Cestodes Flashcards
cestodes: general characteristics
- all are parasitic: adults in sm. intestine of vertebrates, larvae in invertebrates or vertebrates
- no digestive, circulatory, respiratory or skeletal systems
- muscular system & nervous system
- body of scolex (mouth) & proglottids (body segment)
- hermaphroditic
cestodes - taxonomy
cestodes aka tapeworms are a class of platyhelminthes aka flatworms
proglottid types
immature proglottids - anterior end
mature proglottid - middle of body
gravid proglottid - toward posterior, full of eggs,
species specific in both IH and DH
two orders within cestodes
- cyclophyllideans = true tapeworms
2. pseudophyllidea = pseudotapeworms
general characterisitcs of cyclophyllideans (true tapeworms)
- has a scolex of 4 different suckers (can be armed or unarmed)
- proglottids (NO uterine pore)
- each egg can form one tapeworm
- IH must ingest eggs
- metacestode - larvae DH must ingest
cysticercoid
- single scolex NOT invaginated
- usually seen in invertebrate IH like fleas or mites
- this is a TYPE of metacestode
cysticercus
single invaginated scolex usually vertebrate IH
- inside out, small fluid-filled bladder
- a TYPE of metacestode
coenurus
a large fluid-filled bladder containing multipe invaginated soclices in vertebrate IH
goal of the cyclophillidean
KILL the IH because it cannot complete its life cycle until its eaten by the DH
unilocular hydatid cyst
broad capsules with 100s - 1000s of protoscolices, very large, thick-walled filled with fluid
multilocular hydatid cyst
not contained by the thick-walled compartment
characteristics of Pseudophyllideans
scolex: bothria = 2 slit-like structures (no hooks or suckers)
proglottids - 1 set of repro organs, central genital pore
- uterine pore in center
- eggs are operculated and WILL float in fecals!
- larvae have a metacestode in IH
diagnosis of cestodes (tapeworms)
fecal floatation
simple vs. centrifugal fecal flotation
flotation is how you find most nematod eggs, larva and tapeworm eggs.
- need at least 1 gm
- use correct soln
- for simple, it must SIT for 15-20min
Dipylidium caninum : taxonomy
part of order cyclophyllidean class cestodes phylum platyhelminthes
dipylidium caninum: general characterisitics
aka cucumber seed tapeworm
- SI of dogs, cats, children
- found worldwide
- indirect lifecycle
- IH: fleas, dog louse
- metacestod: cysticercoid
- adults repro system has: 2 sets of proglottids, NO uterine pores.
adults scolex has 4 suckers, armed with rostellum & hooks
- eggs: found in packets, hexacanth embryo
life cycle of dipylidium caninum
- adults in SI of cat or dog. gravid proglottids break away from the chain and are passed in feces
- proglottids rupture - egg packets released as well as individual eggs
- eggs are ingested by IH - larval fleas or louse
- hexacanth embryo matures to cysticercoid once adult flea is on DH needs 30 - 32C
- reaches infective cysticercoid within 36 hours after flea is on DH
- flea is ingested by DH - cysticercoid digested out, releases, scolex, attaches to SI - begins to grow.
- prepatent period = 2-3 weeks
dipylidium caninum : pathogenicity
- usually not pathogenic
- heavier infections cause: constipation, diarrhea, pot-bellied appearance
- migrating proglottids may make host itch
- steals nutrition from DH
control of dipylidium caninum
control fleas &/or lice
Anoplocephala spp. taxonomy
species of order cyclophyllidean, class cestode, phylum platyhelminthes
Anoplacephala perfoliata
“lappeted tapeworm”
- congregates near ileocecal valve
- has lappets behind each sucker <– diagnostic feature
anoplocephala magna
“large scolex tapeworm”
- no lappets
- SI, especially jejunum
- large scolex which does NOT have hooks
paranoplacephala mamilana
“dwarf tapeworm”
- SI
- narrow scolex
- NO lappets
- has 4 suckers
life cycle of anoplacephala spp.
- DH is horse
- prepatent period = 6-16 weeks
- eggs short-lived, must be ingested quickly
- egg hatches and cysticercoid develops over 8-20 weeks
- infection accidental during grazing
pathogenicity of anoplacephala spp.
anoplacephala perfoliata: attaches to GI mucosa, causes ulcerative lesions and mucosal degeneration, possible risk factor for impaction colic, chronic symptoms: ill thrift, recurring diarrhea, weight loss
anoplocephala magna & paranoplacephala mamilana: rarely disease, large numbers may cause hemorhagic enteritis
diagnosis of anoplacephala spp.
- fecal flotations - look for proglottids
- following to find species:
- indirect ELISA
- serologic ELISA
- necropsy
Taeniids: taxonomy
order cyclophllidean, class cestode, phlyum platyhelminthes
taeniids: general characterisitcs
- large worms
- proglottids longer than wide
- ARMED (row of hooks)
- single genital pore
- all eggs look exactly alike, 6 exocant hook embryo inside egg
- humans can be IH host
- all have metacestode stages (in IH)
- all dx via fecal flotation
life cycle of general taeniid
- adult tapeworms attach to SI of DH. gravid proglottids passed in feces, rupture, eggs released
- IH ingests eggs - hatch in intestine. oncosphere (hexacanth embryo) released, penetrates intestinal mucosa, enters circulation
- metacestode stage develops in various organs or tissues
- DH infected by ingestion of raw, undercooked meat. metacestode releases scolex which attach to SI - grows to adults
taneia pisformis (csticercus pisiformis)
“abodminal tapeworm” “abdominal bladderworm” “rabbit tapeworm”
adult: SI of dogs, 200cm
metacestode: peritoneal cavity of rabbits & hares, frequently attach to serosal surfaces of abdominal organs
spirometra mansonoides
order pseudophyllidean, class cestode, phylum platyhelminthes
spirometra mansonoides: general characteristics
hosts: felids and canids
- common tapeworm of cats in Fl - they are everywhere here
zoonotic! humans will get larval stages but not the adult
- uterus is in the center, very dark spot straight down middle making it easy to ID
- distribution: mainly southeastern US
- repro system: one set/proglottid –> uterine pore
- scolex with 2 bothria
- eggs: operculate
- metacestode stages: procercoid (1st IH usually copepod), plerocercoid (2nd IH, usually frog, rat, snake)
life cycle of spirometra mansonoides
- adults in SI of the cat or dog. eggs are passed in feces via uterine pore
- a coracidium develops in egg and emerges upon contact with water
- 1st IH - copepod ingests coracidium - develops into procercoid
- 2nd IH - frog, rat, snake, ingests copepod - procercoid develops into plerocercoid
- plerocercoid encysts in muscles of 2nd IH
- 2nd IH/plerocercoid ingested by DH - digested out of muscle, attaches to SI - grows and matures
pathogenicity of spirometra mansonoides
- most cases asymptomatic may have vomiting, diarrhea, weight loss
- zoonosis either by ingestion of copepod (ie frog legs) or via 2nd IH by applying cold meat as compress to an open wound
diagnosis of spirometra mansonoides
one of the hardest tapeworms to treat
- fecal examination: should look bubbly
control of spirometra mansonoides
- preventing predation of 2nd IH by dogs and cats
- avoid ingesting undercooked meat
