non-diarrheal non-invasive parasitic infestations: flatworms/cestodes Flashcards
tapeworm spp.
Taenia saginata, T. solium
Diphyllobothrium datum
Hymenolepis nana
tapeworms are ??
long, segmented worms: head- scolex neck segmented body: proglottids entire "tape: strobila *monoecious, of Cestoda class*
Cestoda class
Tenia, Diphyllobothrium, Hymenolepis, Dipylidium, Echinococcus, Spirometra
tapeworm larvae attach via the ?? in the ?? and dev. into adult worms
require 1 or more ??
scolex (head)
small intestine
intermediate hosts
tapeworm infection typ. transmitted how??
how so??
fecal-oral or ingestion of contaminated, undercooked meat
eggs pooped from host–>into environ.–>eaten by interned. host–>hatch and larvae enter host tissue and encyst–>then primary host eats the intermediate host meat and gets the cyst
humans are the primary host for ??
thus ??? necessary to sustain life cycle
Taenia, Diphyllobothrium, Hymenolepis, Spirometra
human fecal contamination of the environment
?? only cestodes for which humans can function as both primary and intermediate host,
therefore ??? is possible
Hymenolepis spp. and Taenia solium
autoinoculation
in ??? cestode spp, humans function as intermediate hosts
?? exist within tissue and migrate thru diff organ systems
Echinococcus spp., Spirometra spp., Taenia multiceps
larvae
Taenia solium hosts
primary: humans (stays in gut)
intermediate: pigs, humans*, dogs, cats, sheep (can go anywhere)
Taenia saginata hosts
primary: humans
intermediate: cattle
Diphyllobothrium hosts
primary: humans
intermediate: fish
Hymenolepis hosts
primary: humans
intermediate: H. nana has none (autoinoculation: fecal-oral)
H. diminuta- rodents
D. caninum hosts
primary: humans, dogs, cats
intermediate: fleas on dogs/cats
Echinococcus hosts
primary: dogs
intermediate: humans, sheep, cattle, goats, horses, camel
Spirometra hosts
primary: humans
- I believe humans function as intermediate host as well
Taenia multiceps hosts
primary: humans?
intermediate: hares, rabbits, squirrels, humans (rarely)
many cestode infestations are ?? and depend on ??
asymptomatic, worm burden
beef tapeworm ??
pork tapeworm ??
acquired how?
T. saginata
T. solium
ingestion of cysticerci larvae in improperly cooked meat
T. sag and T. sol larvae are released when ?? and attaches to ?? via ??
adult worm may be how long ??
during digestion, attaches sm. intestine via the scolex
may be 5-8 meters! T. sag>T. sol
as Taenia proglottids filled with eggs grows, they break off and migrate thru the ??
large intestine, rectum, anus–>exterior
T. saginata may be pooped out or exit by themselves
the cycle continues if…
?? are released during digestion and hatch into ?? in the sm. intestine then ??
proglottid is eaten by animals
eggs, larvae
then actively penetrate sm. intestine of pig/cow and migrate via blood to all organs, may be eaten by humans
cysticercosis happens when humans eat ??? of what cestode??
therefore transmission via ??
the ?? then penetrate the intestinal wall (like in intermed. host) and encyst in host tissue such as ??
ova of T. solum rather than larval form
fecal contam. of food, water and poor personal hygiene (auto infection) -NOT eating meat
larvae
CNS, muscle, eye
*much more serious than tapeworm infestation!
D. latum (fish tapeworm) cycle
eggs must ??
fish ingests ?? and the ?? penetrates the sm. intestine and lives in muscle and develops into ??
enter fresh water for cycle to continue–>intermediate stages
infected water flea, perocercoid larva pleurocercoid larva (infective stage for humans)
Diphyllobothrium latum infects humans when ??
D. latum absorbs ??? in human host and big one can cause ??
eating raw/undercooked fish with larva
cycle starts over
Vitamin B12–>megaloblastic anemia
Hymenolepis nana (Dwarf tape worm) are ?? when pooped out
immediately infective
can’t survive more than 10 days in external environment
H. nana eggs are eaten by ?? and develop into ?? which can ?? and develop into ?? in the small intestine
an arthropod(beetle, flea) intermediate host? cysticercoids, can infect humans/rodents when eaten and dev. into adults in sm. intestine
H. nana var. fraterna
infects rodents, arthropods as intermediate hosts
H. nana eggs ingested via ??
and release their ?? which ?? and dev. into ??
contaminated food or water or feces-contam. hands
oncospears (hexacanth larvae) –> penetrate the intestinal villus and develop into cysticercoid larvae
when the ?? rupture , the H. nana cystercercoids go back to the ?? and do what ??
villus
intestinal lumen, evaginate their scoleces, attach to intestinal mucosa and dev. into adults that live in the ileal portion of the sm. intestine producing gravid proglottis
H. nana ?? are pooped out when release from proglottids through its ?? or when proglottids ?? in the sm. intestine
eggs
genital atrium
disintegrate
alternatively, H. nana eggs release their ?? which penetrates the villus, continuing the ?? without passage through external environment
name of this cycle? which allows the infection to ??
