8.11 Parasitology Flashcards by Laurita Z

The incorrect match between organism and the appropriate diagnostic procedure is:
A. Onchocerca volvulus — examination of skin snips
B. Cryptosporidium spp. —modified acid-fast stain
C. Enterobius vermicularis— routine ova and parasite examination
D. Schistosoma haematobium—examination of urine sediment

C. Enterobius vermicularis— routine ova and parasite examination

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In a patient with diarrhea, occasionally Entamoeba histolytica/E. dispar (four nucleated cysts, no chromatoidal bars) are identified as being present; however, these cells, which are misdiagnosed as protozoa, are really:
A. Macrophages
B. Polymorphonuclear leukocytes (PMNs)
C. Epithelial cells
D. Eosinophils

B. Polymorphonuclear leukocytes (PMNs)

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Charcot-Leyden crystals in stool may be associated with an immune response and are thought to be formed from the breakdown products of:
A. Neutrophils
B. Eosinophils
C. Monocytes
D. Lymphocytes

B. Eosinophils

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Parasitic organisms that may be transmitted sexually do not include:
A. Entamoeba gingivalis
B. Dientamoeba fragilis
C. Trichomonas vaginalis
D. Diphyllobothrium latum

D. Diphyllobothrium latum

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The incorrect match between the organism and one method of acquiring the infection is:
A. Trypanosoma brucei rhodesiense—bite of sand fleas
B. Giardia lamblia (G. intestinalis, G. duodenalis) — ingestion of water contamination with cysts
C. Hookworm — skin penetration of larvae from soil
D. Toxoplasma gondii—ingestion of infected raw or rare meats

A. Trypanosoma brucei rhodesiense—bite of sand fleas

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Upon examination of stool material for Cystoisospora belli, one would expect to see:
A. Cysts containing sporozoites
B. Precysts containing chromatoidal bars
C. Oocysts that are modified acid-fast positive
D. Sporozoites that are hematoxylin positive

C. Oocysts that are modified acid-fast positive

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Which specimen is the least likely to provide recovery of Trichomonas vaginalis?
A. Urine
B. Urethral discharge
C. Vaginal discharge
D. Feces

D. Feces

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Which of the following is the best technique to identify Dientamoeba fragilis in stool?
A. Formalin concentrate
B. Trichrome-stained smear
C. Modified acid fast-stained smear
D. Giemsa stain

B. Trichrome-stained smear

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One of the following protozoan organisms has been implicated in waterborne and foodborne outbreaks within the United States. The suspect organism is:
A. Pentatrichomonas hominis
B. Dientamoeba fragilis
C. *Giardia lamblia (G. intestinalis, G. duodenalis)
D. Balantidium coli

C. *Giardia lamblia (G. intestinalis, G. duodenalis)

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Gram staining of a sample from a gum lesion showed what appeared to be amoebae. A trichrome smear showed amoebae with a single nucleus and partially digested PMNs.
The correct identification is:
A. Trichomonas tenax
B. Entamoeba histolytica/Entamoeba dispar
C. Entamoeba gingivalis
D. Entamoeba polecki

C. Entamoeba gingivalis

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An *E. histolytica (true pathogen) trophozoite has the following characteristics:
A. Compact karyosome in the nucleus, ingested RBCs, and clear pseudopodia
B. Ingested RBCs, clear pseudopodia, and uneven chromatin on the nuclear membrane
C. Ingested RBCs, clear pseudopodia, and large glycogen vacuoles in cytoplasm
D. Large, blotlike karyosome, ingested white blood cells (WBCs), and granular pseudopods

A. Compact karyosome in the nucleus, ingested RBCs, and clear pseudopodia

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A 12-year-old girl is brought to the emergency room with meningitis and a history of swimming in a warm-water spring. Motile amoebae that measure 10 um in size are seen in CSF and are most likely:
A. Iodamoeba butschlii trophozoites
B. Endolimax nana trophozoites
C. Dientamoeba fragilis trophozoites
D. Naegleria fowleri trophozoites

D. Naegleria fowleri trophozoites

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Characteristics of the rhabditiform (noninfective) larvae of Stronglyloides stercoralis include a:
A. Short buccal capsule and large genital primordium
B. Long buccal capsule and pointed tail
C. Short buccal capsule and small genital primordium
D. Small genital primordium and notch in tail

