Deck 45: Overview of the Methods and Strategies in Parasitology

Question 1

The concentration protocol of the ova and parasite (O&P)examination:

A)requires freshly passed,unpreserved stool.
B)is designed to allow the detection of protozoan cysts,coccidian oocysts,microsporidial spores,and helminth eggs and larvae.
C)is microscopically examined at low,high dry,and oil immersion magnifications.
D)is designed to facilitate the identification of intestinal protozoa.

Answer 1

B
The O&P examination is made up of three separate protocols: (1)the direct wet mount, (2)the concentration,and (3)the permanent stained smear.The second part of the O&P examination is the concentration,which is designed to facilitate the recovery of protozoan cysts,coccidian oocysts,microsporidial spores,and helminth eggs and larvae.Both flotation and sedimentation methods are available;the most common procedure is the formalin-ethyl acetate sedimentation method (formerly called the formalin-ether method).The concentrated specimen is examined as a wet preparation,with or without iodine,using low and high dry magnifications (100×,400×)as indicated for the direct wet smear examination.

Question 2

The parasite T.gondii is acquired via the ingestion of infected oocysts from cat feces.A diagnosis is primarily made through:

A)examination of stool.
B)examination of blood films.
C)observance of "jerky" motility.
D)serologic means.

Answer 2

D
Infection caused by T.gondii,a tissue protozoon,is acquired via the ingestion of infected meat,the ingestion of oocysts from cat feces,transplacental transmission,blood transfusions,or organ transplantation.The diagnosis of toxoplasmosis is primarily made through serologic means,rather than through the identification of the organisms observed in human clinical specimens.

Question 3

A bone marrow aspirate is examined for the presence of parasites from a patient who has been traveling in Latin America for several months and who came in contact with a triatomid bug.Which parasite will most likely be identified?

A)Trypanosoma cruzi
B)D.fragilis
C)Fasciola hepatica
D)Chilomastix mesnili

Answer 3

A
Bone marrow aspirates for Leishmania and T.cruzi amastigotes,or Plasmodium spp. ,require staining using any of the bloodstains (e.g. ,Giemsa,Wright's,Wright-Giemsa,rapid stains,Field).The examination of specimens may confirm an infection previously missed by examination of routine blood films.The transmission of T.cruzi is through the infected feces of the triatomid bug.The bug takes a blood meal and immediately defecates,and the human host scratches the infected feces into the bite site.Bug saliva contains an irritant that stimulates scratching.

Question 4

The PARA-TECT Cryptosporidium/Giardia test kit uses which of the following formats for detection?

A)Direct fluorescent antibody (DFA)
B)Indirect fluorescent antibody (IFA)
C)Enzyme immunoassay (EIA)
D)Probe

Question 5

The eggs of which of the following intestinal parasites are not commonly found in feces and must be detected by other diagnostic techniques?

A)Giardia lamblia
B)Cryptosporidium parvum
C)Clonorchis sinensis
D)Enterobius vermicularis

Question 6

A modified acid-fast stain is performed on lung tissue.The most likely organism that will be observed is:

A)N.fowleri.
B)Mansonella streptocerca.
C)G.lamblia.
D)Cryptosporidium spp.

Question 7

This protozoa has a trophozoite stage but no cyst stage and reproduces via longitudinal binary fission.The parasite belongs to which category?

A)Amebae
B)Flagellates
C)Ciliates
D)Microsporidia

Question 8

Which of the following intestinal parasites is found in humans and also in pigs?

A)G.lamblia
B)D.fragilis
C)Cryptosporidium spp.
D)Balantidium coli

Question 9

The Entero-Test Capsule technique involves the collection of duodenal contents to examine the presence of which of the following parasites?

A)T.gondii
B)Giardia duodenalis
C)Entamoeba histolytica
D)Trichinella spiralis

Question 10

The permanent stained smear protocol of the O&P examination:

A)requires freshly passed,unpreserved stool.
B)is designed to allow the detection of protozoan cysts,coccidian oocysts,microsporidial spores,and helminth eggs and larvae.
C)is microscopically examined at low,high dry,and oil immersion magnifications.
D)is designed to facilitate the identification of intestinal protozoa.

Question 11

Some strains of leishmaniae have reservoir hosts,including dogs and wild rodents.Transmission is via the bite of a:

A)tsetse fly.
B)tick.
C)sandfly.
D)triatomid bug.

Question 12

Wuchereria,Brugia,Loa,and Onchocerca are all classified as:

A)intestinal cestodes.
B)tissue nematodes.
C)filarial nematodes.
D)blood trematodes.

Question 13

A 4-year-old boy who is in day care 3 days per week is irritable and scratching the area around his anus.What morphologic characteristics would most likely be observed on microscopic examination of the appropriate specimen?

A)Large eggs,proglottid shape
B)Large eggs with a terminal spine
C)Two individual hooklets
D)Football-shaped eggs with one flattened side

Question 14

A medical laboratory scientist (MLS)is examining a thin blood film from a patient suspected of having a Plasmodium infection.After examining the slide for 5 minutes and viewing approximately 100 oil immersion fields,the MLS does not observe any structures associated with Plasmodium.Which one of the following statements explains this discrepancy?

A)The stain may have been contaminated.
B)The MLS should have examined each field under high dry magnification;therefore the magnification is not correct.
C)The MLS may have missed the organism;more than 300 fields should be viewed.
D)No discrepancy is present.Plasmodium spp.are not found in blood;therefore the results are accurate.

Question 15

A 7-year-old girl was at summer camp and dove into the lake many times.She complained that water went up her nose a few times.Several days later she is unresponsive and comatose and rushed to the hospital.A cerebrospinal fluid (CSF)specimen is drawn,and several motile amebae are observed.She is most likely suffering from an infection with which of the following parasites?

A)Plasmodium vivax
B)Naegleria fowleri
C)Ascaris lumbricoides
D)Hymenolepis nana

Question 16

Babesia spp.is transmitted via the bite of a tick and can cause severe disease in patients who have been splenectomized or who are immunocompromised.To diagnose accurately these patient populations,the specimen of choice is:

A)stool.
B)urine.
C)genital sample.
D)blood.

Question 17

A urine sample from a 26-year-old woman is examined,and an organism is observed that displays "jerky" motility.This organism is classified as a(n):

A)amebae.
B)coccidia.
C)flagellate.
D)ciliate.

Question 18

The specimen of choice to collect in suspected cases of Paragonimus infection is:

A)sputum.
B)blood.
C)urine.
D)stool.

Question 19

A 17-year-old male with a severe eye infection admits that he does not clean his contact lenses as often as he should.His eye infection is most likely the result of which parasite?

A)Toxoplasma gondii
B)Isospora belli
C)Strongyloides stercoralis
D)Acanthamoeba spp.

Question 20

Which of the following is currently the only fixative available that does not contain formalin,polyvinyl alcohol (PVA),or mercury?

A)Merthiolate-iodine-formalin (MIF)
B)Sodium acetate-acetic acid-formalin (SAF)
C)ECOFIX
D)TOTAL-FIX