hexacanth embryo
infective cycle
internal autoinfection, persists for years (vs 4-6 wks)
Canid Echinococcus spp
E. granulosus causes a ?? produces eggs that are passed with ??
typical tapeworm inf.
dog poop
in the intermediate host, E. granulosus eggs hatch into ?? that travel through blood and form ?? in host tissue
what organs?
how big??
oncosphere larvae
hydatid cysts
liver, brain, lungs, NOT subcutaneous tissue
size of a softball or basketball! and may contain sev. smaller “balloons” w. in main cyst
make inf. animals easier prey (i.e. moose)
T. saginata risks/regions
beef
Central Asia, near East, Central and East Africa
alternative intermediate hosts (i.e. exotic animals besides cattle: llamas, giraffes, buffalo, etc.)
T. solium risks/regions
pork
Mexico, Central and South America
also Southern Europe, Africa, SE Asia, India, Phillipines
-like everywhere
D. latum risks/regions
fish
N. America, Siberia, Europe, Scandinavia, Baltics, Japan, Chile
alternative definitive hosts (besides humans): seals, cats, bears, minks, foxes, wolves, etc.)
?? is the most commonly dx tapeworm inf. in the US
affects who most commonly??
transmitted how??
H. nana
school-aged, institutionalized kiddos in SE US (day care)
children in dry, warm regions of developing countries
fecal-oral, person-person may occur: think mt. range; it propagates
Hymenlepis diminuta, mostly a cestode of ??
humans are (rarely) infected by ingesting mealworms/grain beetles that contain ??
in what foods??
rodents
cysticercoid larvae
dried grains, cereals, flour and dried fruit
Eichinococcus spp. are cestodes that inhabit ??
?? are intermediate host
?? are at high risk
the small bowel of canids (dogs, wolves, foxes)
humans
sheepherders
tapeworm inf. are typically ??
otherwise presentation:
asymptomatic
vague: GI discomfort, weakness, dizziness, salt craving, diarrhea
uncontrollable screaming (i.e. find proglottids of T. saginata in poop or on own)
T. solium
symps assoc. with ?? depend on ??
most sev. if in ??
cysticercosis, worm burden and location
eye (blindness) or brain (neurocysticercosis: seizures-70%)
where is neurocysticercosis prevalent??
Mexico, Central and South America
immigrant pop
D. latum presentation
if large worm/several worms–>
pernicious-like anemia (vit B12 def)
if Echinococcus (canine tape worm) cysts rupture, may cause ??
most serious complication that has a 90% fatality rate @ 10 yrs??
?? can happen in response to worm Ag suddenly release into circulation with cyst rupture
fever, pruritus, urticaria, eosinophilia, anaphylaxis
untx symptomatic liver involvement
erosion of surrounding tissue, systemic anaphylaxis (type 1 hypersensitive)–>mediated by elevated eosinophils and IgE
dx cestodes (tapeworm) infection via finding
adult orgs in intestine, ova/proglottid in fecal sample
dx cysticercosis imaging
CT and MRI may show calcified lesions in subarachnoid or intraventricular spaces
-but almost any brain/SC region could be affected
skeletal muscle encystment
dx cysticercosis labs
blood: detect Abs to worm Ags- ELISA (definitive)
or dx if larvae are surgically removed
intestinal tapeworm tx
Niclosamide: uncouples oxidative phos. in tapeworm
or
Praziquantel: interferes with adenosine uptake
cysticercosis tx
Albendazole
(no anticonv. or dexameth interactions- given for CNS complaints)
use corticosteroids (dexamethasone) to reduce inflammation during tx
sx may be required
Echinococcus dx
imaging (US, MRI, CT)
serology to comfirm (ELISA, Western blot)
issues with cyst removal in Echinococcus tx
accidental rupture–>anaphylaxis
accidental spread of larvae–>daughter cysts
secondary bac infection
Echinococcus tx
sx: aspiration and instillation of cysticidal agents and removal of cyst
albendazole, mebendazole
response depends on cyst size and location
T. saginata ppx
cook beef, prev. human fecal contam of pastures
prolong deep freezing to kill cysticerci
T. solium ppx
rare in US, typ. from Latin America, Asia
personal hygiene important for cysticercosis (self-inf or person-person)
mass tx w. praziquantel/niclosamide in endemic areas
D. latum ppx
cook fish throughly
Echinococcus ppx
de-worm/tx dogs
wash hands throughly
avoid unwashed/raw veggies where canines poop
FLUKES (non-cestode): intestinal trematodes
infected how ??
what region ??
flat, hermaphroditic worms, few mm-cm
>40-50 mil ppl ww
food-borne
SE Asia
most common Flukes/trematodes spp
Fasciolopsis buski
Heterophyes heterophys
Metagonimus yokogawai
Echinostoma spp.
Fluke infection presents like ??
a malabsorptive illness
eat environmentally incubated cysts (water chestnuts)
can’t put on muscle mass
