Ciulla: Parasitology

1. Enterobius vermicularis infection is usually diagnosed by finding

A. Eggs in perianal specimens

B. Larvae in perianal specimens

C. Larvae in feces

D. Eggs in the feces

A. Eggs in perianal specimens

2. The best direct diagnosis of Echinococcus granulosus infection in humans is made by identification of

A. Adult worms in the intestine

B. Adult worms in tissues

C. Eggs in feces

D. Hydatid cysts in tissues

D. Hydatid cysts in tissues

3. Which statement is correct for specimen collection and processing?

A. Stool samples can contain urine.

B. Stools can be frozen without affecting

parasitic structure.

C. Liquid stools are best for detecting

ameba and flagellate trophozoites.

D. Unpreserved stools can remain at

room temperature for up to 72 hours.

C. Liquid stools are best for detecting

ameba and flagellate trophozoites.

4. Cysts are the infective stage of this intestinal flagellate.

A. Balantidium coli

B. Dientamoeba fragilis

C. Entamoeba coli

D. Giardia lamblia

D. Giardia lamblia

5. Eggs or larvae recovered in the stool are not routinely used to diagnose infections caused by which one of the following helminths?

A. Trichinella spiralis

B. Strongyloides stercomlis

C. Necator americanus

D. Ascaris lumbricoides

A. Trichinella spiralis

6. Many parasites have different stages of growth within different hosts. The host where the sexual reproductive stage of the parasites exists is called the

A. Commensal

B. Definitive host

C. Intermediate host

D. Vector

B. Definitive host

7. Species identification of an immature amebic cyst can be very difficult. The presence of a large glycogen mass is sometimes seen in

A. Dientamoeba fragilis

B. Endolimax nana

C. Entamoeba coli

D. Entamoeba histolytica

C. Entamoeba coli

8. Which of the following is typical in cysts of lodamoeba biitschlii?

A. A glycogen mass

B. Blunt chromatoidal bars

C. Four nuclei with large karyosomes

D. Many ingested bacteria

A. A glycogen mass

9. Which of the following is the most important feature in differentiating cysts of Entamoeba histolytica from E. dispar?

A. Number of nuclei

B. Size of the cyst

C. Shape of the karyosome

D. Distinguishing surface antigens by

immunologic assays

D. Distinguishing surface antigens by

immunologic assays

10. Which of the following findings in a peripheral blood smear is especially associated with tissue-invading helminths but may also be found in a variety of allergic conditions and other diseases?

A . Eosinophilia

B. Leukopenia

C. Lymphocytosis

D. Neutropenia

A . Eosinophilia

11. A 48-year-old man from Texas developed fever and weakness 16 days after a hunting trip in northwest Tanzania. Several days after the onset of fever, he noticed a raised, tender, erythematous nodule (6-8 cm in diameter) on the posterior aspect of his right arm. He was hospitalized in Africa and treated for

5 days with a cephalosporin for presumed cellulitis. After little improvement, he returned to Texas. On arrival, the patient had a temperature of 38.9°C (102°F), a morbilliform rash of the trunk, and right- sided, anterior cervical lymphadenopathy. Cerebrospinal fluid contained 12 red cells and 18 mononuclear cells/uL and a normal protein level (32 mg/dL). Laboratory tests of peripheral blood revealed a hemoglobin level of 107 g/L, a white cell count of

2.4 X 109/L, and a platelet count of

75 X 109/L. The diagnosis was made by finding the extracellular flagellate parasite in a peripheral blood smear. Which of the following is the most probable etiologic agent of this infection?

A. Leishmania donovani

B. Trypanosoma brucei

C. Tiypanosoma cruzi

D. Toxoplasma gondii

B. Trypanosoma brucei

12. Which species of malaria parasite usually

has ameboid trophozoites and produces small reddish dots in the red blood cell cytoplasm?

A. Plasmodium knowlesi

B. Plasmodium falciparum

C. Plasmodium malariae

D. Plasmodium vivax

D. Plasmodium vivax

13. With a fecal specimen, which one of the following is the most dependable procedure for the accurate, specific diagnosis of an intestinal amebic infection?

