Veterinary Helminthology: Monogenea and Trematoda

Vocabulary practice flashcards covering veterinary helminthology, focusing on Monogenea and Trematoda classification, morphology, life cycles, clinical pathology, and treatments.

Opisthaptor

The posterior hooked attachment organ of monogenean parasites used to clamp firmly onto the gills, skin, or fins of cold-blooded aquatic or amphibious vertebrate hosts.

Monopisthocotylea

A major group of monogeneans characterized by a disc-shaped haptor armed with $1$ to $3$ pairs of central anchors (hamuli), transverse bars, and marginal hooklets rather than attachment clamps.

Polyopisthocotylea

A major group of monogeneans that primarily utilize complex clamp-like structures on their posterior haptor for attachment to their hosts.

Hamuli

Central hook-like anchors located on the haptor of monopisthocotylean monogeneans, supported by dorsal or ventral transverse bars or accessory sclerites for stabilization.

Gyrodactylidae

A family of small, elongate, viviparous monopisthocotyleans lacking eye spots, bearing a posterior haptor usually armed with $1$ pair of anchors and $16$ marginal hooklets, and reproducing via serial polyembryony.

Gyrodactylus elegans

A viviparous monopisthocotylean parasite of the skin, fins, and gills of various fish (common in trout) and frogs, capable of harboring up to $4$ nested generations within a single individual.

Dactylogyridae

A cosmopolitan family of oviparous freshwater monopisthocotyleans parasitizing cyprinids, characterized by $2$ pairs of eye spots and a haptor bearing $1$ or $2$ pairs of anchors and $12$ to $14$ marginal hooklets.

Dactylogyrus vastator

An oviparous monogenean parasitizing the gills of cyprinids, goldfish, pike, and trout; its reproduction and infection intensity peak in the warmest months, completing its life cycle in $1$ to $5\text{ days}$.

Dactylogyrus extensus

An oviparous gill monogenean of cyprinids capable of reproducing at lower temperatures than D. vastator, resulting in infection intensity rising throughout the winter.

Piping

A compensatory respiratory behavior in fish characterized by swimming to the water surface to gulp air, frequently seen when gill tissue is damaged and inflamed by monogenean infections.

Subclass Digenea

A subclass of trematodes with complex indirect life cycles requiring a mollusk first intermediate host and a vertebrate definitive host, possessing $2$ suckers and lacking attachment hooks.

Flame Cells

Ciliated specialized cells in the osmoregulatory tubular network of trematodes that beat fluid containing metabolic wastes (chiefly ammonia and urea) into excretory ducts.

Laurer's Canal

A canal in the female reproductive system of digenean trematodes arising near the seminal receptacle, functioning in copulation, sperm storage, or waste elimination during egg formation.

Mehlis' Gland

A female accessory reproductive gland surrounding the ootype in trematodes responsible for eggshell formation, eggshell hardening, and sperm activation.

Miracidium

The free-swimming, ciliated, non-feeding first larval stage of digenetic trematodes that hatches from an egg in water and penetrates a snail intermediate host.

Sporocyst

An undifferentiated sac-like larval stage of digeneans that develops from a miracidium within snail tissue, containing germinal cells that multiply to produce daughter sporocysts or rediae.

Redia

An intermediate digenean larval stage inside the snail host possessing an oral sucker, pharynx, simple sac-like intestine, excretory system, and a birth-pore for emerging cercariae.

Cercaria

A swimming digenean larval stage equipped with a tail, suckers, and an intestine that emerges from the snail host to encyst on vegetation or penetrate a second intermediate host.

Metacercaria

The encysted, infective resting larval stage of digenetic trematodes found on aquatic vegetation or inside second intermediate hosts that excysts upon ingestion by the definitive host.

Clinostomum complanatum

A digenean whose adults inhabit the mouth and throat of piscivorous birds (herons), whose metacercariae cause yellow cysts ('yellow grub') in freshwater fish, and which can cause accidental human laryngopharyngitis.

