Deck 54: Intestinal Trematodes

Question 1

A 36-year-old man who has traveled for several weeks in the orient is experiencing abdominal pain and diarrhea with a large amount of mucus.A H.heterophyes egg measuring 28 by 15 µm is identified in the stool.The treatment of choice for this intestinal trematode is:

A)metronidazole.
B)chloroquine.
C)albendazole.
D)praziquantel.

Answer 1

D
The drug of choice for treatment of this intestinal trematode infection caused by H.heterophyes is praziquantel (Biltricide),an isoquinoline derivative administered orally in three doses for 1 day.Some mild side effects may develop,but these usually disappear within 48 hours and may be more severe in those with heavy infections.An alternative drug is niclosamide (Niclocide),which is administered for 1 to 2 days.

Question 2

The Heterophyes heterophyes worm,which has a genital sucker that surrounds the genital pore,has a variety of reservoir hosts including dogs,cats,and birds and a second intermediate host of freshwater:

A)snails.
B)fish.
C)crabs.
D)shrimp.

Answer 2

B
Adult H.heterophyes worms range in size from 1.0 to 1.7 mm in length and 0.3 to 0.4 mm wide and have a broadly rounded posterior.The adult H.heterophyes also has an additional sucker,the genital sucker,which surrounds the genital pore.H.heterophyes is found in China,Egypt,India,Iran,Israel,Japan,Korea,Sudan,Taiwan,the Philippines,Tunisia,and Turkey.Reservoir hosts include cats,dogs,and birds,and a variety of freshwater fish may serve as the second intermediate host.

Question 3

The life-cycle stages of the intestinal trematodes after the eggs are shed from the body via feces are best described as:

A)cercariae,miracidium larva,metacercariae,and redia.
B)redia,metacercariae,cercariae,and miracidium larva.
C)miracidium larva,redia,cercariae,and metacercariae.
D)metacercariae,miracidium larva,cercariae,and redia.

Answer 3

C
The adult worms are located in the small intestine,where they lay eggs,which may be embryonated or remain unembryonated until they are shed from the body via feces.The egg continues developing after reaching the water,and a ciliated,free-swimming miracidium larva is released.The miracidium enters a snail host and develops into a redia,followed by development into a tailed cercaria.The cercariae emerge from the snail and encyst as a metacercariae on water plants or fish.

Question 4

The adult form of the fluke,Fasciolopsis buski,is elongated in shape and ranges from 20 to 75 mm long and 8 to 20 mm wide with an oral sucker at the anterior and a ventral sucker approximately midway to the posterior.The reservoir host for the fluke is:

A)snails.
B)birds.
C)rodents.
D)dogs.

Question 5

The intermediate host of the Platyhelminthes is freshwater:

A)fish.
B)snails.
C)crabs.
D)crayfish.