A. Short buccal capsule and large genital primordium

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Visceral larva migrans is associated with which of the following organisms and diagnostic method?
A. Toxocara—serology
B. Onchocerca—skin snips
C. Dracunculus—skin biopsy
D. Angiostronglylus—CSF examination

A. Toxocara—serology

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The following organisms are linked with specific, relevant information. The incorrect combination is:
A. Strongyloides stercoralis—internal auto infection
B. Echinococcus granulosus—hydatid examination
C. Toxoplasma gondii— serology
D. Balantidium coli — common in the United States

D. Balantidium coli — common in the United States

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Examination of 24-hour unpreserved urine specimen is sometimes helpful in the recovery of:
A. Trichomonas vaginalis trophozoites
B. Schistosoma haematobium eggs
C. Enterobius vermicularis eggs
D. Strongyloides stercoralis larvae

B. Schistosoma haematobium eggs

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The examination of sputum may be necessary to diagnose infection with:
A. Paragonimus westermani
B. Trichinella spiralis
C. Wuchereia bancrofti
D. Fasciola hepatica

A. Paragonimus westermani

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Two helminth eggs that may resemble one another are:
A. Diphyllobothrium latum and Paragonimus westermani
B. Opisthorchis sinensis and Fasciolopsis buski
C. Taenia saginata and Hymenolepis nana
D. Ascaris lumbricoides and Trichostrongylus

A. Diphyllobothrium latum and Paragonimus westermani

Both D.latum and P. westermani eggs are operculated and approximately the same size. The morphology is similar, although D. latum has a knob at the abopercular end and P. westermani has a thickened abopercular end and shoulders into which the operculum fits.

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Eating poorly cooked infected pork can lead to an infection with:
A. Taenia solium and Trichinella spiralis
B. Taenia saginata and Hymenolepis nana
C. Trichuris trichiura and Hymenolepis diminuta
D. Diphyllobothrium latum and Ascaris lumbricoides

A. Taenia solium and Trichinella spiralis

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An operculated cestode egg that can be recovered from human feces is:
A. Clonorchis sinensis
B. Diphyllobothrium latum
C. Paragonimus westermani
D. Dipylidium caninum

B. Diphyllobothrium latum

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The adult tapeworm of Echinococcus granulosus is found in the intestine of:
A. Dogs
B. Sheep
C. Humans
D. Cattle

A. Dogs

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In infections with Taenia solium, humans can serve as the:
A. Definitive host
B. Intermediate host
C. Either the definitive or the intermediate host
D. None of the above

C. Either the definitive or the intermediate host

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Humans acquire infections with Diphyllobothrium latum adult worms by:
A. Ingestion of freshwater crabs
B. Skin penetration of cercariae
C. Ingestion of water chestnuts
D. Ingestion of raw freshwater fish

D. Ingestion of raw freshwater fish

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Humans can serve as both the intermediate and definitive host in infections caused by:
A. Enterobius vermicularis
B. Hymenolepis nana
C. Schistosoma japonicum
D. Ascaris lumbricoides

B. Hymenolepis nana

In infections with H. nana, humans serve as both intermediate and definitive hosts. When ingested, the oncosphere penetrates the intestinal mucosa, develops into the mature cysticercoid (human is intermediate host), and returns to the gut, where the adult tapeworm matures (human is definitive host). Thus, the life cycle can go from egg to adult tapeworm within the human host.

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**Babesia is an organism that has been implicated in disease from both splenectomized and nonsplenectomized patients. Morphologically, the parasites resemble:** A. *Plasmodium falciparum* rings B. *Leishmania donovani* amastigotes C. *Trypanosoma cruzi trypomastigotes* D. *Microsporidian* spores

A. *Plasmodium falciparum* rings ##Footnote Babesia is an intracellular parasite that closely resembles the ring forms (early trophozoites) of *P. falciparum*. Often in babesiosis there are more rings per cell and the ring form is the only stage seen.

** Organisms (and infections) that under normal conditions cannot be transmitted in the laboratory are:** A. Cryptosporidium—cryptosporidiosis B. Taenia solium—cysticercosis C. Ascaris lumbricoides— ascariasis D. Enterobius vermicularis—pinworm infections

C. Ascaris lumbricoides— ascariasis ##Footnote *A. lumbricoides* eggs require a period of development in the soil before they are infective for humans. The other organisms listed can be transmitted within the laboratory or in the hospital setting.

