Clinical Parasitology - Trematodes | Lecture notes Parasitology

TREMATODES (FLUKES)

General classification

• Snail as first IH

• Adult: Leaf-like structure

• Requires 2 IH

• Second IH: other snail, fish, crab, vegetable,

ants

• Operculated egg (may takip)

• Mnemonics: SHOCE for embryonated ova

(miracidium), mature ova

o S – Schistosoma (blood fluke)

o H – Heterophyids (intestinal fluke)

o O – Opisthorchis (liver fluke)

o C – Clonorchis sinensis (liver fluke)

o E – Eurytrema pancreaticum (pancreatic

fluke)

• Distinctive characteristics

o Collar spine: Echinostoma ilocanum

(Garrison’s fluke)

▪ Horseshoe-like appearance

▪ First & second IH are both snails (pag

first IH ang na-ingest, hindi maiinfect)

o Intestinal Ceca

▪ Simple

▪ Branched/dendritic

o Testes

▪ Tandem (magkadikit) – Fasciola

▪ Oblique (magkahiwalay) – Opisthorchis

▪ Branched: Fasciola/Fasciolopsis

o Cephalic Cone

▪ Adult Fasciola (may shoulder)

▪ Ova Clonorchis (may shoulder)

o Gonotyle

▪ Genital sucker – Heterophyes

heterophyes (tatlo yung suckers: oral,

ventral, genital)

o Adult

▪ Cylindrical/elongated – Schistosoma

▪ Male Schistosoma – gynecophoral canal

(for female); copulation: 24hrs

• Three Chief classes of Platyhelminths

o Turbellaria – free-living

o Trematoda – parasitic and known as

‘flukes’, leaf-like.

o Cestoda – parasitic and known as

‘tapeworms’; Segmental (scolex, neck, body)

• Life cycle of trematodes

o Egg

▪ Operculated (except Schistosomes)

o Larva

▪ Mnemonics : Ma’am Sheila loves Red Car

Mazda

▪ M – Miracidium

▪ S – Sporocyst

▪ R – Redia

▪ C – Cercaria

▪ M – Metacercaria

• Two classifications of Trematodes

o Blood flukes

▪ Schistosoma spp.

o Non-blood flukes

▪ Liver fluke

▪ Intestinal gluke

▪ Lung fluke

▪ Pancreatic fluke

BLOOD FLUKES

o Schistosoma japonicum

o Schistosoma mansoni

o Schistosoma haematobium

o Schistosoma mekongi

o Schistosoma intercalatum

Differences between Schistosoma spp.

Feature

japonicum

mansoni

haematobi

Oriental

blood fluke

Manson’s

blood fluke

Vesicular

fluke

Testes

6 – 7,

single file

8 – 9,

zigzag row

4 – 5, in

groups

Ovary

50 or more

eggs;

middle

1 – 3 eggs;

middle

20 – 30

eggs;

behind

middle

Intestine

short

longest

Long

Egg

Lateral

knob

Lateral

spine

Terminal

spine

Oncomela

nia

Biomphala

ria and

Australorbi

Bulimus

(Physopsis

)

Human &

domestic

animals

Human

Specim

en of

Choice

Blood &

stool

Blood &

stool

Blood &

urine

• General morphology

o Egg – circular, elongated, knob-like/spine.

o Larva

▪ Cercaria possess bifid tail (two-tailed).

▪ No metacercaria

▪ Infective stage – CERCARIA

▪ MOT: Skin penetration

▪ Miracidium

• Alkaline clean water (25-31ºC)

• Free-swimming ciliated embryo

liberated from the egg.

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TREMATODES (FLUKES)

General classification

Snail as first IH
Adult: Leaf-like structure
Requires 2 IH
Second IH: other snail, fish, crab, vegetable, ants
Operculated egg (may takip)
Mnemonics: SHOCE for embryonated ova (miracidium), mature ova o S – Schistosoma (blood fluke) o H – Heterophyids (intestinal fluke) o O – Opisthorchis (liver fluke) o C – Clonorchis sinensis (liver fluke) o E – Eurytrema pancreaticum (pancreatic fluke)
Distinctive characteristics o Collar spine: Echinostoma ilocanum (Garrison’s fluke) ▪ Horseshoe-like appearance ▪ First & second IH are both snails (pag first IH ang na-ingest, hindi maiinfect) o Intestinal Ceca ▪ Simple ▪ Branched/dendritic o Testes ▪ Tandem (magkadikit) – Fasciola ▪ Oblique (magkahiwalay) – Opisthorchis ▪ Branched: Fasciola/Fasciolopsis o Cephalic Cone ▪ Adult Fasciola (may shoulder) ▪ Ova Clonorchis (may shoulder) o Gonotyle ▪ Genital sucker – Heterophyes heterophyes (tatlo yung suckers: oral, ventral, genital) o Adult ▪ Cylindrical/elongated – Schistosoma ▪ Male Schistosoma – gynecophoral canal (for female); copulation: 24hrs
Three Chief classes of Platyhelminths o Turbellaria – free-living o Trematoda – parasitic and known as ‘flukes’, leaf-like. o Cestoda – parasitic and known as ‘tapeworms’; Segmental (scolex, neck, body)
Life cycle of trematodes o Egg ▪ Operculated (except Schistosomes) o Larva ▪ Mnemonics : M a’am S heila loves R ed C ar M azda ▪ M – Miracidium ▪ S – Sporocyst ▪ R – Redia ▪ C – Cercaria ▪ M – Metacercaria
Two classifications of Trematodes o Blood flukes ▪ Schistosoma spp. o Non-blood flukes ▪ Liver fluke ▪ Intestinal gluke ▪ Lung fluke ▪ Pancreatic fluke BLOOD FLUKES o Schistosoma japonicum o Schistosoma mansoni o Schistosoma haematobium o Schistosoma mekongi o Schistosoma intercalatum Differences between Schistosoma spp. Feature S. japonicum

