Unit 4 - Cestodes Flashcards
Acoelomates have:
NO body cavity
Describe the body shape of cestodes:
dorsoventrally flat chain of segments
Are cestodes monoecious or dioecious?
monoecious (hermaphroditic)
Where are the majority of cestode adults located?
SI
What life cycle stage of cestodes is typically not pathogenic?
adults
The body of the cestode is called a ______ and each of the segments are _________.
strobila; proglottids
Cestodes: direct or indirect life cycle?
indirect
How many intermediate hosts do “true” cestodes (Order Cyclophyllidea) have?
1
How many IH do “primitive” cestodes (Diphyllobothriidea) have?
2
What is the Cyclophyllidea scolex?
suckers +/- hooks
Diphyllobothriidea scolex?
Bothria (groove)
Genital pore location for Cyclophyllidea:
lateral
Diphyllobothriidea genital pore location:
medial (with the uterine pore)
How are Cyclophyllidea eggs shed?
in gravid proglottids; eggs without opercullum
How are Diphyllobothriidea eggs shed?
shed from pore in proglottids; eggs operculate
larval cestode in IH:
metacestode
Which stage of the cestode life cycle is more often associated with disease?
metacestodes
How many types of metacestodes do Cyclophyllideans have?
6 types (depends on species)
Metacestodes that develop into 1 adult in DH (only one worm is contracted):
- Cysticercus
- Strobilocercus
- Cysticercid
Metacestodes that develop into multiple adults in DH:
- Coenurus
- Unilocular hydatid cyst
- Alveolar (multiocular) hydatid
What are the two metacestode stages of Diphyllobothriideans? Which stage develops in 1st IH? 2nd IH?
Procercoid (1st IH), Plerocercoid (2nd IH)
Each plerocercoid develops into:
1 adult cestode
“bladder worm”
Cysticercus
Cysts in cysts; internal budding. Thick walled and slow growing:
Unilocular hydatid cyst (endogenous)
external budding:
alveolar (multiocular) hydatid (exogenous)
What are the two genera of importance from the Family Taeniidae?
Taenia, Echinococcus
What is the zoonotic potential of Taenia/Echinococcus?
humans may be DH or dead-end IH
DH and IH for Taenia, Echinococcus (Cyclophyllidea):
mammals (predator/prey)
DH for Taenia pisiformis:
canids
What is ingested by canids when dealing with Taenia pisiformis?
cysticercus
What is the IH for Taenia pisiformis?
rabbit
What is the DH for Taenia hydatigena?
canids
What is the IH for Taenia hydatigena?
ruminants, swine
Not as common as T. pisiformis in domestic dogs:
Taenia hydatigena
DH for Taenia taeniaeformis:
felids
IH for Taenia taeniaeformis:
rodents
larva ingested for DH infection with T. hydatigena:
cysticercus
What stage of T. taeniaeformis is ingested to cause infection in the DH?
strobilocercus
What is the general PPP for all Taenia spp.?
1.5 months
Pork tapeworm
Taenia solium
Beef tapeworm
Taenia saginata
Two Taenia spp. of public health importance:
solium, saginata
What is ingested from pork/beef meat to cause infection in humans (T. solium/saginata)?
cysticercus
Humans can be an accidental IH for which Taenia spp?
solium
Has very small adult stages but very large metacestodes:
Echinococcus spp.
Which stage of Echinococcus spp is zoonotic?
metacestodes
DH for Echinococcus granulosus:
canids
IH for Echinococcus granulosus:
primarily ungulates (humans)
What’s important to note about Echinococcus granulosus eggs?
Taeniid eggs: cannot differentiate from Taenia spp
Domestic cycle of Echinococcus granulosus:
dogs (DH) –> sheep (IH)
Sylvatic cycle of Echinococcus granulosus:
- wolf (DH) –> caribou (IH)
2. dingo (DH) –> kangaroo (IH)
How can humans become accidentally infected with E. granulosus?
primarily by ingesting eggs while handling dogs
DH for Echinococcus multilocularis:
foxes, other canids (rarely cats)
IH for Echinococcus multilocularis:
rodents (humans)
Pathology for this helminth mimics hepatic carcinoma when it accidentally infects humans:
E. multilocularis
E. granulosus larval type:
unilocular hydatid cyst
Larval type for E. multilocularis:
multilocular (alveolar) hydatid cyst
Location of E. granulosus in IH:
liver, lung, other
Location of E. multilocularis in IH:
abdominal cavity
PPP for Echinococcus spp?
~1 month
AKA 1. Cucumber tapeworm 2. Flea tapeworm and 3. Double-pored tapeworm:
Diplydium caninum
DH for Dipylidium caninum?
felids and canids
How does the DH get infected with D. caninum?
ingestion of infected IH
What is the IH for Dipylidium caninum?
Ctenocephalides felis
Zoonotic Dipylidium spp?
caninum
Dipylidium caninum eggs appear in:
“packets”
Infective stage for Dipylidium caninum:
cysticercoid
Location of adults in DH for Anoplocephala perfoliata?
ileum; cecum; ileocecal junction
DH for Anoplocephala perfoliata?
equids
IH for Anoplocephala perfoliata:
Oribatid mites (free-living mites)
May cause pathology in DH including inflammation and ulceration:
A. perfoliata
Which species of helminths have eggs with a “pyriform” appartus?
A. perfoliata, Moniezia spp.
DH for Moniezia spp?
ruminants
Common helminth of ruminants, not considered pathogenic:
Moniezia spp
IH for Moniezia spp?
oribatid mites
Infective stage of Moniezia spp:
cysticercoid
“fringed tapeworm”
thysanosoma spp
DH for Thysanosoma spp:
small ruminants; rarely cattle and deer
IH for Thysanosoma spp:
“book lice” or “bark lice”
infective stage for Thysanosoma spp:
cystocercoid
Has egg packets similar to Dipylidium:
Thysanosoma spp
Adults are in SI, bile ducts, and pancreatic ducts:
Thysanosoma spp
Spirometra DH:
felids, canids, raccoons
PH for Spirometra:
non-fish vertebrates (2nd IH)
1st IH for Spirometra:
copepod
Where is Spirometra spp common?
southeastern US
What GI signs are adult spirometra associated with?
vomiting, diarrhea, weight loss
When the plerocercoid causes disease:
sparganosis
DH for Diphyllobothrium latum:
canids, felids, humans
PH/2nd IH for Diphyllobothrium latum:
freshwater fish
1st IH for Diphyllobothrium latum:
copepod
Geographic distribution for D. latum:
cold climates (including northern US)
PPP for spirometra spp:
10-30 days
“holdfast organ”
scolex
Causes neurocysticercosis in humans:
Taenia solium
Also known as the “sparganum”
plerocercoid
What are the adult Diphyllobothriidean cestodes that are more likely to causes disease?
- Spirometra
- Diphyllobothridium
- Anoplocephala perfoliata
- Thysanosoma
Has dogs as the direct host with sheep as the intermediate host:
Taenia multiceps
Has dogs are the directs host with rabbits and cats as the IH:
Taenia serialis
What is the metacestode stage for both T. multiceps and T. serialis?
coenurus