**Toxoplasma gondii is characterized by:** A. Possible congenital infection and ingestion of oocysts B. Cosmopolitan distribution and possible difficulties with interpretation of serological results C. None of the above D. Both A and B

D. Both A and B

**Oocysts of Cryptosporidium spp. can be detected in stool specimens by using:** A. Modified acid-fast stain B. Gram stain C. Methenamine silver stain D. Trichrome stain

A. Modified acid-fast stain ##Footnote Oocyst of Cryptosporidium spp. can be found and identified using microscopic examination of fecal smears stained with modified acid-fast stains. They appear as purple-red-pink round objects, measuring approximately 4 to 6 um. Often the four sporozoites and residual body can be seen with the oocyst wall.

**Which microfilariae are usually not found circulating in peripheral blood?** A. *Brugia malayi* B. *Wuchereria bancrofti* C. *Onchocerca volvulus* D. *Loa loa

C. *Onchocerca volvulus* ##Footnote *O.volvulus microfilariae are normally found in the fluid right under the outer layer of skin. Therefore, the skin snip is the proper specimen to examine.

**Massive hemolysis, blackwater fever, and central nervous system involvement are most common with:** A. *Plasmodium vivax* B. *Plasmodium falciparum* C. *Plasmodium ovale* D. *Plasmodium malariae*

B. *Plasmodium falciparum* ##Footnote The pathogenic sequelae of malarial infections with *P. falciparum* are the most severe of the four species listed. They can include massive hemolysis, blackwater fever, and multiple organ involvement, including the central nervous system (cerebral malaria).

**Organisms that should be considered in a nursery school outbreak of diarrhea include:** A. *Endolimax nana, Giardia lamblia (G. intestinalis, G. duodenails),* and *Entamoeba coli* B. *Giardia lamblia (G. intestinalis, G. duodenalis), Dientamoeba fragilis*, and *Cryptosporidium parvum* C. *Cryptosporidium* spp., *Trichomonas vaginalis*, and *Entamoeba coli* D. *Trichomonas hominis*, *Dientamoeba fragilis, and *Endolimax nana*

B. *Giardia lamblia (G. intestinalis, G. duodenalis), Dientamoeba fragilis*, and *Cryptosporidium parvum*

**The *incorrect* match between disease and symptoms is:** A. Paragonimiasis — hemoptysis B. Cryptosporidiosis — watery diarrhea C. Toxoplasmosis in compromised host — center al nervous system symptoms D. Enterobiasis — dysentery

D. Enterobiasis — dysentery ##Footnote Infections with *E. vermicularis* (the pinworm) may cause anal itching, sleeplessness, and possibly some vaginal irritation or discharge; however, dysentery (bloody diarrhea) has not been associated with this infection.

**The formalin-ether (ethyl acetate) concentration procedure for feces is used to demonstrate:** A. Motility of helminth larvae B. Protozoan cysts and helminth eggs C. Formation of amoebic pseudopods D. Trophozoites

B. Protozoan cysts and helminth eggs

**Cysts of *Iodamoeba butschlii* typically have:** A. Chromatoidal bars with rounded ends B. A heavily vacuolated cytoplasm C. A large glycogen vacuole D. Many ingested bacteria and yeast cells

C. A large glycogen vacuole

**The miracidial hatching test helps to demonstrate the viability of eggs of:** A. *Taenia species* B. *Schistosoma species* C. *Hookworm species* D. *Opisthorchis species*

B. *Schistosoma species* ##Footnote The determination of egg viability is important in schistosomiasis; therefore, the miracidial hatching test is helpful in demonstrating the egg viability of *Schistosoma* species. Once the eggs are hatched, the living miracidium larvae will be visible in the water.

**Organisms that should be considered in a waterborne outbreak of diarrheal disease include:** A. *Giardia lamblia (G. intestinalis, G. duodenalis)* and *Cryptosporidium* spp. B. *Endolimax nana* and *Entamoeba histolytica* C. *Blastocystis* spp. and *Trichomonas vaginalis* D. *Toxoplasma gondii* and *Schistosoma mansoni*

A. *Giardia lamblia (G. intestinalis, G. duodenalis)* and *Cryptosporidium* spp. ##Footnote Both G. lamblia (G. intestinalis, G. duodenalis) and Cryptosporidium have been implicated in waterborne outbreaks or diarrheal disease. These infections would result from the ingestion of Giardia cysts and/ or Crypotsporidium oocyst.