Apatemon gracilis

A strigeid fluke ($1.5$ to $2.5\,\text{mm}$ long) of pigeons and ducks whose cup-shaped anterior adhesive organ constricts intestinal villi, utilizing snails as first IH and leeches as second IH.

Black Spot Disease

A condition in cyprinid fish caused by encysted metacercariae of Posthodiplostomum cuticula in connective tissue, which induce host pigment cell deposition forming dark spots ($0.85$ to $3.8\,\text{mm}$ in diameter).

Posthodiplostomum minimum

A diplostomatid fluke whose metacercariae form non-pigmented white cysts ('white grub', $1\,\text{mm}$ in diameter) in the mesentery, liver, kidneys, pericardium, and spleen of freshwater fish.

Grey Pearl Disease

A condition in carp caused by the metacercariae of Neodiplostomum perlatum, which appear as small grey pearls within the skin, fins, muscles, and internal organs.

Diplostomum spathaceum

An eyefluke of piscivorous birds (gulls, terns) whose metacercariae inhabit the crystalline lens of freshwater fish, resulting in parasitic cataracts and impaired vision.

Alaria alata

An intestinal fluke ($2$ to $6\,\text{mm}$ long) of dogs, cats, foxes, and mink bearing two anterior ear-like tentacles, which develops an unencysted mesocercaria stage in tadpoles and paratenic hosts.

Mesocercaria

An unencysted, migrating larval stage of Alaria alata that is intermediate between the cercaria and metacercaria, occurring in second intermediate (frogs) or paratenic hosts.

Dicrocoelium dendriticum

The lancet fluke ($6$ to $10\,\text{mm}$ long), a spineless fluke inhabiting the bile ducts of ruminants with tandem lobed testes situated anterior to the ovary, utilizing land snails and Formica ants as intermediate hosts.

Slime Ball

A mucous mass containing $200$ to $400$ Dicrocoelium dendriticum cercariae expelled by infected land snails (Zebrina detrita or Cionella lubrica), which is ingested by secondary host ants (Formica spp.).

Eurytrema pancreaticum

A large fluke ($8$ to $16\,\text{mm}$ by $5$ to $8.5\,\text{mm}$) occurring in the pancreatic ducts of ruminants and humans, utilizing land snails and grasshoppers (Conocephalus maculatus) or tree crickets as intermediate hosts.

Heterophyes heterophyes

A minute intestinal fluke ($1$ to $1.7\,\text{mm}$ long) covered with scale-like spines that infects carnivores and humans following the ingestion of raw or salted brackish fish ('fessikh').

Metagonimus yokogawai

A minute intestinal fluke ($1$ to $2.5\,\text{mm}$ long) of carnivores, pigs, and humans whose ventral sucker is displaced to the right of the midline and fused with the genital sinus, acquired via raw freshwater fish.

Opisthorchis viverrini

A Southeast Asian liver fluke ($7$ to $12\,\text{mm}$ long) of carnivores and humans, acquired by consuming raw cyprinoid fish dishes (e.g., koi-pla) and strongly associated with cholangiocarcinoma (CCA).

Lawa Model

An integrated EcoHealth/One Health community program implemented in the Lawa Lake region of Thailand to control Opisthorchis viverrini through school programs, snail control, health education, and praziquantel therapy.

Clonorchis sinensis

The Chinese or Oriental liver fluke ($25\,\text{mm}$ by $5\,\text{mm}$) residing in bile ducts of mammals, distinguished by branched posterior testes, transmitted by raw cyprinid fish and causing periductal fibrosis and cholangiocarcinoma.

Nanophyetus salmincola

A small intestinal fluke of carnivores and humans transmitted by salmonid fish, notorious for transmitting Neorickettsia helminthoeca, the bacterial agent of 'salmon poisoning disease' in canids.

Salmon Poisoning Disease

A severe, highly fatal ($50$ to $90\%$ mortality) systemic disease of canids caused by Neorickettsia helminthoeca, which is transmitted during infection by Nanophyetus salmincola.

Fasciola hepatica

The common liver fluke ($30\,\text{mm}$ by $13\,\text{mm}$) characterized by broad shoulders, a distinct anterior cone, and branched internal organs, causing acute traumatic hepatitis and chronic hyperplastic cholangitis in ruminants.

