Chapter 23 Parasitic Protozoa, Helminths, and Arthropod Vectors
23.1 Multiple Choice Questions
1) Which of the following is an accidental parasite of humans?
A) Ascaris lumbricoides
B) Acanthamoeba
C) Balantidium coli
D) Entamoeba histolytica
E) Plasmodium
2) Which of the following organisms can colonize the nasal cavity and enter the brain to cause
meningoencephalitis?
A) Entamoeba histolytica
B) Acanthamoeba
C) Naegleria
D) Balantidium
E) Giardia
3) Which of the following is a ciliated pathogen of the intestinal tract?
A) Balantidium
B) Plasmodium
C) Trypanosoma
D) Leishmania
E) Giardia
4) Once infected with Trypanosoma brucei, the patient’s immune system cannot clear the
infection and develop immunity because the parasite
A) has flagella that allow it to travel all over the body.
B) matures into infectious trypomastigotes.
C) reproduces by binary fission.
D) changes its glycoprotein surface antigens every time it replicates.
E) invades the central nervous system.
5) Trypanosoma cruzi is introduced into the body by
A) feces containing trypomastigotes contaminating a bite wound.
B) the bite of a tsetse fly, which introduces the trypomastigotes into the body.
C) ingesting food contaminated with the parasite.
D) the bite of a sand fly that has ingested phagocytes containing the parasite.
E) wearing contact lenses cleaned with contaminated tap water.
6) The definitive host of a parasite is
A) the host for immature stages of the parasite.
B) where the mature form of the parasite occurs.
C) also the vector for the parasite.
D) the host that the parasite name is based on.
E) the host for the dormant stage of the parasite.
7) Which of the following is the same for both Trypanosoma cruzi and Trypanosoma brucei?
A) central nervous system infection
B) where the protozoan matures in the vector
C) type of arthropod vector
D) importance of early diagnosis and treatment
E) means of entry into the host
8) Which of the following is the most common parasitic disease in industrialized nations?
A) giardiasis
B) Trichomonas infection
C) schistosomiasis
D) toxoplasmosis
E) balantidiasis
9) The presence of active motile multiflagellated trophozoites in vaginal or urethral secretion is
indicative of infection with
A) Trichomonas vaginalis.
B) Chlamydia trachomatis.
C) Giardia intestinalis.
D) Acanthamoeba.
E) Balantidium coli.
10) The protozoans known as apicomplexans
A) are motile.
B) reproduce by schizogony.
C) are intracellular parasites.
D) are motile intracellular parasites.
E) reproduce by schizogony and are intracellular parasites.
11) Severe frothy diarrhea with a “rotten-egg” smell accompanied by abdominal pain, bloating,
and fever are signs and symptoms consistent with
A) balantidiasis.
B) Chagas’ disease.
C) cryptosporidiosis.
D) giardiasis.
E) leishmaniasis.
12) Which of the following species of Plasmodium causes cerebral malaria?
A) only P. falciparum
B) P. ovale and P. malariae
C) P. ovale and P. vivax
D) P. vivax and P. malariae
E) P. vivax, P. malariae, and P. vivax
13) Which of the following parasitic infections can be diagnosed using a blood smear?
A) African sleeping sickness
B) toxoplasmosis
C) malaria
D) African sleeping sickness and malaria
E) toxoplasmosis and malaria
14) The ________ spreads more parasitic diseases to humans than any other vector.
A) kissing bug
B) mosquito
C) tick
D) louse
E) mite
15) Which of the following statements concerning infection with Toxoplasma is FALSE?
A) It is one of the world’s most widely distributed protozoan parasites in humans.
B) It is typically contracted by eating undercooked meat.
C) Even though it can be transmitted across the placenta, it is harmless to the fetus.
D) The majority of infected people are asymptomatic.
E) It usually results in no permanent damage and is self-limiting.
16) Which of the following parasites is NOT generally microscopic in its mature form, even
though microbiologists usually study them?
A) amoebae
B) toxoplasmas
C) helminths
D) leishmanias
E) cyclosporas
17) After a trip to several South American countries, a middle-aged man becomes ill. He
becomes anemic, loses weight, and runs a fever. The clinician notes a recently healed sore near
his nose. Microscopic examination of a blood smear does not reveal anything other than the
anemia. What parasitic infection is consistent with this scenario?
A) malaria
B) leishmaniasis
C) Chagas’ disease
D) giardiasis
E) balantidiasis
18) A contact lens wearer and cat owner begins to experience problems with her eye. The eye is
inflamed and painful, and examination of the eye reveals that the conjunctiva is ulcerating.
Which of the following parasites is most likely responsible?
