chapter 23

Giardiasis is one of the more common GI diseases in the United States. Both animals and humans are at risk for developing this disease. In which of these cases would a human be most likely to become infected by this pathogen

A family hiking in the woods allows its dog to drink from a nearby stream. When they return home, the dog becomes sick with diarrhea in the house and family members must clean up the mess

Would a person living in Canada be able to contract malaria from a mosquito bite

A person living in Canada would not be likely to contract malaria from a mosquito bite because Plasmodium falciparum cannot complete its life cycle at a temperature below 20 degrees C

The tsetse fly is responsible for the spread of

African sleeping sickness

The largest nematode parasite of humans is

Ascaris lumbricoides

Triatoma, commonly called "kissing bugs," are vectors of

Chagas' disease

The protozoan (Cyclospora/Cryptosporidium/Echinococcus) can occasionally be transmitted from person to person

Cryptosporidium

Entamoeba histolytica can cause keratitis if it is introduced through an abrasion in the conjunctiva

False

Which species of Plasmodium typically causes the most serious disease

P. falciparum

Which of the following regarding all of the tapeworms that infect humans is TRUE

They all have non-human intermediate hosts

Anemia is a common consequence of hookworm infestation

True

Several species of Plasmodium cause malaria in humans

True

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

changes its glycoprotein surface antigens every time it replicates

Balantidium coli uses ________ to penetrate the intestinal mucosa

cilia

Which of the following is correctly matched

definitive host: mature forms reproduce

The most severe form of malaria, called "blackwater fever" is caused by Plasmodium(falciparum/malariae/ovale/vivax)

falciparum

Trypanosoma cruzi is introduced into the body by

feces containing trypomastigotes contaminating a bite wound

The primary risk to humans infected with Echinococcus granulosus is

formation of hydatid cysts.

The helminth parasite Schistosoma

has snails as intermediate hosts

Cycles of fever which recur every 48 hours is characteristic of

malaria

A housefly can transmit diseases as a (biological/fomite/mechanical) vector

mechanical

In cestodes, gravid proglottids are found __________

near the end of the strobila

The protozoans known as apicomplexans

reproduce by schizogony and are intracellular parasites.

Apicomplexans reproduce asexually by (mitosis/schizogony/fission

schizogony

The easiest way to prevent Taenia infection in humans is to

thoroughly cook or freeze meat

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

trophozoite

Which of the following is an accidental parasite of humans

Acanthamoeba

Corneal replacement is sometimes necessary as a result of which of the following diseases

Acanthamoeba keratitis

Blood smears are used in diagnosis of

African sleeping sickness and malaria

Which of the following helminth parasites do humans acquire by eating undercooked saltwater fish

Anisakis

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

Balantidium

Humans are the only reservoir for (Balantidium/Entamoeba/Giardia), an intestinal parasite that causes diarrhea.

Entamoeba

Which of the following is transmitted by the fecal-oral route

Entamoeba histolytica

Which of the following is the most common parasitic worm in the United States

Enterobius vermicularis

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

Even though it can be transmitted across the placenta, it is harmless to the fetus

All nematodes are acquired by ingestion

False

Contact with infected cats and their feces is the only mode of transmission of Toxoplasma to humans

False

Plasmodium reproduces by binary fission

False

The vectors of ________ are sand flies

Leishmaniasis

To diagnose giardiasis, microscopic evaluation is required and it is often hard to diagnose. Why do you think this is so?

Multiple stool samples are required to diagnose giardiasis because the cysts and trophozoites are shed only intermittently

Acanthamoeba and (Entamoeba/Naegleria/Plasmodium) cause rare and usually fatal infections of the brain

Naegleria

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

Naegleria

There are four species of Plasmodium that cause the disease malaria, of which P. falciparum is the most virulent. P. falciparum is transmitted by a mosquito vector to a human host. Can all mosquitoes transmit malaria? Why or why not

Only female Anopheles mosquitoes can transmit the malarial parasite to a human host because they are the only ones who take a blood meal from the host

Why is snail fever a common name for infections with Schistosoma

Snails are the intermediate host

Which of the following phases of infection occurs in the mosquito

Sporogonic phase

A human fecal sample is examined and found to contain a few strobila. The person is probably infected with

