Bailey & Scott's Diagnostic Microbiology: Tissue Cestodes Flashcards

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tissue cestodes

eggs are accidentally acquired; larvae migrate throughout the body and deposit in organs and tissues; adult stage not reached in human host


Taenia solium tissue complications

lead to cysticercosis from larval infection, rare in US, oncospheres invade intestinal wall; most severe infection is neurocysticercosis, cysticerci in the eye; diagnosed by eggs and proglottids found by tissue biopsy, CT, and MRI



caused by two main species are granulosus and multilocularis; detected by biopsy, CT, MRI, and differentiated by pathology; adult worms present in animal intestine, eggs and proglottids passed in stool, ingested by humans, hatch in duodenum and enter bloodstream where they reach organs (especially liver) and develop fluid-filled cysts; the inner lining of outer membrane buds off small mini-cysts inside, brood capsules are miniature replicas fo main hydatid cyst, and float freely within main cyst or remain attached by thin connective strand; forming miniature larval tapeworms within themselves


Echinococcus spp.

smallest of all tapeworms: 3-9 mm long; body is scolex with three proglottids; terminal proglottid is gravid and longer than wide, scolex has four suckers and rostellum with 25-50 hooks; eggs not found in stool so not diagnostic, but measure 30-35 um in diameter, radially-striated, oncosphere contains 6 hooks


Echinococcus hydatid cyst

large, expanding, fluid-filled structure with thin, almost see-through, outer wall


Echinococcus granulosus lab diagnosis

slow growing abdominal tumor with or without Eos, cysts are identified in organ; sero tests detect and MRI or CT yields fluid-filled cysts


Echinococcus multilocularis

second most common cause of human echinococcosis; fox tapeworm; foxes and cyotes are most common definitive host, rodents are intermediate


Echinococcus multilocularis clinical presentation

cause alveolar hydatid disease (fatal); cyst lacks laminated membrane and develops connected chambers with little fluid; cysts form in liver and metastasize to lungs or brain and are found by CT or MRI