Deck 57: Blood Trematodes

Question 1

The only intermediate host required in the life cycle of blood flukes is a:

A) copepod.
B) crustacean.
C) freshwater snail.
D) freshwater fish.

Answer 1

C
Blood flukes differ in morphologic and life-cycle characteristics from the other trematodes; however, because they all belong to the same genus, they are similar and may be difficult to distinguish from each other.They do, however, require a freshwater snail as the only intermediate host.

Question 2

Rodents, marsupials, and nonhuman primates are all reservoirs for which Schistosoma species?

A) S. japonicum
B) S. haematobium
C) S. mansoni
D) S. intercalatum

Answer 2

D
S.intercalatum is primarily found in central and western Africa.Reservoirs include rodents, marsupials, and nonhuman primates.

Question 3

The eggs of the blood fluke Schistosoma haematobium range from 110 to 170 microns long by 40 to 70 microns wide and have a sharp, pointed terminal spine.In which specimen is this organism most likely found?

A) Ascites fluid
B) Sputum
C) Bile
D) Urine

Answer 3

D
The size range for eggs of S.haematobium is 110 to 170 microns long by 40 to 70 microns wide, and they have a sharply pointed terminal spine.They are fully embryonated without an operculum.In human infection, the adult worms live in the veins that supply the urinary bladder (S.haematobium).The eggs are passed from the body in either the feces or urine.

Question 4

An egg of the organism of Schistosoma mansoni is isolated from the feces of an adult man who has been traveling in Africa.An unoperculated egg with a large lateral spine is recovered.The patient is administered the standard dose of praziquantel; however, his infection does not improve.Which one of the following statements explains this discrepancy?

A) Metrifonate should have been administered.
B) Bilarcil is the drug of choice for this type of infection.
C) Steroids should have been initially administered.
D) A larger dose may be required to be effective against this organism.

Question 5

A large lateral spine is characteristic of which Schistosoma egg?

A) S. mansoni
B) S. japonicum
C) S. haematobium
D) S. mekongi