Question 1

The protozoans known as apicomplexans

Accepted Answer

Apicomplexans reproduce through schizogony and are intracellular parasites. They are unable to move on their own and rely on host cells for motility.

Question 2

Severe frothy diarrhea with a "rotten-egg" smell accompanied by abdominal pain,bloating,and fever are signs and symptoms consistent with

Accepted Answer

Severe frothy diarrhea with a "rotten-egg" smell accompanied by abdominal pain, bloating, and fever are classic symptoms of giardiasis, which is caused by the protozoan parasite Giardia lamblia. Balantidiasis presents with similar symptoms, but the diarrhea is not usually frothy and does not have a distinct odor. Chagas' disease, cryptosporidiosis, and leishmaniasis do not typically present with diarrhea as a primary symptom.

Question 3

Which of the following is a ciliated pathogen of the intestinal tract?

Accepted Answer

Balantidium is a ciliated protozoan pathogen that resides in the intestinal tract of infected humans and animals. Plasmodium, Trypanosoma, Leishmania, and Giardia are not ciliated pathogens of the intestinal tract, but rather cause malaria, sleeping sickness, leishmaniasis, and giardiasis, respectively.

Question 4

Which of the following organisms can colonize the nasal cavity and enter the brain to cause meningoencephalitis?

Accepted Answer

Naegleria is the only organism among the listed options that can colonize the nasal cavity and enter the brain to cause meningoencephalitis. Acanthamoeba and Entamoeba histolytica can cause brain infections but do not enter through the nasal cavity. Balantidium and Giardia do not cause brain infections.

Question 5

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?

Accepted Answer

The symptoms of anemia, weight loss, fever, and a recently healed sore near the nose are consistent with cutaneous leishmaniasis, a parasitic infection caused by the protozoan Leishmania. Microscopic examination of blood smears typically does not reveal the presence of the parasite. Malaria, Chagas disease, giardiasis, and balantidiasis do not fit the described symptoms or lesion location.

Question 6

The definitive host of a parasite is

Accepted Answer

The definitive host of a parasite is the host in which the mature form of the parasite occurs and where it reproduces sexually. This is distinct from intermediate hosts or vectors, which may host immature or dormant forms of the parasite.

Question 7

The ________ spreads more parasitic diseases to humans than any other vector.

Accepted Answer

Mosquitoes are known to spread many parasitic diseases such as malaria, dengue fever, Zika virus, and West Nile virus, among others. While other vectors such as ticks and lice also spread diseases, mosquitoes have a wider range and greater ability to transmit diseases to humans.

Question 8

Which of the following is the same for both Trypanosoma cruzi and Trypanosoma brucei?

Accepted Answer

Both Trypanosoma cruzi, which causes Chagas disease, and Trypanosoma brucei, which causes African sleeping sickness, require early diagnosis and treatment to prevent severe health consequences and improve the chances of a successful outcome.

Question 9

Which of the following parasites is not generally microscopic in its mature form,even though microbiologists usually study them?

Accepted Answer

Helminths are not generally microscopic in their mature form. They include parasitic worms such as tapeworms, flukes, and roundworms, which can be seen with the naked eye or with the help of a microscope. Amoebae, toxoplasmas, leishmanias, and cyclosporas are all typically microscopic parasites.

Question 10

Which of the following is the most common parasitic disease in industrialized nations?

Accepted Answer

Trichomonas infection, caused by the parasite Trichomonas vaginalis, is the most common parasitic disease in industrialized nations, primarily transmitted through sexual contact.

Question 11

The infectious stage of a beef tapeworm for humans is the

Accepted Answer

The infectious stage of a beef tapeworm for humans is the cysticerci (larval form) in beef. The cysticerci contain the infective stage of the tapeworm, which can mature into an adult tapeworm in the human intestine. The other options (A, B, C, and E) either represent non-infectious stages of the tapeworm or stages that are not directly infective to humans.

Question 12

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?

Accepted Answer

Acanthamoeba is a protozoan parasite that is commonly found in soil, water, and air. It can cause a rare but serious infection called Acanthamoeba keratitis (AK), which primarily affects contact lens wearers. The symptoms of AK include redness, pain, and inflammation of the eye, as well as ulceration of the conjunctiva. The other parasites listed do not typically cause eye infections or conjunctival ulceration.

Question 13

Once infected with Trypanosoma brucei,the patient's immune system cannot clear the infection and develop immunity because the parasite

Accepted Answer

Trypanosoma brucei changes its glycoprotein surface antigens every time it replicates, which allows it to evade the immune system and continue to cause infection. This mechanism is known as antigenic variation and makes it difficult for the immune system to recognize and develop immunity against the parasite.

Question 14

The ________ stage of a protozoan is the actively feeding and reproducing stage.

Accepted Answer

The trophozoite stage is characterized by active feeding and reproduction in protozoans. This stage is responsible for the growth and maintenance of the protozoan population.

Question 15

Which of the following species of Plasmodium causes cerebral malaria?

Accepted Answer

Only P. falciparum causes cerebral malaria. The other species of Plasmodium may cause severe malaria but not necessarily involving the brain.

Question 16

Which of the following is an accidental parasite of humans?

Accepted Answer

Acanthamoeba is an accidental parasite of humans, meaning it does not usually infect humans but can do so in rare situations such as through contact lens use or exposure to contaminated water. The other choices are not accidental parasites as they commonly infect humans.

Question 17

The presence of active motile multiflagellated trophozoites in vaginal or urethral secretion is indicative of infection with

Accepted Answer

Trichomonas vaginalis is a sexually transmitted protozoan parasite that infects the urogenital tract, causing trichomoniasis. It can be identified by the presence of active motile multiflagellated trophozoites in vaginal or urethral secretion upon microscopy. Chlamydia trachomatis, Giardia intestinalis, Acanthamoeba, and Balantidium coli are not sexually transmitted and do not typically infect the urogenital tract.

Question 18

Which of the following statements concerning infection with Toxoplasma is FALSE?

Accepted Answer

This statement is false. Toxoplasma can cause serious harm to the fetus if a pregnant woman is infected, and this can lead to serious birth defects or even stillbirth. It is important for pregnant women to take precautions to prevent infection with toxoplasmosis.

Question 19

Trypanosoma cruzi is introduced into the body by

Accepted Answer

Trypanosoma cruzi is transmitted to humans by contact with feces of triatomine bugs, which contain trypomastigotes. This can happen when the bug bites a person, and during or after feeding, the bug defecates near the bite wound, contaminating the site with the parasite.

Question 20

Which of the following parasitic infections can be diagnosed using a blood smear?

Accepted Answer

Both African sleeping sickness and malaria can be diagnosed using a blood smear. Toxoplasmosis is usually diagnosed by serological testing, not blood smear examination.

Quiz 23: Parasitic Protozoa, Helminths, and Arthropod Vectors