Taenia

Malaria used to be endemic in the U.S., but has not been prevalent for decades. How is this possible

The U.S. initiated a mosquito eradication program

The main symptoms of malaria are cycles of fever, anemia, and fatigue. During which stage of malaria would these symptoms be most apparent

The erythrocytic phase of the life cycle is most likely to cause these symptoms

Which vector is required for the spread of malaria

The female Anopheles mosquito

In the life cycle of Giardia intestinalis, the small intestine plays a pivotal role. What is the importance of the small intestine in the development of giardiasis

The small intestine is where the Giardia cyst releases the trophozoite and it can adhere to the epithelial cells and begin to multiply

What is a characteristic shared by the protozoa which are intestinal parasites of humans

They have a dormant cyst stage

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

Trichomonas

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

Trichomonas infection

The presence of active motile multi-flagellated trophozoites in vaginal or urethral secretion is indicative of infection with

Trichomonas vaginalis

All tapeworms are intestinal parasites that completely lack digestive systems

True

Balantidium coli is the only ciliate known to cause disease in humans

True

Herbivores are the normal hosts for Fasciola species

True

Humans can be accidental intermediate hosts for some tapeworms

True

Which of the following nematodes can be transmitted by mosquitoes

Wuchereria bancrofti

Which of the following groups of protozoan parasites is typically nonmotile

apicomplexans

The parasites classified as Nematodes

are known as roundworms

The most common nematode infection worldwide is (ascariasis/filariasis/pinworms

ascariasis

Diagnosis of malaria relies on identification of trophozoites in a __________

blood smear

Which of the following intestinal protozoa are considered parasites of humans only

both Entamoeba histolytica and Cyclospora cayentanensis

The definitive hosts for Echinococcus granulosus are

canines

The infectious stage of a beef tapeworm for humans is the

cysticerci in beef

Episodes of fever in a patient with malaria coincide with which of the following events

erythrocyte lysis

Elephantiasis is caused by

filarial roundworms

The only helminth disease of humans spread by an insect vector is

filariasis

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

giardiasis

The (brain/heart/liver) is the organ most severely damaged by Trypanosoma cruzi

heart

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

helminths

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

importance of early diagnosis and treatment

The number of cases of schistosomiasis has decreased over the past few decades due to which of the following

improvement in water systems

Humans become infected with Fasciola by

ingesting cysts on vegetation

Humans become infected with Toxoplasma gondii primarily by

ingesting meat containing the parasite

The (definitive/intermediate/primary) host is where immature stages of parasites develop

intermediate

All of the following diseases can be diagnosed from stool samples except__________

leishmaniasis

Which of the following arthropod vectors may spend its entire lifetime in association with a single individual

lice

The salivary glands of a tsetse fly will contain which of the following forms of Trypanosoma brucei

mature infective forms

Humans become infested with liver flukes by ingesting the (cercaria/metacercaria/miricidium) stage of the worm

metacercaria

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

mosquito

Which of the following is the most important arthropod vector of human diseases

mosquitoes

Eating undercooked (fish/pork/snails/vegetables) can result in infestation with Taenia solium

pork

Which of the following contributes to infection with Trichomonas vaginalis

preexisting disease (chlamydia, for example

The release of large quantities of merozoites into circulation at one time is due to a form of reproduction by Plasmodium known as __________

schizogony

The (proglottid/scolex/strobila) of an adult tapeworm is its anchor to the hosts intestine

scolex

Which of the following poses the greatest risk of contracting schistosomiasis

swimming in contaminated water

Which of the following phases of malaria occurs in humans

the erythrocytic cycle

The (cestodes/nematodes/trematodes) are helminths with an incomplete digestive system

trematodes

The _____ form of the parasite has a characteristic "ring" shape

trophozoite

Which of the following is necessary for successful xenodiagnosis of Chagas' disease

uninfected vectors

What method is the LEAST effective for controlling malaria

vaccination against P. falciparum

The protozoal disease known as (cutaneous/mucocutaneous/visceral) leishmaniasis is potentially fatal

visceral

Which type of leishmaniasis is most likely fatal

visceral leishmaniasis

The definitive host of a parasite is

where the mature form of the parasite occurs