Parasitology

Question 1

Describe Opisthorchis species.

Answer 1

Seeded operculum, knob opposite.

Question 2

How do you differentiate between hookworm and Strongyloides stercoralis infection?

Answer 2

Rhabditiform larvae. The opening in the rhabditiform larvae of S. stercoralis is extremely short, while the mouth opening in hookworm rhabditiform larvae is approximately three times as long.

Question 3

How do you distinguish Necator from Ancyclostoma in both the rhabditiform and adult stages?

Answer 3

Rhabditiform stages are indistinguishable. In the adult stages, N. americanus has cutting plates and A. duodenale has teeth.

Question 4

How would you diagnose Leishmania mexicana in a skin lesion?

Answer 4

Finding of amastigots, organism intracellular in macrophages, finding red kinetoplasts in cytoplasm.

Question 5

In preparation of thick and thin malarial smears, which smear is fixed and using what?

Answer 5

Thin smears are fixed using methanol

Question 6

In what specimen would you NOT find Trichmonas vaginalis?

Answer 6

Stool and blood

Question 7

What are the characteristics that would let allow you to diagnose a Trypanosoma cruzi infection?

Answer 7

C or U shape, nucleus in the center, kinetoplast at posterior end.

Question 8

What is the agent of cystericosis?

Answer 8

Larval Taenia solium (pork tapeworm)

Question 9

What is the ideal specimen for scabies?

Answer 9

Skin scraping

Question 10

What is the most common Plasmodium species in California?

Answer 10

Plasmodium vivax

Question 11

What is the purpose of the preservatives PVA and SAF?

Answer 11

Preservation of trophozoites

Question 12

What is the specimen for Trichomonas vaginalis?

Answer 12

Urine (troph state only)

Question 13

What is the specimen on choice for Acanthamoeba?

Answer 13

Corneal biopsy

Question 14

What parasite can caused autoinfection?

Answer 14

Strongyloides stercoralis

Question 15

What parasite has a troph stage greater than 10 microns with no peripheral chromatin bodies?

Answer 15

Endolimax nana

Question 16

When is blood drawn for a microfilaria infection?

Answer 16

At the time appropriate for the microfilaria you are trying to find.

Question 17

Which amoeba has ‘splintered’ chromatid bodies?

Answer 17

Entamoeba coli cysts

Question 18

Which Malarial infection is associated with Schuffner’s Dots?

Answer 18

Plasmodium ovale and Plasmodium vivax

Question 19

Which organism may not be visible or hard to see in a wet mount (not found in the concentrate tube)? Why?

Answer 19

Dientamoeba fragilis (it has no cyst stage).

Question 20

Which parasite is not present in stool?

Answer 20

Trichinella spiralis

Question 21

Which parasite’s eggs can be found in urine?

Answer 21

Schistosoma haematobium

Question 22

Which stain is not used to identify Cryptosporidium?

Answer 22

Auromine-Rhodamine

Question 23

Why is iodine used in parasitology examinations?

Answer 23

To better visualize internal structures.