Parasitology: Protozoa (Wilson)

Question 1

Which of the following statements about protozoa is FALSE?

A. They are unicellular organisms.

B. They require a human host to multiply.

C. Infections with these organisms are usually accompanied by eosinophilia.

D. They are susceptible to host immune defenses.

E. A very small inoculum can cause disease.

Answer 1

C

Question 2

Which of the following statements about human malaria is FALSE?

A. It is transmitted to humans through a mosquito bite.

B. It is caused by the Plasmodium spp. protozoa

C. Effective medication can achieve a sterile cure.

D. The best upcoming malaria vaccine is much more effective in preventing disease than naturally acquired immunity.

E. Plasmodium species are highly resistant to treatment.

Answer 2

D. The best upcoming vaccine acheives poor efficacy and is not any better than naturally acquired immunity, which is partial and transient.

Question 3

Which part of the Malaria life cycle is INCORRECT?

A. Infected mosquitos inject sporozoites into the bloodstream of human hosts, which then travel to the liver and divide.

B. Over 5-16 days, the sporozoites grow, divide, and produce tens of thousands of haploid merozoites (schizonts).

C. Merozoites (schizonts) rupture through liver cells and re-enter the bloodstream, beginning a cycle of invasion of RBCs, asexual replication, and release of newly formed merozoites.

D. Some of the merozoite-infected blood cells leave the cycle of asexual multiplication and instead of replicating, the merozoites in these cells travel back to the liver and develop into gametocytes.

E. When a mosquito bites an infected human, it ingests the gametocytes, which fuse and burrow into the mosquito midgut wall and form oocysts that release sporozoites.

Answer 3

D. Merozoites ithat have left the liver never go back and reinfect the liver - develop into sexual forms of the parasite in the bloodstream, where they are ingested by mosquitos that bite the infected host.

This is a great diagram of the malaria life cycle

Question 4

Antimalarials treat the ______ stage of the malaria cycle, and not the dormant _______, which remain in the liver and may cause relapsing infection.

Answer 4

erythrocytic; hypnozoites

Question 5

All of the following are clinical manifestations of malaria EXCEPT:

A. cyclic fever

B. fatigue

C. vomiting

D. headache

E. mono-like lymphadenopathy

Answer 5

E. This is a clinical feature of toxoplasmosis.

Question 6

this subspecies of Plasmodium is the most serious form because of its ability to cause erythrocytes to adhere to endothelium; it is distinguished on a blood smear by its banana-shaped gamtocytes:

Answer 6

P. falciparum

*this is the strain that causes organ damage and cerebral hemorrhage

Question 7

these two subspecies of Plasmodium are very similar-looking on a blood smear, but may be distinguished more easily in their trophozoite stage (developing schizont)

Answer 7

P. vivax and P. ovale

Question 8

What feature do P. vivax and P. ovale share on a blood smear, and what feature distinguishes them?

Answer 8

They both contain Schuffner’s dots in their cytoplasm; their shapes are slightly different, with vivax having a slightly more ameboid-looking trophozoite (see below)

Question 9

This strain of Plasmodium is the most mild and rare, affecting mature erythrocytes without affecting the cell architecture very much; it is distinct on a blood smear because of its unique darkly pigmented (hemozoin) trophozoite:

Answer 9

P. malariae

Question 10

these drugs is used to treat all species of Plasmodium except falciparum

Answer 10

chloroquines

Question 11

this drug can be used to treat Plasmodium in the hypnozoite stagein the liver, but is contraindicated in pregnancy and in patients with G6PD deficiency

Answer 11

primaquine

Question 12

combination therapy used to treat resistant P. falciparum

Answer 12

Malarone: atovaquone/proguanil

Or

Coartem: artemether-lumefantrine

Question 13

this organism is spread as an oocyst in cat stools, which is ingested directly or as a tissue cyst in meat causing widespread infection in humans

Answer 13

Taxoplasma gondii

Question 14

Which of these statements about Toxoplasmosis is FALSE?

A. Congenital toxoplasmosis causes disease in the fetus when the mother is first exposed during pregnancy.

B. Acute acquired toxoplasmosis may be asymptomatic or present as mono-like lymphadenopathy.

C. Acute and reactivation toxoplasmosis may cause CNS disease, pneumonitis, or myocarditis in the normal host.

D. Ocular toxoplasmosis may cause choroid or retinal cysts.

E. Encephalitis can occur in any immunocompromised host that contracts a Toxoplasma spp. organism.

Answer 14

C. Normal hosts are commonly asymptomatic. These symptoms are generally seen in the immunocompromsied.

Question 15

this disease is found in wild rodent and domestic dog reservoirs and is transmitted through the bite of the sand fly

Answer 15

leishmaniasis

Question 16

Which of the following statements regarding leishmaniasis is TRUE?

A. Mucocutaneous leishmaniasis is most common in Latin America and is self-limiting.

B. Painful ulcers with heaped up margins are characteristic of cutaneous leishmaniasis.

C. Fatalaties related to visceral leishmaniasis are usually due to splenic rupture.

D. All forms of leishmaniasis are fatal if left untreated.

E. Visceral leishmaniasis is characterized by invasion of intracellular parasites in the macrophages of the RES (spleen, liver, bone marrow)

Answer 16

E

Question 17

a disease caused by T. cruzi, which is transmitted via South American reduvvid bugs, and when chronic leads to heart damage and mega-syndrome

Answer 17

Chagas’ disease

Question 18

extraintestinal amoeba that is immediately infectious to the next host and causes liver abscess and pore formation in the gut, and may lead to severe invasive disease

Answer 18

• Entamoeba histolytica*
• *E. dispar* has much lower pathogenicity and is commonly spread by the fecal-oral route from person-to-person in daycare centers and families

Question 19

All of the following are similiarties between Giardia (don’t drink that refreshing-looking stream water in Colorado) and Cryptosporidium (don’t go to daycare in Milwaukee) EXCEPT:

A. They are both intestinal, non-inflammatory protozoa

B. They are both immediately infectious via direct spread

C. They are both resistant to chlorination, causing outbreak in municipal water supply

D. They are both treated with nitazoxanide

E. They are both acid fast organisms that can cause extraintestinal infections

Answer 19

E.

Cryptosporidium is an acid fast sporozoan that can cause extraintestinal infection. Giaria is a flagellate and is limited to the lumen of the GI tract.

Question 20

this organism must sporulate in the environment before it becomes infectious; there’s no antigen test available but it can be identified in stool samples via modified acid fast stain

Answer 20

Cyclospora cayetanensis (don’t eat Guatemalan raspberries)