L24 (Worm Parasites) - B Flashcards
Four features of Cestodes (Tapeworms)???
- Monoecious (unisex)
- No digestive system
- Transmission by ingestion of ova
- Cause little or no harm – unless present in large numbers
What are three examples of tapeworms?
T. saginata
T. solium
D. latum
Which organism has the following features?
- Diecious
- Complete digestive system
- Wide variation in mode of transmission
A. Nematodes (Roundworms)
B. Cestodes (Tapeworms)
A. Nematodes (Roundworms)
Which three nematodes (roundworms) directly penetrate the skin with their infectious larvae?
- S. stercoralis
- N. americanus
- A. duodenale
Which three nematodes (roundworms) ingest contaminated soil?
- E. vermicularis
- T. trichiuria
- A. lumbricoides
Match the Cestode term to the definition…
____: Structure on anterior end of worm with suckers (+/- hooks) that functions to attach the worm to the intestinal cell wall
_____: Body of tapeworm; composed of many segments called proglottids
_____: Segments, each of which contains a complete set of sex organs (both M/F); can break off and pass out of body into stool
A. Scolex
B. Strobila
C. Proglottids
A. Scolex: Hooks on anterior end
B. Strobila: Tapeworm body
C. Proglottids: Segments that contain sex organs
_____: Mature, egg filled proglottids, located at posterior end of organism
____: Cysts formed by larvae embedded in body tissues
A. Cysticerci
B. Gravid Proglottids
B. Gravid Proglottids: Mature, egg filled proglottids, located at posterior end of organism
A. Cysticerci: Cysts formed by larvae embedded in body tissues
Which part of Cestodes are important for attachment? reproduction?
Attachment - Scolex
Reproduction - Proglottids
What three features of Cestodes can you used to differentiate them?
- Eggs
- Scolex
- Proglottids
True or False: The eggs of e. saginata and T. solium are indistinguishable from one another
True
- Both have radial striations on shell
Which of the following has four suckers and NO hooks?
A. T. solium scolex
B. T. saginata scolex
B. T. saginata scolex
Which of the following has four suckers and is “armed” with hooks (rostellum)?
A. T. solium scolex
B. T. saginata scolex
A. T. solium scolex
How do the gravid proglottids of T. saginata compare to those of T. solium?
T. saginata
- 12 to 20 uterine branches
T. solium
- 5 to 10 uterine branches
Describe the D. latum ova and gravid proglottid:
Ova
- operculum
- polar knob on opposite ends of egg
Gravid Proglottid
- rosette shaped uterine branches
Which of the following scolex has two grooved suckers, one on each side of the scolex?
A. T. saginata
B. T. solium
C. D. latum
C. D. latum
____ is the definitive host of T. saginata while ____ is the intermediate host of T. saginata
Human = definitive host
Cow = intermediate host
In T. saginata, cow will ingest embryonated eggs. Larvae migrate to tissues to become ____
cysticerci
How can humans become infected with T. saginata?
Ingestion of raw or undercooked beef
- Upon consumption, stomach acids release of cysticerci from muscle tissue
- Scolex attaches to intestinal wall + growth
- Proglottids passed in feces
Life cycle of T. solium is similar to T. saginata, except in the case of T. solium ___ (intermediate host) eats embryonated eggs
Pig - intermediate host
Human - definitive host
What structure can you identify in feces to diagnose T. solium or T. saginata?
Proglottids
In D. latum, larvae hatch in the water and ___ eats them. Following this, minnow eat infected ____. Larger fish eats infected minnow.
copepod (small crustacean)
True or False: Pleurocercoid larva are ingested with infected raw fish in D. lactum
True
When D. latum infection occurs, scolex of____ attaches to mucosa.
Where does gravid proglottid break up?
pleurocercoid
colon
True or False: With D. latum infection, usually you will see eggs in feces (not intact proglottid)
True
Where are D. latum eggs deposited (where they will eventually hatch)?
Water
Definitive vs. Intermediate host of D. latum?
Human - definitive host
Fish - intermediate host
True or False: In D. latum infection, pleurocercoid larva is ingested with infected raw fish
True
Cysticercosis is an invasive human disease in humans, which can produce cysticerci in brain, eye, and muscles.
One can only develop this infection, however, if they ingest embryonated ____ eggs – in this case: human is intermediate (dead end) host
A. T. solium
B. D. latum
C. T. saginata
A. T. solium
Compare and contrast disease manifestation (Cysticercosis vs. Taeniasis) in T. solium:
What are the main signs and symptoms associated with Cestodes (tapeworms)?
- Usually no symptoms!
1) Cysticercosis
- Occulocysticercosis: blindness
- Neurocysticercosis: seizures
2) D. latum can cause pernicious-like anemia
What are two ways to diagnose Cestodes (tapeworms)?
1) Mature worms in intestine
2) Proglottid or ova (D. latum) in fecal sample
How do you r/o Cysticercosis?
1) CT/MRI - calcified lesions in brain, SC, or skeletal m
2) Serological (EIA) to worm antigens
How do you prevent Cysticercosis?
