫ Cooking or steeping of water plants.

63. HETEROPHYES HETEROPHYES
⦿ MORPHOLOGY:
⚫ Pyriform, greyish, 1.3 x 0.5 mm.Oral, Ventral and Genital suckers.
⦿ EGG:
⚫ Light brown in colour, thick shell, operculated, 29 x 16μm,Fully
developed miracidium.
⦿ TREATMENT:
⚫ Praziquantel(15 mg/kg) body weight, single dose is the drug of
choice .
⦿ PROPHYLAXIS:
⚫ Sanitary disposal of human feces.
⚫ Discourage use of night soil.
⚫ Restrict pigs.
⚫ Snail control.
⚫ Health education.
⚫ Cooking or steeping of water plants.

64. METAGONIMUS YOKOGAWAI
⦿ MORPHOLOGY:
⚫ Small, 1.4 x 0.6 mm. Pyriform shape with rounded posterior
and tapering anterior. Large ventral sucker.
⦿ EGG:
⚫ Light yellow-brown, thin-shelled, operculated, 28x17 μm,
mature miracidium.
⦿ TREATMENT:
⚫ Praziquantel(15 mg/kg) body weight, single dose is the drug of
choice .
⦿ PROPHYLAXIS:
⚫ Sanitary disposal of human feces.
⚫ Discourage use of night soil.
⚫ Restrict pigs.
⚫ Snail control.
⚫ Health education.
⚫ Cooking or steeping of water plants.

65. LUNG FLUKES

66. PARAGONIMUS WSTERMANI
⦿ Common name: Oriental lung fluke
⦿ History and Distribution:
⚫ P.westermani was discovered in 1878 by Kerbert in
the lungs of Bengal tigers that died in the zoological
gardens at Hamberg and Amsterdam.
⚫ The parasite is endemic in the Far East—Japan,
Korea, Taiwan, China, and south east asia—Sri Lanka
and India. Cases have been reported from Assam,
Bengal, TamilNadu, and Kerala.
⚫ P.mexicanus is an important human pathogen in
Central and South America.

67. MORPHOLOGY
ADULT WORM:
⦿ The adult worm is egg-shaped about 10 mm long,
5 mm
⦿ broad and 4 mm thick and reddish brown in color.
⦿ The integument is covered with scale like spines.
⦿ It has 2 unbranched intestinal caeca which end
blindly in the caudal area.
⦿ They have a lifespan of up to 20 years in humans.
EGG:
⦿ The eggs are operculated, golden brown in color and
about 100μm by 50μmin size.
⦿ They are unembryonated when freshly laid.

68. LIFE CYCLE

69. CLINICAL FEATURES, DIAGNOSIS,
TREATMENTAND PROPHYLAXIS
⦿ Clinical features:
⚫ Peribronchial granuloma and cystic dilation of
bronchi. Dyspnea, hemoptysis, pneumonitis,
bronchiectasis, abcess, pneumothorax.
Extrapulmonary lesions in brain and intestine.
⦿ Diagnosis:
⚫ Ova in sputum, X-ray and CT scan of chest, CFT, IHA,
and ELISA.
⦿ Treatment:
⚫ Praziquantel is the drug of choice.
⦿ Prophylaxis:
⚫ Adequate cooking of crabs and crayfish, eradication of
molluscan hosts and treatment of infected persons.

70. THANK YOU