**Fecal immunoassays have become more commonly used to diagnose infections with:** A. *Endolimax nana* and *Blastocystis* spp. B. *Giardia lamblia (G. intestinalis, G. duodenalis)* and *Cryptosporidium* spp. C. *Ascaris lumbricoides* and *Trichuris trichiura* D. *Strongyloides stercoralis* and Trichomonas vaginalis*

B. *Giardia lamblia (G. intestinalis, G. duodenalis)* and *Cryptosporidium* spp.

**The most common infections with the microsporidia often originate in:** A. The lung B. The nervous system C. The gastrointestinal tract D. Mucocutaneous lesions

C. The gastrointestinal tract

**Eye infections with *Acanthamoeba* spp. have most commonly been traced to:** A. Use of soft contact lenses B. Use of hard contact lenses C. Use of contained lens care solution D. Failure to remove lenses while swimming

C. Use of contained lens care solution ##Footnote With the possible exception of direct inoculation infection in the eye, the microsporidia are thought to initially infect the gastrointestinal (GI) tract through ingestion of the infective spores; infections in other body sites are thought to disseminate from the GI tract.

**Select the most sensitive recovery method for *Acanthamoeba* spp. from lens care solutions or corneal biopsies.** A. The trichrome staining method B. The use of monoclonal reagents for the detection of antibody C. The use of non-nutrient agar cultures seeded with Escherichia coli D. The Giemsa stain method

C. The use of non-nutrient agar cultures seeded with Escherichia coli Currently, the most sensitive method of those listed for the recovery of Acanthamoeba spp. from clinical specimens is the non-nutrient agar culture plate seeded with E. coli. The amoebae feed on the bacteria; both trophozoites and cysts can be recovered from the agar surface.

**The microsporidia are organisms (now classified with the fungi) that have been implicated in human disease primarily in:** A. Immunocompromised patients B. Pediatric patients under age 5 years C. Adult patients with congenital immunodeficiencies D. Patients who have been traveling in the tropics

A. Immunocompromised patients ##Footnote Although the microsporidia have been known as pathogens in many groups of animals, their involvement in humans has primarily been in immunocompromised patients, especially those with AIDS. Microsporidia can be found in different tissues, and currently there are a number of genera implicated in human disease.

**When staining *Cystoisospora belli* oocysts with modified acid-fast stains, the important difference between these methods and the acid-fast stains used for acid-fast bacilli (AFB) is:** A. The staining time is much longer with regular AFB acid-fast stains. B. The decolorizer is much weaker than acid alcohol used for AFB decolorizing. C. A counterstain must be used for the modified methods. D. The stain is more concentrated when staining for AFB.

B. The decolorizer is much weaker than acid alcohol used for AFB decolorizing.

**The incorrect match between symptoms and disease is:** A. Dysentery and amebiasis B. Malabsorption symdrome and giardiasis C. Cardiac involvement and chronic Chagas’ disease D. Myalgias and trichuriasis

D. Myalgias and trichuriasis ##Footnote *T. trichiura* (whip worm) may cause diarrhea and occasionally dysentery in very heavy infections; however, the worms are confined to the intestine, and myalgias are not seen in this helminth infection.

**The *incorrect* match between organism and characteristic is:** A. *Chilomastix mesnili* and Shepherd’s crook and lemon shape B. *Plasmodium malariae* and “band trophozoite” C. *Hymenolepis nana* and *striated shell* D. *Wuchereria bancrofti* and sheathed micofilariae

C. *Hymenolepis nana* and *striated shell*

**The *incorrect* match between method and method objective is:** A. Direct wet examination and detection of organism motility B. Knott concentration and the recovery of operculated helminth eggs C. Baermann concentration and the recovery of *Strongyloides* D. Permanent stained fecal smear and confirmation of protozoa

B. Knott concentration and the recovery of operculated helminth eggs

**The *incorrect* match between organism and characteristic/ diagnostic method is:** A. *Dientamoeba fragilis* and tetrad karyosome in the nucleus B. *Toxoplasma gondii* and diagnostic serology C. *Echinococcus granulosus* and daughter cysts D. *Schistosoma mansoni* and egg with terminal spine

D. *Schistosoma mansoni* and egg with terminal spine ##Footnote The egg of *S.mansoni* is characterized by a large lateral spine; *S. haematobium* has the characteristic terminal spine.