Black Disease (Infectious Necrotic Hepatitis)

A fatal disease in sheep and cattle caused by Clostridium novyi Type B multiplying within anaerobic necrotic liver tracts created by migrating juvenile Fasciola hepatica.

Pipe-stem Liver

The gross postmortem appearance in chronic bovine or ovine fascioliasis where fibrotic and calcified bile duct walls form rigid, protruding white casts resembling the stems of clay pipes.

Bottle-jaw

Submandibular edema in ruminants resulting from hypoproteinemia and hypoalbuminemia associated with chronic liver fluke (Fasciola hepatica) infection.

Triclabendazole

The flukicide of choice for treating fasciolosis, highly effective against both early immature migratory flukes ($1$ to $5\text{ weeks}$ old) and adult Fasciola in bile ducts.

Fasciola gigantica

The giant liver fluke ($25$ to $75\,\text{mm}$ long by $12\,\text{mm}$ wide) found in Africa and Asia (including the Philippines), differing from F. hepatica by its larger size, less prominent shoulders, smaller anterior cone, and association with Lymnaea auricularia.

Fascioloides magna

The giant deer fluke ($23$ to $100\,\text{mm}$ long) without an anterior cone, naturally encapsulated in thin-walled fibrous cysts in cervids, but causing severe continuous tissue destruction or dead-end thick capsules with dark iron porphyrin in aberrant hosts.

Fasciolopsis buski

The giant intestinal fluke ($30$ to $75\,\text{mm}$ by $8$ to $20\,\text{mm}$) of humans and pigs in East and Southeast Asia, lacking shoulders, whose metacercariae encyst on aquatic plants such as water caltrop and water chestnut.

Parafasciolopsis fasciolaemorpha

A small fasciolid fluke ($3$ to $7.5\,\text{mm}$ long) inhabiting the gall-bladder and digestive tract of elk and goats in Poland and the former Soviet Union, transmitted by the swamp snail Planorbis corneus.

Family Echinostomatidae

A family of elongate intestinal flukes characterized by an anterior circumoral head-collar armed with a single or double collar of spines, tandem testes, and pretesticular ovaries.

Echinostoma revolutum

An intestinal fluke ($10$ to $20\,\text{mm}$ long) of aquatic birds and humans characterized by a circumoral head collar bearing $37$ spines, with $5$ corner spines located on each lateral angle.

Echinostoma ilocanum

A human intestinal fluke ($7\,\text{mm}$ by $1.5\,\text{mm}$) endemic to Southeast Asia (especially the Philippines) bearing an anterior collar armed with $49$ to $51$ spines, contracted by eating raw freshwater snails (Pila luzonica).

Paragonimus westermanii

The oriental lung fluke ($7.5$ to $16\,\text{mm}$ long) of carnivores, pigs, and humans, characterized by bifid tegumental spines, cystic encapsulation in lung parenchyma, and reddish-brown ('rusty') sputum containing operculated eggs.

Paramphistomum cervi

A conical, pear-shaped rumen fluke ($5$ to $13\,\text{mm}$ long) of ruminants; adults reside in the rumen and reticulum, while immature stages plug-feed on the duodenal mucosa, causing severe fetid diarrhea.

Plug-feeding

The destructive feeding behavior of immature Paramphistomum cervi, where mucosal tissue from the duodenum is drawn into the posterior sucker and pinched off, resulting in necrosis and hemorrhage.

Family Schistosomatidae

A family of dioecious, sexually dimorphic trematodes that inhabit the blood vessels of vertebrate hosts, lack an egg operculum, and infect hosts directly through skin penetration by cercariae.

Gynecophoric Canal

A ventral longitudinal groove formed by the folded lateral body margins of the male schistosome within which the longer, slender female resides during copulation.

Schistosoma japonicum

The Oriental blood fluke occurring in the mesenteric and portal veins of humans and animals (especially water buffaloes) in Asia, producing oval eggs ($70$ to $100\,\mu\text{m}$) with a small lateral knob, transmitted by Oncomelania snails.