S.

mansoni

S.

haematobi um CN Oriental blood fluke Manson’s blood fluke Vesicular fluke Testes 6 – 7 , single file

zigzag row 4 – 5 , in groups Ovary 50 or more eggs; middle 1 – 3 eggs; anterior middle

eggs; behind middle Intestine short longest Long Egg Lateral knob Lateral spine Terminal spine IH Oncomela nia Biomphala ria and Australorbi s Bulimus (Physopsis ) DH Human & domestic animals Human Human Specim en of Choice Blood & stool Blood & stool Blood & urine

General morphology o Egg – circular, elongated, knob-like/spine. o Larva ▪ Cercaria possess bifid tail (two-tailed). ▪ No metacercaria ▪ Infective stage – CERCARIA ▪ MOT: Skin penetration ▪ Miracidium - Alkaline clean water (25- 31 ºC) - Free-swimming ciliated embryo liberated from the egg.

Infect snails ▪ Cercaria
Emerges from daughter sporocysts
Escapes from the snail
Has a body and forked tail
Infects man by skin penetration ▪ Schistosomule
Cercaria without tail
Develops from cercaria after skin penetration
Adapted to survive in serum or physiologic saline at 37ºC
Enter the pleural cavity>diaphragm>peritoneal space>penetrate the liver to reach the intrahepatic portions of the portal vein o Primarily parasites of portal vein and its branches o Female fluke: 500-2000 immature eggs/day o Embryonation: 10- 1 2 days
Pathogenesis o Schistosomiasis o Pneumonitis due to schistosomula in the lungs o Hepatosplenic disease o Colonic schistosomiasis o Cerebral schistosomiasis
Stool examination techniques o Merthiolate-Iodine Formalin Concentration Technique (MIFC) ▪ Sensitive for moderate and heavy infections ▪ Not adequate for light infections o Kato Katz technique ▪ For enumeration of eggs ▪ Most commonly used for evaluating epidemiology, effect of control measures, drug trials
Immunodiagnosis (blood) o Intradermal tests for immediate cutaneous hypersensitivity using adult worm extracts (skin) o Indirect hemagglutination using adult worm and egg antigens (IHA) o Cicrumoval precipitin test (COPT, Bleb test) o Enzyme-linked Immunosorbent Assay (ELISA) using soluble antigens of adults and eggs
Treatment o DOC: Praziquantel
Epidemiology o Sorsogon o Oriental Mindoro o Samar o Leyte o Bohol o All provinces in Mindanao, EXCEPT: Misamis Oriental LUNG FLUKE Paragonimus westermani
General morphology o Egg ▪ Yellowish brown ▪ Thick-shelled ▪ Operculated with a thickened abopercular end ▪ May be seen in the sputum or feces if the sputum is swallowed ▪ Charcot-leyden crystal o Adult ▪ Hermaphroditic ▪ Body covered with spines ▪ Reddish brown ▪ Measures 4-6 mm in width and 3.5-5 mm in thickness ▪ Resembles a coffee bean ▪ Found in pairs or in threes in fibrotic capsules or cysts in the lungs
Specimen of choice o Sputum o Stool
Intermediate hosts o First IH: Brotia asperata (snail) o Second IH: Sundathelpusa philippina (talangka)
Diagnosis o Radiographs o Definitive diagnosis: finding ova in the sputum, stool, or less frequently in aspirated material from abscesses or pleural effusions o Multi-dot ELISA
Pathogenesis & clinical manifestations o Paragonimiasis o Cough o Hemoptysis o Symptoms consistent with pulmonary tuberculosis o Misdiagnosed as Pulmonary Tuberculosis
Treatment o DOC: Praziquantel o Bithionol
Epidemiology o Global distribution o Philippines ▪ Leyte ▪ Sorsogon ▪ Mindoro ▪ Camarines ▪ Samar