**There are few procedures considered STAT in parasitology. The most obvious situation would be:** A. Ova and parasite examination for giardiasis B. Baermann concentration for strongyloidiasis C. Blood films for malaria D. Culture of amebic keratitis

C. Blood films for malaria #Footnote The request for blood films for malaria should always be considered a STAT request. Any laboratory providing these services should have coverage 24 hours a day, 7 days a week. In cases of *P. falciparum malaria, any delay in diagnosing the infection could be fatal for the patient.

**An immunosuppressed man has several episodes of pneumonia, intestinal pain, sepsis with gram-negative rods, and a history of military service in Southeast Asia 20 years earlier. The most likely cause is infection with:** A. *Trypanosoma cruzi* B. *Strongyloides stercoralis* C. *Naegleria fowleri* D. *Paragonimus westermani*

B. *Strongyloides stercoralis* ##Footnote A latent infection with *S. stercoralis* acquired years before may cause severe symptoms in the immunosuppressed patient (“autoinfective” capability of life cycle and migratory route through the body leading to the hyperinfection syndrome and disseminated disease).

**In a pediatric patient, the recommended clinical specimens for recovery of *Enterobius vermicularis* are the:** A. Stool specimens B. Sigmoidoscopy scraping C. Duodenal aspirates D. Series of cellophane tape preparations

D. Series of cellophane tape preparations

**Eosinophilic meningoencephalitis is a form of larva migrans, causing fever, headache, stiff neck, and increased cells in the spinal fluid. It is caused by:** A. *Necator americanus* B. *Angiostrongylus cantonensis* C. *Ancylostoma braziliense* D. *Stronglyloides stercoralis*

B. *Angiostrongylus cantonensis* ##Footnote Esosinophilic meningoencephalitis is a form of larva migrans and id caused by *A. cantonesis*, the rat lungworm. This infection, common in the Pacific region, is associated with CSF symptoms and sometimes eye involvement.

**”Cultures of parasites are different from bacterial cultures; no quality control is needed.” This statement is:** A. True, if two tubes of media are set up for each patient B. True, if the media are checked every 24 hours C. False, unless two different types of media are used D. False, and organism and media controls need to be set up

D. False, and organism and media controls need to be set up

**Protozoan cysts were seen in a concentration sediment and tentatively identified as *Entamoeba coli.* However, the organisms were barely visible on the permanent stained smear because:** A. The organisms were actually not present in the concentration sediment B. There were too few cysts to allow identification on the stained smear C. *Entamoeba coli* cysts were present but poorly fixed due to the thick cyst wall D. The concentrate and permanent stained smear were not from the same patient

C. *Entamoeba coli* cysts were present but poorly fixed due to the thick cyst wall

**When humans have hydatid disease, the causative agent and host classification are:** A. *Echinococcus granulosus*—accidental intermediate host B. *Echinococcus granulosus*—definitive host C. *Taenia solium*—accidental intermediate host D. *Taenia solium*—definitive host

A. *Echinococcus granulosus*—accidental intermediate host ##footnote

**A 45-year-old hunter developed fever, myalgia, and periorbital edema. He has a history of bear meat consumption. The most likely causative agent is:** A. *Toxoplasma gondii* B. *Taenia solium* C. *Hymenolepis nana* D. *Trichinella spiralis*

D. *Trichinella spiralis*

**In a condition resulting from the accidental ingestion of eggs, the human becomes the intermediate host, rather than the definitive host. The correct answer is:** A. Trichinosis B. Cysticercosis C. Ascariasis D. Strongyloidiasis

B. Cysticercosis

**A transplant recipient on immunosuppressive drugs developed increasing diarrhea. The most likely combination of disease and diagnostic procedure is:** A. Trichinosis and trichrome staining B. Microsporidiosis and modified trichrome staining C. Toxoplasmosis and Gram staining D. Paragonimiasis and wet preparation

