Cestodes (Flatworms) Flashcards
What is the phylum of cestodes and trematodes?
Platyhelminthes
Do Platyhelminthes have a body cavity?
no
2 subclasses of cestodes?
Eucestoda (true tapeworms)
Cotyloda (pseudotapeworms)
Is life cycle of tapeworm always direct or indirect?
indirect
How many intermediate hosts to tapeworms require?
one or two
What are the intermediate hosts of tapeworms?
arthropods
fish
mammals
Are domestic animals intermediate or definitive hosts of tapeworms?
intermediate
definitive, or
both
What are larval stages of domestic animal tapeworms called?
bladderworms
What path do bladderworms take after ingested by definitive host?
released from tissue of intermediate host and develop into adult tapeworms within digestive tract of definitive host.
What are the solid bodied cestodes?
procercoid
plerocercoid
tetrathyridium
How do domestic animals become infected with larval stages of tapeworms?
Ingestion of cestode egg or procercoid
Body of tapeworm?
long
dorsoventrally flattened
3 regions
scolex: head modified into attachment organ and
bears 2 to 4 muscular suckers (acetabula)
rostellum is snout, fixed or retractable, may
have hooks
strobila: the body composed of segments
(proglottids) in diff stages of maturity
proglottids near neck = immature, then
sexually mature proglottids, then gravid
segments that contain eggs
Which part of eucestodes breaks off its body and passes out of definitive host in feces?
gravid proglottids
How do cestodes get nutrients?
nutrients absorbed directly through body wall
Which organs occur in each individual proglottid of cestodes?
both male and female reproductive organs
How do cestodes reproduce?
cross-fertilization
self-fertilization
Cestode egg?
contains fully developed embryo (has six hooks in three pairs) = hexacanth embryo or oncosphere
Life cycle of cestode?
gravid proglottid shed fully intact in feces (singly or in chains)
they then rupture and release eggs
eggs ingested by intermediate host
develop into metacestode stage
metacestode (larval) stage may be in the form of a cysticercus, a coenurus cyst, a hydiatid cyst, or a tetrathyridium
definitive host becomes infected after ingestion of an intermediate host that contains metacestode stage
juvenile tapeworm then emerges from metacestode stage, attaches to lining of small intestine, and begins to produce strobili.
How do pseudotapeworms differ from true tapeworms?
reproductive organs and genital pores centrally located rather than laterally located.
What are bothria?
organs of attachment
pair of slitlike organs
located on lateral aspect of scolex
Eggs of pseudotapeworms?
operculated
released from uterus
passed in feces
contain coracidium (embryo)
Life cycle of pseudotapeworm?
released when egg contacts water
coracidium ingested by microscopic aquatic crustacean
develops into stage called a procercoid
crustacean ingested by fish or amphibian
develops into metacestode stage (i.e., plerocercoid or sparganum) within muscle of host
definitive host becomes infected after ingesting second intermediate host
What is the most common eucestode of dogs and cats?
Dipylidium caninum
How dogs and cats become infected with Dipylidium caninum?
ingestion of intermediate host flea
What do Dipylidium caninum proglottids contain?
thousands of unique egg packets containing 20 to 30 hexacanth embryos
Prepatent period of Dipylidium caninum?
14 to 21 days
What are the 3 canine taeniid tapeworms?
Taenia pisiformis
Taenia hydatigena
Taenia ovis
Where do canine taeniid tapeworms show up?
motile, terminal, gravid proglottids on feces, coat, or in bedding of host
How do dogs become infected with taeniid tapeworms?
ingestion of cysticercus-infected intermediate host
Intermediate hosts of Taenia pisiformis?
rabbits
hares
Eggs of taenid tapeworms?
slightly oval
43um to 53um by 43um to 49um (Taenia pisiformis)
36um to 39um by 31um to 35um (Taenia hydatigena)
19um to 31um by 24um to 26um (Taenia ovis)
contain oncosphere (hexacanth embryos) with 3 pairs of hooks
similar to Echinococcus species
What are the 2 Multicep species of tapeworms found in dogs?
Multiceps multiceps
Multiceps serialis
What is the hydatid cyst tapeworm of dogs?
Echinococcus granulosus
What is the hydatid cyst tapeworm of cats?
Echinococcus multilocularis
Why are the Echinococcus species important?
extreme zoonotic potential
Eggs of Echinococcus granulosus?
ovoid
32um to 36um by 25um to 30um
contains single oncosphere w 3 pairs of hooks
Eggs of Echinococcus multilocularis
ovoid
30um to 40um
Adult Echinococcus?
tiny (1.2um to 7.0um length) 3 proglottids (immature, mature, gravid) proglottids so tiny, often overlooked by client, vet tech, veterinarian when passed in feces
Diagnosis of Echinococcus infection?
identification of adult taken from host’s intestinal tract
antemortem diagnosis accompanied by purging the dog or cat with arecoline hydrobromide per os at 3.5 mg/kg and collecting the feces. (only when infection strongly suspected)
caution with handling because of zoonosis
Can humans be intermediate hosts to hydatid cysts of Echinococcus species?
Yes
They can develop in variety of organs in humans
What are the 3 equine tapeworms?
Anoplocephala perfoliata
Anoplocephala magna
Paranoplocephala mamillana
Where is Anoplocephala perfoliata found in horses?
small intestines
large intestines
cecum
Where is Anoplocephala magna found in horses?
small intestine
occasionally stomach
Where is Paranoplocephala mamillana found in horses?
small intestine
occasionally stomach
Eggs of Anoplocephala perfoliata?
thick walls
one or more flattened sides
65um to 80um diameter
Eggs of Anoplocephala magna?
slightly smaller than perfoliata
thick walls
50 to 60um