1) Proper disposal of human feces
2) Routine meat inspection
3) Good personal hygiene
What type of infections can be caused by Enterobius vermicularis (pinworm)?
A. Non-diarrheal, invasive
B. Non-diarrheal, non-invasive
C. Diarrheal, invasive
D. Diarrheal, non-invasive
B. Non-diarrheal, non-invasive
- Note: most common intestinal nematode in the US
True or False: Enterbiasis is a dioecious nematode (roundworm)
True
Compare and contrast adult male vs. adult female Enterbius vermicularis adult worms:
Enterobius vermicularis
Adult male
- Curved, relatively blunt posterior end
Adult female
- Long, pointed tail
Which parasite is inhaled/enters body via finger to mouth, leading to egg ingestion and larvae hatching in the small intestine, eventually migrating to the colon?
Pinworm (enterobiasis)
True or False: Adult female pinworms migrate at night to perineum and lay eggs around anus, creating itching sensation
True
What is the difference between autoinfection and retroinfection, as in the case of Enterobiasis (pinworms)?
Retroinfection: migration of newly hatched larvae from anal skin back into the rectum
Autoinfection: common form of transmission, by which infection occurs via egg ingestion due to contaminated hands, foods, toys
How is enterobiasis transmitted?
Fecal oral route
True or False: One can dx enterobiasis by looking at child’s stool or urine sample
False - you can rarely see pinworm eggs via stool or urine samples
Which type of infections can arise due to T. trichiuria (whipworm)?
Non-diarrheal minimally invasive parasitic infestations
True or False: Whipworm larvae hatch in small intestine, then migrate to the colon. Mature in colon. Unembryonated eggs pass in feces, while those that are embryonate enter into the soil.
True
Ingestion of embryonated eggs from soli leads to infection of ____
Trichuriasis
What are the four soil-transmitted helminths?
1- Trichursis
2 - Ascaris
3 - Hookworm
4 - Strongyloides
Prolapse rectum and dysentery are a side of infection by which parasite?
Trichuriasis (whipworm)
How do you dx Trichuriasis?
Find ova in stool
Three features of Trichuriasis?
- shape?
- color?
- stain?
- Barrel shaped
- Yellow-Brown
- Bipolar unstained prominences
How do you avoid getting sick with Trichuriasis?
Wash, peel, or cook raw veggies from the soil
Which four parasites can cause non-diarrheal, invasive, parasitic infections?
- A. lumbricoides (giant worm)
- A. duodenale (hook)
- N. americanus (hook)
- Strongyloides stercoralis (thread)
You are looking at an ova that has been identified as belonging to A. lumbricoides (giant worm). It is thick, transparent, and coarsely mammillated shell, typically golden-brown in color. Is it?
A. Fertilized
B. Unfertilized
A. Fertilized
Describe lifecycle of A. lumbricoides:
Describe lifecycle of A. lumbricoides:
Signs and symptoms of A. lumbricoides?
1) Cough, sputum w/larvae + eosinophils
2) Pneumonitis
Dx Ascariasis?
See ova microscopically in feces – prevent same way as Trichuriasis
Necator americanus and Ancylostoma duodenale are ____, species that are intestinal parasites in human
hookworms
What are the 3 stages of hookworm larvae?
1 - Embryonated
2 - Rhabditiform larva
3 - Filariform larva*
True or False: The filariform larva stage is the infectious stage of hookworm
True
True or False: On contact with human host, larvae of Hook worm penetrate skin and are carried through b. vessels to heart, then lungs
True
How do hookworms cause blood loss in their host?
As adults, hookworms live in lumen of small intestine, where they attach to intestinal wall, results in blood loss for host
Hook worm lifecycle?
True or False: Hookworms can be acquired by walking barefoot
True
Dx hookworms?
Sx of hookworms?
Prevention?
Thin-shelled eggs
Sx: anemia + protein deficiency
Prevention: wear shoes
Humans are accidental hosts of zoonotic hookworms, can develop ___ ___ ___ (CLM)
cutaneous larva migrans
True or False: Strongyloides stercoralis has a similar morphology to hookworm, but it less prevalent
True
What is the infectious, third stage larvae of S. stercoralis larvae?
Filariform larvae
Which larvae is used for diagnosis (diagnostic stage) of S. stercoralis?
A. Filariform larvae
B. Rhabditiform larvae
B. Rhabditiform larvae
Which parasite is the only one that is known to have a free-living cycle that takes place in the soil?
Strongyloides
Strongyloides life cycle?
True or False: Strongyloides can do internal (intestinal) or external (perianal) autoinfection
True
True or False: The rhabditiform larvae can either be passed in stool or cause autoinfection
True
Where do the eggs of Strongyloides hatch into larvae?
A. Intestine
B. Colon
C. Liver
A. Intestine
What are 2 features of Strongyloides life cycle that makes them more complex than other nematodes?
- Alternates between free living and parasitic life cycles
- Potential for auto-infection and multiplication within host
How do you dx Strongyloidiasis?
Larvae (NOT EGGS!) in stool
- No sx