B. Microsporidiosis and modified trichrome staining

**After returning from a 2-year stay in India, a patient has eosinophilia, an enlarged left spermatic cord, and bilateral inguinal lymphadenopathy. The most likely clinical specimen and organism match is:** A. Thin blood films and *Leishmania* B. Urine and concentration for *Trichomonas vaginalis* C. Thin blood films and *Babesia* D. Thick blood films and microfilariae

D. Thick blood films and microfilariae

**Patients with severe diarrhea should use “enteric precautions” to prevent nosocomial infections with:** A. *Giardia lamblia (G. intestinalis, G. duodenalis)* B. *Ascaris lumbricoides * C. *Cryptosporidium* spp. D. *Cystoisospora belli*

C. *Cryptosporidium* spp.

**A 60-year-old Brazilian patient with cardiac irregularities and congestive heart failure suddenly dies. Examination of the myocardium revealed numerous amastigotes, and indication that the cause of death was most likely:** A. Leishmaniasis with *Leishmania donovani* B. Leishmaniasis with *Leishmania braziliense* C. Trypanosomiasis with *Trypanosoma gambiense* D. Trypanosomiasis with *Trypanosoma cruzi*

D. Trypanosomiasis with *Trypanosoma cruzi*

**When analysis of blood smears for malaria are requested, what patient information should be obtained?** A. Diet, age, gender B. Age, antimalarial medication, gender C. Travel history, antimalarial medication, date of return to United States D. Fever patterns, travel history, diet

C. Travel history, antimalarial medication, date of return to United States

**In an outbreak of diarrheal disease traced to a municipal water supply, the most likely causative agent is:** A. *Crypotosporidum* spp. B. *Crystoisospora belli* C. *Entamoeba histolytica* D. *Dientamoeba fragilis*

A. *Crypotosporidum* spp.

**Within the United States, sporadic mini-outbreaks of diarrheal disease have been associated with the ingestion of strawberries, raspberries, fresh basil, mesclun (baby lettuce leaves), and snow peas. The most likely causative agent is:** A. *Dientamoeba fragilis* B. *Cyclospora cayetanensis* C. *Schistosoma mansoni* D. *Cystoisospora belli*

B. *Cyclospora cayetanensis*

**Which of the following statements is true regarding onchocerciasis?** A. The adult worm is present in blood B. The microfilariae are in blood during the late evening hours C. The diagnostic test of choice is the skin snip D. The parasite resides in the deep lymphatics

C. The diagnostic test of choice is the skin snip

**The most prevalent helminth to infect humans is:** A. *Enterobius vermicularis*, the pinworm B. *Ascaris lumbricoides*, the large intestinal roundworm C. *Taenia saginata*, the beef tapeworm D. *Schistosoma mansoni*, one of the blood flukes

A. *Enterobius vermicularis*, the pinworm

**A helminth egg is described as having terminal polar plugs. The most likely helminth is:** A. Hookworm B. Trichuris trichiura C. Fasciola hepatica D. Diphyllobothrium latum

B. Trichuris trichiura

**Ingestion of which of the following eggs will result in infection?** A. *Strongyloides stercoralis* B. *Schistosoma japonicum* C. *Toxocara canis* D. *Opisthorchis sinensis*

C. *Toxocara canis*

** *Plasmodium vivax* and *Plasmodium ovale* are similar because they:** A. Exhibit Schuffner dots and have a true relapse in the life cycle B. Have no malarial pigment and multiple rings C. Commonly have appliqué forms in the red cells D. Have true stippling, do not have a relapse stage, and infect old red cells

A. Exhibit Schuffner dots and have a true relapse in the life cycle

**The term *internal autoinfection* can be associated with the following parasites:** A. *Crytosporidium* spp. and *Giardia lamblia (G. intestinalis, G. duodenalis)* B. *Cystoisospora belli* and *Strongyloides stercoralis* C. *Cryptosporidium* spp. and *Strongyloides stercoralis* D. *Giardia lamblia (G. intestinalis, G. duodenalis)* and *Cystoisospora belli*

C. *Cryptosporidium* spp. and *Strongyloides stercoralis*

**Microsporidia have been identified as causing severe diarrhea, disseminated disease in other body sites, and ocular infections. Routes of infection have been identified as:** A. Ingestion B. Inhalation C. Direct contamination from the environment D. Ingestion, inhalation, and direct contamination from the environment

