Clinical Parasitology: Platyhelminthes: Trematodes

A comprehensive vocabulary flashcard set based on the lecture notes covering trematode classification, lifecycle stages, morphology, and specific species characteristics of blood, lung, intestinal, and liver flukes.

Trematodes

Dorso-ventrally flattened, unsegmented, leaf-like, and hermaphroditic flatworms (except blood flukes) with an incomplete digestive tract and two radially striated suckers.

Acetabula

Muscular suckers found on the oral or ventral surface of the flukes.

Cercaria

The final developmental stage in the snail host, consisting of a body with a tail that aids it in swimming after leaving the snail.

Digenea

A subclass of Trematoda within the phylum Platyhelminthes.

Metacercaria

The encysted resting stage for hermaphroditic flukes that occurs when a cercaria sheds its tail and secretes a protective wall; it is the infective stage for humans.

Miracidium

The ciliated first-stage, free-swimming larva of a trematode that emerges from the egg and must penetrate a snail host to continue its life cycle.

Redia

The second or third larval stage in the snail host that develops within a sporocyst; these are elongated, saclike organisms with a mouth and a gut.

Schistosoma

A genus of Digenea, commonly called blood flukes, which are dioecious and found in mating pairs in the blood vessels of their definitive host.

Schistosomula

The immature schistosome in human tissues that develops from the cercaria after it has lost its tail during skin penetration.

Sporocyst

A simple saclike larval form containing germinal cells that develops from a miracidium in the snail intermediate host.

Gynecophoral canal

A ventral fold formed by the lateral margins of male blood flukes where the female resides during copulation.

Schistosoma japonicum

Commonly known as the Oriental blood fluke, it resides in the superior mesenteric veins and produces between $500$ and $2000$ eggs per day.

Schistosoma haematobium

Commonly known as the Vesical blood fluke, found in the pelvic venous plexus of the bladder; it utilizes Bulimus snails as an intermediate host.

Schistosoma mansoni

Commonly known as Manson’s blood fluke, often found in the inferior mesenteric veins draining the large intestine.

Katayama Fever

A systemic hypersensitivity reaction to migrating schistosomulae characterized by easy fatigability, respiratory symptoms, fever, and eosinophilia, typically occurring $2$ to $12$ weeks after penetration.

Paragonimus westermani

Known as the Oriental Lung Fluke, it is a reddish-brown, coffee bean-shaped hermaphroditic fluke measuring $4 ext{--}6\,mm$ in width.

Brotia asperata

The first intermediate snail host for Paragonimus westermani in the Philippines where the miracidium develops into sporocysts and rediae.

Sundathelpusa philippina

The second intermediate host (crab) for Paragonimus westermani that harbors the infective metacercaria.

Fasciolopsis buski

The Giant intestinal fluke, which is unbranched and measures $20 ext{--}75\,mm$ in length, infecting humans and pigs through aquatic plants.

Echinostoma ilocanum

Commonly known as Garrison’s fluke, characterized by a horse-shaped collar of $49 ext{--}51$ spines around the oral sucker.

Pila luzonica

A second intermediate host (kuhol) for Echinostoma ilocanum.

Heterophyes heterophyes

A small intestinal fluke measuring less than $2\,mm$ with scale-like spines and occasionally a gonotyl (genital sucker).

Metagonimus yokogawai

The smallest human fluke, which resides in the small intestine and has a ventral sucker (genitoacetabulum) situated off-center.

Fasciola hepatica

Known as the Sheep Liver Fluke or Temperate Liver Fluke, possessing a prominent cephalic cone and highly branched intestinal caeca.

Fasciola gigantica

The Giant Liver Fluke or Tropical Liver Fluke, which is more lanceolate and is the dominant species affecting livestock in the Philippines.

Triclabendazole

The recommended drug of choice for treating Fascioliasis.

Clonorchis sinensis

Known as the Chinese or Oriental Liver Fluke, its eggs are electric bulb-shaped with a convex operculum and visible shoulders.

Parafossarulus manchouricus

The most common snail host for the liver fluke Clonorchis sinensis.

Eurytrema pancreaticum

The pancreatic fluke, which humans accidentally ingest via the second intermediate host, the ant Technomyrmex deterquens.

Praziquantel

The standard treatment drug for most trematodes, often prescribed at a dosage of $25\,mg/kg$ for multiple doses.