Cestodes: Cyclophyllidea & Pseudophyllidea Flashcards
What cyclophyllidean metacestode stage develops in an invertebrate IH? Give a species example.
cysticercoid (ex: hymenolepis nana)
What are the major morphological features of cyclophyllidea?
- acetabulate scolex 2. compact vitelline gland 3. apolysis
What 3 metacestode stages occur in vertebrate intermediate hosts?
- eggs eaten by vertebrate 2. cysticerus 3. ceonurus
Trace the path in the IH from egg to metacestode.
- adult worm in DH intestine 2. eggs passed in DH feces 3. eggs eaten by IH 4. develops into metacestode
Does a cysticerus have a scolex?
yes single scolex
Is the body of a cysticerus solid?
fluid filled sac
What is an example of a cysticerus?
Taenia solium & T. sasinata
In what genus does a hydatid development occur?
echinococcus
What are the two type of hydatid cysts? In which species does each occur?
- unilocular cyst in E. granulosis (endogenous budding) 2. multilocular (alveolar) cyst (exogenous budding) in E. multilocular
What is the common name of Taenia solium?
pork tapeworm
What are the intermediate & definitive hosts of Taenia solium?
IH = pig (ingests eggs) DH = human (ingests cysticerus)
What is the structure of the ovary & how many testes are found in the mature proglottid of Taenia solium?
trilobed ovary. 150-200 testes
How many lateral uterine branches are found in the gravid proglottid of Taenia solium?
7-13
What pathology is caused by Taenia solium?
often asymptomatic
What has happened to the human in cysticercosis?
human becomes IH by ingesting eggs & onchosphere penetrates intestine
What is the collagenous capsule?
capsule that forms around cysticerus as part of host immune response may be asymptomatic
What is a space occupying lesion?
pressure on host tissue. decreased circulation -> necrosis
In what parts of the body does disseminated cysticercosis occur?
viscera, muscle, subcuntaneous
What pathology can occurs in cases of ocular cysticercosis & neurocysticercosis?
blindness & adult onset epilepsy
What are the three most common mechanisms by which cysticercosis occurs?
- self-inflection (hand to mouth) 2. environmental contamination 3. internal autoinfection (reinfection by parasite w/o it leaving host)
How can infections with the adult Taenia solium worm & cysticercosis be diagnosed?
- MRI scans 2. surgery & ID
How are infections with the adult Taenia solium and cysticercosis treated? What are the mechanisms of action of the drugs?
surgery. mechanism of drugs = anti inflammatory
How can Taenia solium infection be controlled?
- sanitation 2. good hygiene 3. meat inspection 4. cook/freeze meat
How can meat be inspected for infection?
tongue of pig
How can meat be prepared to minimize the chance of infection?
cook over 65 degrees C or freeze at -10 degrees C for 14 days
What is the common name of Taenia saginata?
beef tapeworms
What are the intermediate & definitive hosts?
IH = cattle DH = humans
What does the egg of Taenia saginata look like?
identical to T. solium
Compare mature and gravid proglottids of Taenia saginata & T. solium.
mature: bilobed overy w/ 300-400 testes gravid: 15-20 lateral uterine branches
What are the symptoms generally associated w/ Taenia saginata infection?
most asymptomatic no cysticercosis
What is the treatment for Taenia saginata infection?
PZQ & niclosamide
How can Taenia saginata infection be controlled?
- sanitaiton 2. cook/freeze
Would you expect to find viable cysticerci in either rare, medium, or well done beef?
rare: 100% viable medium: 50-60% viable well: 0% viable
What is the definitive host for Echinococcus spp?
herbivores: sheep & cattle
How can humans get involved in the Echinococcus life cycle?
humans are never DHs but they can become IHs
Describe the scolex morphology and proglottids in Echinococcus species.
scolex: acetabulate & 3 proglottids
How does hydatidosis develop in a human?
human ingests eggs and becomes IH
What type of pathology can a hydatid cause?
- cycstic echinococcosis: space occupying lesion fluid leaks from cyst & into host tissue 2. alveolar echinococcocsis - cyst metastatic
What can happen if fluid leaks from the cyst?
host tissue is hypersensitized & can lead to anaphylaxis
Why is this important during surgical removal of the cyst?
not to nick the cyst
What is an osseous cyst?
space occupying lesion
What is the treatment for hydatidosis?
surgery or PAIR procedure (for inoperable cysts)
Describe the steps in the PAIR procedure.
- percutaneous Puncture of cyst 2. Aspiration of cyst fluid 3. replacement of cyst fluid w/ Injection of ethanol (kills germinal layer) 4. Reaspiration of ethanol 5. repeat 6. fill cyst w/ isotonic sodium chloride solution
What is the common name of Hymenolepis nana?
dwarf tapeworm
Does this Hymenolepis nana normally cause pathology in the human host?
very rare
Draw out life cycle of Hymenolepis nana.
answer questions in review packet
What is Diphyllobothrium latum’s common name?
broad fish tapeworm
What happens when the Diphyllobothrium latum egg hatches?
- anapolysis 2. operculum
What are the first and second intermediate hosts in Diphyllobothrium latum?
1st IH: coracidium in microcrustacean (copepod) 2nd IH: fish (goes into skeletal muscle but doesn’t undergo further development)
How does a definitive host become infected in Diphyllobothrium latum? What stage is infective to the DH?
eats 2nd IH (fish) not effective if fish is cooked. plercocercoid is infective stage
How long can a D. latum adult worm get?
up to 10m
What structures are found on the scolex of D.latum?
scolex: 2 bothria & proglotids
Where is the genital pore found on adult D.latum?
midventrally
Where does the uterine pore open on adult D.latum?
midventrally
What is the appearance of the uterus in a gravid proglottid on adult D.latum?
many loops “rosette”
Where in the world is infection with D. latum most common?
Scandinavia & US Great Lakes
What are some of the vague symptoms associated with D. latum infection?
?
What is the function of Intrinsic Factor?
binds to B12 and allows host to absorb B12 which is needed to synthesize Hb
What is pernicious anemia? How is this caused by D. latum?
bone marrow produces unsually large, abnormal, immature, RBCs (megaloblasts). tape worm secretes substances which block IF from binding to vit B12 which prevents Hb synthesis (worm absorbs B12)
How is D. latum infection diagnosed?
eggs in feces
How is D. latum infection treated?
PZQ, niclosamide, Vit B12
What genus causes sparganosis?
pseudophyllideaus
With which stage is the human infected with sparganosis?
larval
What are the three ways a person can become infected with sparganosis?
- drinks H2O that contains copepods infected w/ procercoid 2. ingest uncooked animal w/ plerocercoid (frog, snakes, birds) 3. physical contact w/ percocercoid (frog flesh or poultice)