A) Acanthamoeba
B) Cryptosporidium parvum
C) Entamoeba histolytica
D) Toxoplasma gondii
E) Trypanosoma cruzi
19) The infectious stage of a beef tapeworm for humans is the
A) gravid proglottids in feces.
B) eggs in contaminated water.
C) larvae in feces.
D) cysticerci in beef.
E) mature worms.
20) The ________ stage of a protozoan is the actively feeding and reproducing stage.
A) trophozoite
B) cyst
C) cysticercus
D) encysted
E) merozoite
21) The easiest way to prevent Taenia infection in humans is to
A) vaccinate cows and pigs.
B) vaccinate humans who are in contact with cows and pigs.
C) spray pastures and grazing lands with toxins that kill the parasite.
D) thoroughly cook or freeze meat.
E) identify patients with cysticerci in their muscles.
22) A human fecal sample is examined and found to contain a few strobila. The person is
probably infected with
A) Echinococcus granulosus.
B) Giardia intestinalis.
C) Taenia.
D) Schistosoma.
E) Necator americanus.
23) A person reports to a clinic complaining of fever and abdominal pain. The abdomen is
swollen, and blood tests indicate liver damage. A stool sample is examined under a microscope
and found to contain eggs with a spine projecting from its surface. The indications are
consistent with infection with
A) Ancylostoma duodenale.
B) Enterobius vermicularis.
C) Echinococcus granulosus.
D) Schistosoma mansoni.
E) Taenia solium.
24) A stool sample contains eggs that are oval and have no evidence of a spine. This
observation is consistent with infestation with ________ species.
A) Fasciola
B) Wuchereria
C) Schistosoma
D) Taenia
E) Trypanosoma
25) Which of the following nematodes can be transmitted by mosquitoes?
A) Wuchereria bancrofti
B) Ascaris lumbricoides
C) Ancylostoma duodenale
D) Necator americanus
E) Enterobius vermicularis
26) Which of the following is the most common parasitic worm in the United States?
A) Taenia saginata
B) Echinococcus granulosus
C) Schistosoma mansoni
D) Enterobius vermicularis
E) Ascaris lumbricoides
27) The helminth parasite Schistosoma
A) is a cestode.
B) uses snails as an intermediate host.
C) has proglottids.
D) is a roundworm.
E) is a liver fluke.
28) Which of the following helminth parasites do humans acquire by eating undercooked
saltwater fish?
A) Schistosoma
B) Fasciola
C) Echinococcus
D) Anisakis
E) Ascaris
29) The parasites classified as Nematodes
A) are known as flukes.
B) are known as roundworms.
C) have males of the species larger than females of the species.
D) do not have a digestive system.
E) are all monoecious.
30) Humans become infected with Fasciola by
A) ingesting cysts on vegetation.
B) consuming cysticerci in contaminated meat.
C) ingesting water contaminated with eggs.
D) the penetration of cercariae through the skin.
E) the bite of infected mosquitoes.
31) Elephantiasis is caused by
A) blood flukes.
B) liver flukes.
C) filarial roundworms.
D) tapeworms.
E) flatworms.
32) Humans become infected with Toxoplasma gondii primarily by
A) being bitten by a tick.
B) direct skin penetration.
C) ingesting food or water contaminated with cysts.
D) ingesting meat containing the parasite.
E) intimate contact with another person.
33) A patient at a clinic complains of diarrhea that is occasionally bloody and has persisted for
several days. A microscopic examination of a stool sample reveals the presence of very round
cysts. These signs are consistent with infection by
A) Entamoeba histolytica.
B) Enterobius vermicularis.
C) Balantidium coli.
D) Giardia intestinalis.
E) Trypanosoma cruzi.
34) Which of the following is transmitted by the fecal-oral route?
A) Entamoeba histolytica
B) Plasmodium
C) Schistosoma
D) Trichomonas
E) Schistosoma and Trichomonas
35) What do Echinococcus granulosus, Entamoeba histolytica, and Enterobius vermicularis
have in common?
A) They are transmitted by insect vectors.
B) They live in the intestines of their definitive host.
C) They are intracellular parasites.
D) They cause zoonoses in humans.
E) They are diagnosed by examination of a blood smear.
36) The primary risk to humans infected with Echinococcus granulosus is
A) development of cysticerci.
B) formation of hydatid cysts.
C) intestinal obstruction.
D) anemia.
E) infection of the fetus.
37) Why is snail fever a common name for infections with Schistosoma?
A) The worms look like snails.
B) They are contracted by eating snails.
C) Snails are the intermediate host.
D) Physical contact with snails may result in infection.
E) The larval stage looks like a snail.
38) Balantidium coli uses ________ to penetrate the intestinal mucosa.
A) adhesion discs
B) flagella
C) cilia
D) pseudopodia
E) suckers
39) Triatoma, commonly called “kissing bugs,” are vectors of
A) African sleeping sickness.
