Trematodes: Morphology, Pathophysiology, and Diagnosis

All trematodes appear flat and leaf-like, except for schistosomes.
They all possess two suckers, except for Heterophyes heterophyes.
The oral sucker is used for nutrition, while the ventral sucker is used for attachment.
Heterophyes heterophyes has a genital sucker called a gonotyl.
Eggs are diagnostic, and are operculated except for Schistosoma.
The mode of transmission is ingestion, except for Schistosoma.

Fasciola spp., Clonorchis, and Opistorchis are liver flukes.
Fasciola spp. habitat is in the biliary passages of the liver.
The first intermediate host is Lymnaea spp., and the second intermediate host is aquatic plants.
Mode of transmission is ingestion of undercooked or raw aquatic plants containing the metacercaria.
Eggs are reported as Fasciola egg.
Fasciola hepatica is also known as the Sheep Liver Fluke, and Fasciola gigantica is known as the Tropical Liver Fluke.
Disease stages include acute and chronic stages, with symptoms of larval migration, worm maturation, and obstruction and inflammation leading to fibrosis or cirrhosis.

Clonorchis and Opistorchis are parasites of the bile duct and gallbladder.
They are fish-borne and have a habitat in the bile ducts and passages, pancreatic duct, and gallbladder.
Mode of transmission is ingestion of raw or undercooked fish containing the metacercaria.
Final host is humans.
Disease symptoms include fever, chills, fatigue, weight loss, liver enlargement, and jaundice.
Chronic infection leads to periductal fibrosis, cirrhosis, and portal hypertension.

Dicrocoelium dendriticum is a liver fluke, also known as the Lancet fluke.
Mode of transmission is ingestion of an ant.
Habitat is in the bile duct or liver.
First intermediate host is Citronella lubrica, and the second intermediate host is Formica fusca.
Final host is herbivores, with humans acting as accidental hosts.

Fasciolopsis buski is a giant intestinal fluke.
First intermediate host is Segmentiina, and the second intermediate host is water plants.
Mode of transmission is ingestion of encysted metacercaria from aquatic plants.
Adult worms have no cephalic cone, and intestinal ceca are simple and unbranched.
Disease symptoms include attachment to the small intestine, traumatic, obstructive, toxic, and malabsorption of vitamins.
Diagnosis is done through DFS, Kato Katz, and clinical impression.
Echinostoma ilocanum is a parasite of the small intestine, also known as Garrison's fluke.
First intermediate host is Gyraulus convexiusculus, and the second intermediate host is Pila luzonica and Vivipara angularis.
Mode of transmission is ingestion of metacercariae encysted in snails.
Adult worms have a circumoral disk with spines surrounding the oral sucker.
Disease symptoms include inflammation at the site of attachment, diarrhea, and intoxication.
Heterophyes heterophyes is a parasite of the small intestine, with a wide range of intermediate hosts (fish).
Mode of transmission is ingestion of encysted metacercariae in fish.
Habitat is in the small intestine.
Adult worms have a characteristic gonotyl.
Disease symptoms include local inflammation at the site of attachment.

Eurytrema pancreaticum is a pancreatic fluke.
Humans act as accidental hosts.
First intermediate host is Macrochlamys indica, and the second intermediate host is Technomyrmex deterquens.
Mode of transmission is ingestion of an ant or grasshopper.

Paragonimus westermani is an Oriental lung fluke.
Found in the sputum or feces, and embryonate in water.
First intermediate host is Antemelania asperata, and the second intermediate host is Sundathelphusa philippina (freshwater/mountain crab).
Mode of transmission is ingestion of undercooked crabs with metacercaria.
Reservoir hosts are dogs, cats, and rodents, and paratenic hosts are boars and pigs.
Adult worms have a reddish-brown, coffee bean-shaped body, and presence of spines on the tegument.
Disease symptoms include cough, blood-stained or rust-colored sputum, and pathology due to adult worms provoking a granulomatous reaction.
Diagnosis is done through microscopy, detecting eggs in stool or sputum.

Schistosoma spp. are blood flukes, with a mode of transmission through skin penetration.
Intermediate hosts are snails, and habitat is in the mesenteric veins or blood.
Worms ingest RBCs and possess hemoglobinase, breaking down globulin and hemoglobin.
Main pathology is caused by the egg.
Three species of Schistosoma are S. japonicum, S. mansoni, and S. haematobium.
S. japonicum is the Oriental blood fluke, with a habitat in the superior mesenteric vein.
First intermediate host is Oncomelania.
Eggs are oval with a recurved hook or knob.
Disease symptoms include dermatitis, pulmonary schistosomiasis, and acute phase Katayama syndrome.
S. mansoni is Manson's blood fluke, with a habitat in the inferior mesenteric vein.
First intermediate host is Biomphalaria.
Eggs are elliptical with a lateral spine.
Disease symptoms include intestinal bilharziasis, kidney damage, and nephrotic syndrome.
S. haematobium is the Vesical blood fluke, with a habitat in the vesical, prostatic, and uterine plexuses.
First intermediate host is Bulinus.
Eggs are elliptical with a terminal spine.
Disease symptoms include urinary bilharziasis, Egyptian hematuria, dysuria, and hematuria.