o Metagonimus yokogawai o Haplorchis taichui o Haplorchis yokogawai

Many species live in the intestine of fish-eating hosts
MOT: ingestion of metacercariae encysted in fish
Metacercariae in the abdomen excysts, liberating a larva that attaches to the intestinal wall
General morphology o Egg ▪ Light brown ▪ Ovoid ▪ Operculated ▪ Fully developed symmetrical miracidium is already present ▪ Operculum fits into the egg smoothly ▪ No abopercular protruberance like that of Clonorchis sinensis ovum o Heterophyes heterophyes Adult ▪ Elongated ▪ Oval or pyriform ▪ Measures less than 2 mm in length ▪ Integument has fine scale-like spines ▪ Some species have gonotyl or genital sucker
Pathogenesis o Heterophyiasis o Inflammation at the site of attachment o Manifestations are consistent with the peptic ulcer (observed among infected individuals in Compostela Valley) ▪ Upper abdominal discomfort ▪ Gurgling abdomen
Diagnosis o Detection of eggs in the stool using Kato Katz method o Care must be taken to distinguish them from Clonorchis and Opisthorchis
Treatment o DOC: Praziquantel
Epidemiology o Egypt o Greece o Israel o Western India o Central and South China o Japan o Korea o Taiwan o Philippines ▪ Compostela Valley ▪ Mindanao

LIVER FLUKES

o Fasciola hepatica o Fasciola gigantica o Fasciola lanceolata o Clonorchis sinensis o Opisthorchis felineus Fasciola hepatica

CN: Sheep liver fluke, temperate liver fluke
General morphology o Egg ▪ Large ▪ Ovoid ▪ Operculated ▪ Bile stained ▪ Unsegmented o Adult ▪ Large, broad, flat body ▪ Anterior end forms a prominent cephalic cone ▪ Small oral and ventral suckers ▪ Long and highly branched intestinal caeca Fasciola gigantica
CN: Giant liver fluke, tropical liver fluke
General morphology o Egg ▪ Larger but very similar to Fasciola hepatica ova o Adult ▪ Larger than F. hepatica ▪ More lanceolate ▪ Less developed shoulders (shorter cephalic cone) ▪ Larger ventral sucker Fasciola spp. (F. hepatica & F. gigantica)
Intermediate hosts; o First IH ▪ Lymnea philippinensis o Second IH ▪ Watercress ▪ Grass
Pathogenesis o Fascioliasis o Right upper quadrant abdominal pain o Hypereosinophilia o Acute or invasive phase ▪ Migration from intestine to liver ▪ Traumatic and necrotic lesions in liver parenchyma o Chronic or latent phase ▪ Asymptomatic ▪ Parasite has reached the bile ducts

▪ Obstruction ▪ Stimulates inflammation in the biliary epithelium leading to fibrosis

Diagnosis o Microscopy o Serologic tests ▪ Low specificity because of cross reactivity with antigens of other parasites o RFLP ▪ PCR Restriction Fragment Length Polymorphism
Treatment o DOC: Bithionol o Triclabendazole
Epidemiology o Worldwide distribution o Economic importance in livestock raising o In Philippines ▪ The dominant species is Fasciola gigantica affecting cattle and water buffalos ▪ Few human cases are reported locally. Clonorchis sinensis
CN: Chinese liver fluke, Oriental liver fluke, Distome of China
General morphology o Egg ▪ Bile-stained ▪ Flask-shaped ▪ Operculated ▪ Contains a miracidium when oviposited ▪ Does not hatch in water but is ingested with a molluscan host ▪ Has a terminal spine ▪ Electric bulb in shape ▪ Infective to snails only o Adult ▪ Narrow, oblong, flat worm ▪ Oral sucker is slightly larger than the ventral sucker ▪ Blind intestinal caeca are simple and extend to the caudal region ▪ Life span is 20-30 years
Intermediate hosts o First IH ▪ Bulimus fuchsiana (snail not found in the Philippines) o Second IH ▪ Ctenopharyngondon idellus (fish)
MOT: consumption of raw undercooked fish and salted and dried fish harboring metacercariae
Pathogenesis o Clonorchiasis o Provokes intense proliferation of intestinal epithelium o Acute stage (less than 1 month of infection) ▪ Chills ▪ Fever o Chronic stage ▪ Cirrhosis ▪ Portal hypertension
Diagnosis o Detection of parasite egg in stool ▪ Clonorchis, Opisthorchis, and Heterophyid ova may not be differentiated under ordinary light microscope ▪ ELISA with crude Clonorchis sinensis antigen ▪ Enzyme immunoassay (EIA) ▪ Polymerase Chain Reactions
Treatment o Praziquantel
Epidemiology o Over 30 million people are infected in Southeastern Asia o No reported cases in children below 10 years old o Endemic in ▪ China ▪ Japan ▪ Korea ▪ Vietnam PANCREATIC FLUKE Eurytrema pancreaticum
CN: Pancreatic fluke
General morphology o Egg ▪ Operculated ▪ Thick shelled ▪ Dark brown ▪ Embryonated when laid o Adult ▪ Stout worm with ruffled margins ▪ Oral sucker is larger than the ventral sucker
Intermediate hosts o First IH ▪ Macrochlamys indica (snail) o Second IH ▪ Technomyrmex deterquens (ant)
Treatment o DOC: Praziquantel

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TREMATODES (FLUKES)

S.

S.

LIVER FLUKES