Bailey & Scott's Diagnostic Microbiology: Intestinal Cestodes Flashcards

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Cestodes - Tapeworms

long, segmented ribbonlike body containing a scolex, strobila (neck region), proglottids (immature, mature (hermaohroditic), and gravid forms), and a smooth rostellum with hooks


Diphyllobothrium latum

freshwater broad fish tapeworm with crustacean as reservoir; scolex with two shallow grooves (bothria), unembryonated eggs operculated with terminal knob, and larvae (coracidium) ciliated with 6 terminal hooks


Diphyllobothrium latum laboratory diagnosis

fecal wet prep to identify eggs and proglottids; ova 58-75 by 40-50 um; proglottids rosette shaped uterus wider than long 3 by 11 mm; molecular for speciation, but sero not available


Diphyllobothrium latum clinical presentation

mostly asymptomatic; diarrhea, abdominal pain, vomiting; feeds on B12 causing pernicious anemia


Dipylidium caninum

cat or dog tapeworm; double pored with many proglottids with cucumber seed appearance which separate from worm to pass in stool; adult worms 10-70 cm long with scolex containing four suckers and armed rostellum


Dipylidium caninum lab diagnosis

identification of egg packets, proglottid and/or scolex in feces; sero tests available, NAAT not utilized


Hymenolepis nana

dwarf tapeworm with short armed rostellum scolex, eggs small with 4-8 polar filaments between eggshell oncosphere


Hymenolepis nana lab diagnosis

stool specimen analyzed for eggs since adult worms not found; mild eos, NAAT and sero to be developed


Hymenolepis diminuta

rat tapeworm (rats and mice), rare in humans, but acquire infection from contaminated grains; grain beetles breed in grain products and are easily ingested by humans; cysteroids remain viable as these foods are not heated prior to consumption; adult worm is 20-60 cm long


Hymenolepis diminuta lab diagnosis

wet mount and permanent stained smear to recover eggs in stool; proglottids disintegrate in gut; eggs are 80x70 um, round/oval with striated outer membrane and thin inner membrane with a smooth layer in between; six hooked oncospheres with no polar filaments


Taenia spp.

humans are definitive hosts; eggs are same in appearance in both species: saginata and solium; oncosphere contains six hooks and are radially-striated


Taenia saginata

cattle, beef tapeworm leading to Taeniasis caused by cattle ingesting contaminated eggs


Taenia solium

pigs and humans, pork tapeworm leading to Taeniasis and Cysticercosis caused by pigs ingesting contaminated eggs


Taenia saginata lab diagnosis

wet mount and permanent stained smear; eggs are indistinguishable from other species; differentiated by adult worms which are 4-12 m in length with unarmed rostellum of scolex; contains four large suckers but lacks the rostellum and is unarmed; proglottids 19x17 mm with 15-18 lateral branches and usually appear singly


Taenia solium lab diagnosis

wet mount and permanent stained smear; eggs are indistinguishable from other species; differentiated by adult worms which are 1.5-8 m in length with scolex with armed rostellum with 2 rows of large and small hooks; contains four large suckers and a rostellum containing two rows of large and small hooks which are armed; proglottids are 11x5 mm long and contain 7-13 lateral branches and chains of 5-6 segments


Taenia clinical presentation

mild abdominal symptoms, indigestion, diarrhea, and constipation, 15% eosinophilia, proglottid passage, more serious appendicitis, bile duct blockage due to migrating proglottids; major risks are taeniasis and cysticercosis



extraintestinal infection caused by Taenia solium when oncospheres invade intestinal wall, mature, and migrate to other tissues; found in brain and can lead to epilepsy and atypical lymphocytes in CSF, found on biopsy, CT, MRI; fecal eggs and proglottids are not diagnostic



cysticerci in the eye caused by Taenia solium which must be removed to prevent blindness