Schistosoma haematobium

A human blood fluke of Africa and the Middle East that inhabits the venous plexus of the urinary bladder and pelvis, producing eggs ($144\,\mu\text{m}$ by $58\,\mu\text{m}$) with a sharp terminal spine passed in urine.

Schistosoma mansoni

A blood fluke of humans in Africa, the Middle East, and South America inhabiting the mesenteric venules of the bowel, producing elongated eggs ($114$ to $175\,\mu\text{m}$ by $45$ to $68\,\mu\text{m}$) with a prominent lateral spine.

Schistosoma nasale

A blood fluke inhabiting the nasal mucosa veins of ruminants and equines in the Indian subcontinent, producing boomerang-shaped eggs ($350$ to $380\,\mu\text{m}$) and causing 'snoring disease'.

Swimmer's Itch (Cercarial Dermatitis)

An itchy, maculopapular cutaneous hypersensitivity reaction caused by accidental penetration of human skin by the cercariae of non-human blood flukes (e.g., Trichobilharzia or Gigantobilharzia).

Schistosomula

The immature migrating stage of schistosomes formed when cercariae shed their forked tails and remodel their surface glycocalyx upon penetrating definitive host skin.

Gyrodactylus spp. — A small, viviparous monopisthocotylean lacking eye spots, reproducing by serial polyembryony (nested generations), with an opisthaptor armed with $1$ pair of central anchors and $16$ marginal hooklets.

Dactylogyrus spp. — An oviparous freshwater monopisthocotylean gill fluke of cyprinids characterized by $2$ pairs of cephalic eye spots and a posterior haptor bearing $1$ to $2$ pairs of anchors and $12$ to $14$ marginal hooklets.

Posthodiplostomum cuticula — A diplostomatid fluke with a distinctly two-segmented body; its encysted metacercariae induce host melanophore accumulation in the skin of cyprinid fish, causing black spot disease.

Alaria alata — An intestinal fluke of carnivores distinguished by two lateral ear-like tentacular processes on the anterior expanded forebody, utilizing an unencysted mesocercaria stage in frogs and paratenic hosts.

Eurytrema pancreaticum — A pancreatic duct fluke ($8$ to $16\,\text{mm}$ by $5$ to $8.5\,\text{mm}$) with an oral sucker larger than the ventral sucker, horizontal testes situated near the acetabulum, and a uterus filling the posterior body.

Clonorchis sinensis (Oriental or Chinese liver fluke) — A translucent biliary fluke characterized by deeply dendritic/branched posterior testes, a centrally looped uterus, and operculated eggs containing an asymmetrical miracidium.

Nanophyetus salmincola — A small, cream-colored intestinal fluke of carnivores with two large, oval testes situated ventrolaterally at the posterior ends of the ceca; biological vector of Neorickettsia helminthoeca.

Fascioloides magna (Giant deer fluke) — A large, thick, oval liver fluke ($23$ to $100\,\text{mm}$ long) with a rounded posterior margin, dark pigmentation, and lacking a distinct anterior cephalic cone.

Fasciolopsis buski (Giant intestinal fluke) — A large, thick-set distome ($30$ to $75\,\text{mm}$ by $8$ to $20\,\text{mm}$) of humans and swine that lacks cephalic shoulders, characterized by tandem branched testes and an unbranched intestine.

Echinostoma revolutum — An elongate intestinal fluke of birds and mammals featuring an anterior circumoral head collar armed with $37$ spines ($5$ corner spines on each ventral angle) and tandem lobed testes.

Paramphistomum cervi (Conical rumen fluke) — A conical, pear-shaped amphistome with a spineless cuticle and a large, fleshy posterior sucker (acetabulum) at its posterior tip, causing duodenitis through plug-feeding.

Schistosoma nasale egg — A distinctive large ($350$ to $380\,\mu\text{m}$ by $50$ to $80\,\mu\text{m}$), boomerang-shaped egg found in nasal discharges of ruminants and equines affected by snoring disease.