D. Ingestion, inhalation, and direct contamination from the environment

**An immunocompromised patient continues to have diarrhea after repeated ova and parasites (O&P) examinations (sedimentation concentration, trichrome permanent stained smear) were reported as negative; organisms that might be responsible for the diarrhea include:** A. *Cryptosporidium* spp., *Giardia lamblia (G. intestinalis, G. duodenalis),* and *Cystoisospora* B. *Giardia lamblia (G. intestinalis, G. duodenalis*), microsporidia, and *Endolimax nana* C. *Taenia solium* and *Endolimax nana* D. *Cryptosporidium* spp. and microsporidia

D. *Cryptosporidium* spp. and microsporidia

**Confirmation of a infection with microsporidia can be achieved by seeing:** A. The oocyst wall B. Sporozoites within the oocyst C. Evidence of the polar tubule D. Organisms stained with modified acid-fast stains

C. Evidence of the polar tubule

**Early ring forms of the fifth human malaria, *Plasmodium knowlesi*, resemble those of:** A. *Plasmodium vivax* B. *Plasmodium ovale* C. *Plasmodium malariae* D. *Plasmodium falciparum*

D. *Plasmodium falciparum*

**Parasite stages that are immediately infective for humans on passage from the gastrointestinal tract include:** A. *Schistosoma* spp. eggs B. *Toxoplasma gondii* bradyzoites C. *Ascaris lumbricoides* eggs D. *Cryptosporidium* spp. oocysts

D. *Cryptosporidium* spp. oocysts

**Older developing stages (trophozoites, schizonts) of the fifth human malaria, *Plasmodium knowlesi*, resemble those of:** A. *Plasmodium vivax* B. *Plasmodium ovale* C. *Plasmodium malariae* D. *Plasmodium falciparum*

C. *Plasmodium malariae* ##Footnote Older developing stages (developing trophozoites, schizonts) of the fifth human malaria, P.knowlesi, tend to closely resemble those of *P. malariae* (band forms, “daisy head” mature schizont).

**Autofluorescence requires no stain and is recommended for the presumptive identification of:** A. *Entamoeba histolytica* cysts B. *Toxoplasma gondii* tachyzoites C. *Dientamoeba fragilis* trophozoites D. *Cyclospora cayetanesis* oocysts

D. *Cyclospora cayetanesis* oocysts

**Key characteristics of infection with *Plasmodium knowlesi* include:** A. Rapid erythrocyte cycle (24 hours), will infect all ages of RBCs, and can cause serious disease B. Erythrocytic cycle limited to young RBCs and causes a relatively benign disease C. The possibility of a true relapse from the liver, infection in older RBCs, and causes serious disease D. Extended life cycle (72 hours), will infect all ages of RBCs, and disease is similar to that caused by Plasmodium ovale.

A. Rapid erythrocyte cycle (24 hours), will infect all ages of RBCs, and can cause serious disease

**Microsporidial infections can be confirmed by using:** A. Light microscopy and modified trichrome staining B. Phase contrast microscopy and routine trichrome staining C. Electron microscopy and modified acid-fast staining D. Fluorescence microscopy and hematoxylin staining

A. Light microscopy and modified trichrome staining

**Although the pathogenicity of *Blastocystis* spp. remains controversial, newer information suggests that:** A. Most organisms are misdiagnosed as artifacts B. Approximately 10 subtypes/strains are included in the name, some of which are pathogenic and some are nonpathogenic C. The immune status of the host is solely responsible for symptomatic infections D. The number of organisms present determines pathogenicity

B. Approximately 10 subtypes/strains are included in the name, some of which are pathogenic and some are nonpathogenic

**Potential problems using EDTA anticoagulant and holding the blood too long prior to preparation of thick and thin blood films include:** A. Changes in parasite morphology, loss of organisms within several hours, and poor staining B. Loss of Schuffner dots, poor adherence of blood too the glass slide, and parasites C. None of the above D. All of the above

D. All of the above

**Key characteristics of the thick film include:** A. The ability to see the parasite within the RBCs B. The ability to identify the parasites to the species level C. The examination of less blood than the thin blood film D. The necessity to lake the RBCs during or prior to staining

D. The necessity to lake the RBCs during or prior to staining