Self-Instructional Text 7th Edition by
Leventhal and Cheadle QUESTIONS AND
CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2025
1. Which of the following parasites causes amebic dysentery?
A. Giardia lamblia
B. Entamoeba histolytica
C. Balantidium coli
D. Cryptosporidium parvum
Entamoeba histolytica is the primary protozoan responsible for invasive
amebiasis and dysentery.
,2. The diagnostic stage of Ascaris lumbricoides in stool is the:
A. Larval form
B. Adult worm
C. Fertilized egg
D. Cyst
Fertilized eggs of Ascaris are found in the stool and are the diagnostic
form.
3. Which organism is known for causing "traveler’s diarrhea"?
A. Giardia lamblia
B. Entamoeba coli
C. Trypanosoma brucei
D. Trichuris trichiura
Giardia lamblia is a common cause of travel-related diarrhea and is
acquired via contaminated water.
4. The vector for Trypanosoma cruzi is the:
A. Sandfly
B. Tsetse fly
C. Mosquito
D. Reduviid bug
, Trypanosoma cruzi is transmitted by the reduviid (kissing) bug, which
defecates infective trypomastigotes.
5. The infective form of Plasmodium to humans is the:
A. Merozoite
B. Schizont
C. Sporozoite
D. Gametocyte
Sporozoites are injected by the Anopheles mosquito and are the
infective form to humans.
6. A thick and thin blood smear is most useful in diagnosing:
A. Giardia infection
B. Malaria
C. Toxoplasmosis
D. Cryptosporidiosis
Malaria is diagnosed by identifying Plasmodium species in stained blood
smears.
7. Which parasite causes autoinfection?
A. Necator americanus