MLS 042 - P2 W3: Overview of Trematodes & Liver Flukes

First intermediate host of ALL trematodes

Freshwater or Land Snail (Always a mollusk)

Only trematode that is DIOECIOUS (separate sexes)

Schistosoma spp. (Blood fluke)

Only trematodes with NON-OPERCULATED eggs with spines

Schistosoma spp.

Infective stage of all ORGAN-dwelling flukes

Metacercaria (encysted larva on plant or freshwater fish/crab)

Infective stage of BLOOD flukes (Schistosoma)

Cercaria (direct skin penetration in water - no 2nd IH)

Trematodes with MATURE eggs (contains miracidium) at oviposition

Schistosoma, Clonorchis, Opisthorchis, Heterophyids

Trematodes with IMMATURE eggs (unembryonated) at oviposition

Fasciola, Fasciolopsis, Paragonimus, Echinostoma

Fluke family possessing a third sucker called a GONOTYL

Heterophyids (Genital sucker)

Specimen of choice: DUODENAL DRAINAGE

Clonorchis sinensis & Opisthorchis spp.

Specimen of choice: SPUTUM

Paragonimus westermani (Lung fluke)

Specimen of choice: URINE

Schistosoma haematobium

Fasciola hepatica common name and disease

Sheep liver fluke / Temperate liver fluke (Sheep liver rot / Fascioliasis)

Fasciola hepatica adult diagnostic morphology

Cephalic cone with DISTINCT SHOULDERS and converging lateral margins

Fasciola gigantica common name and dominant region

Giant / Tropical liver fluke (Dominant in cattle and carabaos in the Philippines)

Fasciola gigantica adult morphology

Larger size, longer cephalic cone, LESS developed shoulders, and PARALLEL margins

Fasciola spp. 1st intermediate host

Lymnaea snails (L. philippinensis, L. swinhoe, L. truncatula)

Fasciola spp. 2nd intermediate host

Aquatic plants / vegetation (Watercress, grass, kangkong / Ipomoea reptans)

Fasciola egg morphology

Large (128-150 x 60-90 um), yellowish-brown, operculated, mass of unsegmented yolk cells

DRUG OF CHOICE for Fasciola (Praziquantel is INEFFECTIVE)

Triclabendazole (10 mg/kg single dose)

Dicrocoelium dendriticum common name and morphology

Lancet fluke (Small, thin, smooth lanceolate body with NO spines)

Dicrocoelium dendriticum intermediate hosts

1st IH: Land snail (Zebrina, Cionella) in slime balls / 2nd IH: Ants (Formica spp.)

Fluke whose metacercaria lodges in the SUBESOPHAGEAL GANGLION altering ant behavior

Dicrocoelium dendriticum (Lancet fluke)

Clonorchis sinensis common name and distribution

Chinese liver fluke (East Asia: China, Korea, Japan, Vietnam)

Clonorchis sinensis egg appearance

Old-fashioned electric bulb shape (Distinct opercular shoulders and abopercular knob)

Clonorchis sinensis adult sucker ratio

Ventral sucker is smaller than the oral sucker

Clonorchis sinensis intermediate hosts

1st IH: Parafossarulus / Bithynia snail / 2nd IH: Grass carp (Ctenopharyngodon idellus)

Opisthorchis felineus common name and primary host

Cat liver fluke / Siberian liver fluke (Europe, Russia, Siberia - Cats are main host)

Opisthorchis viverrini common name and distribution

Southeast Asian liver fluke (Thailand, Laos, Cambodia, Vietnam)

Fluke with the HIGHEST RISK of CHOLANGIOCARCINOMA (Bile duct cancer)

Opisthorchis viverrini (Very prevalent in Northeast Thailand)

Standard Drug of Choice for Clonorchis and Opisthorchis

Praziquantel (25 mg/kg PO TID x 1-2 days)

Type of gallstones formed due to chronic liver fluke infection

Brown pigment stones (caused by biliary stasis and epithelial irritation)

Mnemonic: C-F-V

C = Clonorchis (China) / F = felineus (Felines-Cats) / V = viverrini (Vietnam, Very cancerous)