B) Chagas’ disease.
C) Cyclosporiasis.
D) Leishmania.
E) schistosomiasis.
40) Which of the following intestinal protozoa are considered parasites of humans only?
A) Entamoeba histolytica
B) Balantidium coli
C) Cyclospora cayentanensis
D) Giardia intestinalis
E) both Entamoeba histolytica and Cyclospora cayentanensis
41) The tsetse fly is responsible for the spread of
A) African sleeping sickness.
B) Chagas’ disease.
C) filariasis.
D) kala-azar.
E) toxoplasmosis.
42) The only helminth disease of humans spread by an insect vector is
A) ascariasis.
B) fascioliasis.
C) filariasis.
D) hydatid disease.
E) schistosomiasis.
43) The vectors of ________ are sand flies.
A) beaver fever
B) Chagas’ disease
C) filariasis
D) giardiasis
E) leishmaniasis
44) Which of the following contributes to infection with Trichomonas vaginalis?
A) contact with contaminated fomites
B) compromised immunity
C) careless handwashing habits
D) preexisting disease (chlamydia, for example)
E) living in an undeveloped area of the world
45) Which of the following regarding all of the tapeworms that infect humans is TRUE?
A) They all have non-human intermediate hosts.
B) The larva can directly infect humans upon contact with skin.
C) Humans are the normal intermediate hosts.
D) They are transmitted by insect vectors.
E) They reside in the muscle tissue of the definitive host.
23.2 True/False Questions
1) Balantidium coli is the only ciliate known to cause disease in humans.
2) Contact with infected cats and their feces is the only mode of transmission of Toxoplasma to
humans.
3) All tapeworms are intestinal parasites that completely lack digestive systems.
4) All flukes are monoecious.
5) Plasmodium reproduces by binary fission.
6) Several species of Plasmodium cause malaria in humans.
7) Entamoeba histolytica can cause keratitis if it is introduced through an abrasion in the
conjunctiva.
8) Anemia is a common consequence of hookworm infestation.
9) Leishmania species cause systemic disease as well as superficial diseases.
10) Humans can be accidental intermediate hosts for some tapeworms.
23.3 Short Answer Questions
1) An intestinal parasite that is an emerging disease in North America,
(Cryptosporidium/Cyclospora/Entamoeba) causes a watery diarrhea with fever.
2) Acanthamoeba and (Entamoeba/Naegleria/Plasmodium) cause rare and usually fatal
infections of the brain.
3) The (brain/heart/liver) is the organ most severely damaged by Trypanosoma cruzi.
4) The (definitive/intermediate/primary) host is where immature stages of parasites develop.
5) Humans are the only reservoir for (Balantidium/Entamoeba/Giardia), an intestinal parasite
that causes diarrhea.
6) The parasite (Leishmania/Toxoplasma/Trichomonas) is an obligate parasite that is incapable
of surviving long outside the human host and is transmitted almost exclusively via sexual
activity.
7) The most severe form of malaria, called “blackwater fever” is caused by Plasmodium
(falciparum/malariae/ovale/vivax).
8) A housefly can transmit diseases as a (biological/fomite/mechanical) vector.
9) Apicomplexans reproduce asexually by (mitosis/schizogony/fission).
10) Damage to the (brain/heart/liver) is the primary result of fetal infection with Toxoplasma
gondii.
11) The most common nematode infection worldwide is (ascariasis/filariasis/pinworms).
12) The (cestodes/nematodes/trematodes) are helminths with an incomplete digestive system.
13) The (proglottid/scolex/strobila) of an adult tapeworm is its anchor to the hosts intestine.
14) Eating undercooked (fish/pork/snails/vegetables) can result in infestation with Taenia
solium.
15) Enterobius vermicularis are commonly known as (pinworms/hookworms/tapeworms)
because of the shape of the female’s tail.
23.4 Essay Questions
1) Parasitic diseases have been considered uncommon in developed countries but many are now
emerging diseases in these parts of the world. Discuss factors that contribute to this shift.
2) How does the life cycle for the Trypanosoma that causes sleeping sickness differ from the
one that causes Chagas’ disease?
3) A hunter was camping with his dog near a mountain spring where beavers were building a
dam, and many animals came to drink. After a month, he developed severe watery diarrhea,
abdominal pain, bloating, vomiting, and low-grade fever. His stool had a “rotten-egg” smell of
hydrogen sulfide. What is the most likely parasite causing this patient’s condition, and how is
diagnosis confirmed?
4) Why is self-reinfection commonly seen in children that suffer from pinworms?
5) Compare and contrast infection with Taenia saginata and Echinococcus granulosus in
humans, including the consequences of the infections.