Protozoa I

Question 1

Historically, medical parasitology has been divided into what three categories?

Answer 1

• Protozoa: single-celled eukaryotes
• Helminths: worms
• Arthropods: insects

Question 2

For those in the U.S., parasitic diseases affect ______________.

Answer 2

(1) those who travel to endemic areas; (2) poorer areas with unsanitary water, such as Appalachia

Question 3

Amoebiasis is caused by ________________.

Answer 3

Entamoeba histolytica

Question 4

Give the Sketchy rundown on E. histolytica.

Answer 4

• Intestinal parasite (like the haustra pipe)
• Causes bloody diarrhea (like the red stools)
• Can migrate to liver and cause liver abscess (like the liver-shaped excavation site with the dug-out holes)
• Treated with paramycin (pair of mice running out of the hole), metronidazole (subway), or iodoquinol (Iodos Queen head)
• Can lead to anchovy-paste pus in liver
• Fecal-oral transmission of cysts (bubbling water)
• Common in MSM community (guys holding hands)
• Flask-shaped ulcers in the colon (rust on the inside of haustra pipe)

Question 5

One of the things Sketchy didn’t mention about E. histolytica is that _________________.

Answer 5

it can spread to tissues other than the liver (such as the lungs or brain)

Question 6

The “flask” shape refers to _____________.

Answer 6

the histological sectioning of an ulcer

Question 7

Why can’t the trophozoite form of E. histolytica infect others?

Answer 7

Only the cyst form can survive outside the body.

Question 8

E. histolytica is able to spread so well because ________________.

Answer 8

only about 10% of carriers have symptoms

Question 9

Giardia lamblia typically infects the ___________ intestine.

Answer 9

small

Remember that invasive diarrhea infects the large intestine and noninvasive diarrhea (like Giardia) invades the small intestine.

Question 10

What are the symptoms of Giardia?

Answer 10

• Steatorrhea (yellow stools on boat)

* Foul-smelling stools (guys pinching their noses on boat)

Question 11

The trophozoites of Giardia cause malabsorption by _________________.

Answer 11

blocking the absorptive surface

Question 12

Chlorination is not effective at killing ______________.

Answer 12

Giardia

Question 13

______________ has a high infectivity index, requiring as few as 10 cysts to develop infection.

Answer 13

Giardia

Question 14

The only intestinal protozoan that is intracellular is ________________.

Answer 14

Cryptosporidium

Question 15

Cryptosporidium causes _____________ diarrhea.

Answer 15

watery

Question 16

Why is water filtration necessary for prevention of Cryptosporidium?

Answer 16

Because chlorination cannot kill it

Question 17

Why don’t Trichomonas vaginalis get transmitted in water?

Answer 17

Because the trophozoites cannot survive outside the human host and there is no cyst form of Trichomonas.

Thus, they can be transmitted sexually but that’s it.

Question 18

Which amoeba causes less severe meningoencephalitis?

Answer 18

Acanthomoeba

It causes chronic granulomatous encephalitis, keratitis, and skin ulcers.

Question 19

How can you diagnose Naegleria fowleri?

Answer 19

CSF wet mount showing trophozoites

Question 20

Naegleria fowleri is present in 70% of U.S. lakes. _____________ increases risk of infection.

Answer 20

Diving (which forces water up the nose)

Question 21

Which protozoa causes a flu-like illness on initial infection?

Answer 21

Toxoplasma gondii

Although, like with many infectious diseases, most infected people are asymptomatic.

Question 22

There are three ways to get infected with Toxoplasma: ____________________.

Answer 22

cysts from cat feces; cysts in meat; congenital infection

Question 23

What is the vulnerable window for maternal infection with Toxoplasma?

Answer 23

From six months prior to infection up to the third trimester

Question 24

What does congenital Toxoplasmosis cause?

Answer 24

• Hydrocephalus (cat with fishbowl on head)
• Deafness (cat that looks like Beethoven)
• Ventricular calcifications (cat with milk on head)
• Chorioretinitis (flash with retinal pattern)
• Hepatosplenomegaly

Question 25

Protozoa just means ______________.

Answer 25

unicellular eukaryotes

Question 26

Define definitive host.

Answer 26

The organism that harbors the sexually mature parasite

Question 27

Antibodies to invasive __________ are often used for diagnosis.

Answer 27

E. histolytica

Question 28

Giardia cysts break open upon ______________.

Answer 28

contact with stomach acid

Question 29

How common is Cryptosporidium?

Answer 29

750,000 cases per year in the U.S.

Question 30

_____________ is the only ciliate that infects humans.

Answer 30

Balantidium

Question 31

______________ is thought to be spread in swimming pools because asymptomatic people can pass it and chlorination doesn’t kill it.

Answer 31

Cryptosporidium