Bailey & Scott's Diagnostic Microbiology: Intestinal Trematodes Flashcards


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1

trematodes

leaf-life, unsegmented appearance, dorsoventrically flattened with oral suckers at anterior end a ventral sucker; hermaphroditic and digenetic (can replicate through sexual and asexual cycles); includes egg, larval, and adult cycles; human is definitive host, snail or mollusk are larval intermediate host, fish, crab, other snails as 2nd intermediate host to encyst; reside in small intestine and eggs are shed in feces; also known as flukes; ingestion of metacercariae

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Fasciolopsis buski

common in Asia and Indian subcontinent and areas where humans raise pigs and consume freshwater plants; giant intestinal fluke; humans and hog are definitive host, snails and water vegetation are intermediate; fish-eating animals are reservoir host

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Fasciolopsis buski clinical presentation

most infections are light and asymptomatic; in light infections flukes are found in the duodenum and jejunum; in heavy infections they are found in the stomach and intestinal tract, attaching and causing inflammation, hypersecretion of mucous, hemorrhage, ulceration, and abscess formation, bowel obstruction, eos, abdominal pain, diarrhea, malabsorption, and ulceration

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Fasciolopsis buski adult

elongate/ovoid with no cephalic cone structures measureing 20-75 mm long; poorly-developed oral and ventral suckers; reside in intestine of mammalian host

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Fasciolopsis buski eggs

broadly ellipsoid operculated, yellow brown measuring 140-80 um; umembryonated when passed in feces

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Heterophyes heterophyes

found in Egypt, the Middle East, and Far East, it is the smallest trematode to infect humans caused by ingestion of pickled or uncooked fish

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Heterophyes heterophyes clinical presentation

presents with mild inflammatory reaction-diarrhea and colicky abdominal pain; in heavy infections presents with mild symptoms, along with ulceration of intestinal walls; worms burrow deep in intestinal walls releasing eggs into circulation; lesions occur in heart and brain

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Heterophyes heterophyes adults

minute intestinal fluke measuring only 1-2 mm; testes large and paired, situated near small ovary; surface covered with tiny spines; reside in small intestine

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Heterophyes heterophyes eggs

tiny, only 15-30 um operculated with shoulders, yellow brown; formalin-ethyl acetate sedimentation recommended for recovery

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Metagonimus yokogawai

most common fluke in Far East transmitted by ingesting contaminated raw or undercooked fish

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Metagonimus yokogawai clinical presentation

dependent on worm burden; eggs infiltrate intestinal capillaries and lymphatics, then carried to myocardium, brain, spinal cord, and other tissue; emboli or granulomatous reactions

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Metagonimus yokogawai adults

Minute-measuring 1-2.5 mm long; distinctive feature is position of ventral sucker aside midline; reside in small intestine of definitive host

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Metagonimus yokogawai eggs

tiny measuring 26-30 um long by 15-17 um wide; operculated with shoulders, yellow brown; formali-ethyl acetate sedimentation recommended for recovery