A. Direct saline wet mount

B. Direct iodine wet mount

C. Permanently stained smear

D. Formalin-ethyl acetate sedimentation

technique

C. Permanently stained smear

14. In an examination of stained blood films, Babesia spp. are likely to resemble

A. Leishmania donovani

B. Plasmodium falciparum

C. Toxoplasma gondii

D. Trypanosoma cruzi

B. Plasmodium falciparum

15. Which of the following is a mercury- containing fixative used to preserve parasites in stool specimens?

A. Formalin

B. Sodium acetate

C. Buffered glycerol

D. Polyvinyl alcohol

D. Polyvinyl alcohol

16. Examination of a fecal smear following acid-fast stain reveals round acid-fast positive structures 8-10 um in diameter. You should suspect

A. Cryptosporidium

B. Cyclosporum

C. Isospora

D. Microsporidia

B. Cyclosporum

17. A 22-year-old male presents to his family physician complaining of fatigue, muscle pain, periorbital edema, and fever. He denies travel outside the U.S. The physician suspects infectious mononucle- osis; however, serologic tests for infec- tious mononucleosis are negative. The complete blood count revealed a slightly elevated white blood count, and there were

10% eosinophils on the differential. Which of the following should be considered part of the differential diagnosis?

A. Ascaris lumbricoides

B. Taenia solium

C. Trichinella spiralis

D. Trypanosoma cruzi

C. Trichinella spiralis

18. Which Schistosoma species has a large terminal spine?

A. S. haematobium

B. S.japonicum

C. S. mansoni

D. S. mekongi

A. S. haematobium

19. Elephantiasis is a complication associated with which of the following?

A. Cysticercosis

B. Guineaworm

C. Hydatid cyst disease

D. Filariae

D. Filariae

20. A patient with history of human immuno- deficiency virus infection presents with a 5-day history of diarrhea and weight loss. A series of stool specimens is collected and examined for the presence of ova and parasites. An acid-fast stain on direct smear reveals pink-stained round structures approximately 4 (amin diameter. The most likely pathogen is

A. Blastocystis hominis

B. Cryptosporidium sp.

C. Isospora sp.

D. Microsporidium

B. Cryptosporidium sp.

21. A 55-year-old female presents to her physician complaining of a fever that "comes and goes" and fatigue. A complete blood count reveals decreased red blood cell count and hemoglobin. History reveals the patient recently traveled through Europe and Africa. You should suspect

A. Cutaneous larval migrans

B. Filariasis

C. Malaria

D. Trichinella

C. Malaria

22. The disease most commonly associated with Acanthamoeba sp. is

A. Diarrhea

B. Keratitis

C. Liver abscess

D. Meningoencephalitis

B. Keratitis

23. A modified trichrome stain of a fecal smear can be used to detect microsporidia. Which of the following would describe the appearance of this parasite in this stain?

A. Purple circles, 10-15 um in diameter

B. Pink ovals, 1-3 um in diameter

C. Blue ovals, 4-6 urn in diameter

D. Fluorescent circles, 8-12 um in

diameter

B. Pink ovals, 1-3 um in diameter

24. Hydatid cysts in humans are due to ingestion of a tapeworm stage normally found in canines. This stage is the

A. Cercaria

B. Cercocystis

C. Cysticercus

D. Embryonated egg

D. Embryonated egg

25. Oocysts, the infective stage of Toxoplasma gondii, is found in

A. Cat feces

B. Humanfeces

C. Undercooked pork

D. Undercooked beef

A. Cat feces

26. A 15-um pear-shaped flagellate with a visible parabasal body and "falling leaf" motility in a direct saline mount of a diarrheal stool specimen is most probably

A. Balantidium coli

B. Chilomastix mesnili

C. Giardia lamblia

D. Trichomonas hominis

C. Giardia lamblia

27. This parasitic infection may result in vitamin B12 deficiency,andindividuals with pernicious anemia are predisposed to more severe symptoms.

A. Diphyllobothrium latum

B. Echinococcus granidosus

C. Hymenolepis diminuta

D. Taenia saginata

A. Diphyllobothrium latum

28. Knowledge of nocturnal periodicity is especially important in the diagnosis of certain infections caused by

A. Babesia

B. Plasmodium

C. Microfilariae

D. Trypanosoma

C. Microfilariae

29. For which of the following diseases is close contact with an infected human host the most important mechanism of transmission?

A. Schistosomiasis

B. Toxoplasmosis

C. Trichinosis

D. Trichomoniasis

D. Trichomoniasis

30. Which of the following helminths produces an elongate, barrel-shaped egg (50 X 22 |xm) with a colorless polar plug at each end?

A. Ascaris lumbricoides

B. Hymenolepis nana

C. Necator americanus

D. Trichuris trichiura

D. Trichuris trichiura

31. Which species of Plasmodium may readily be identified when crescent-shaped gametocytes are found in stained blood films?

A. P. falciparum

B. P.malariae

C. P.ovale

D. P.vivax

A. P. falciparum

32. Cysts of Giardia lamblia

A. Contain four nuclei

B. Are motile by flagella

C. Have an undulating membrane

D. Are rarely found in stool specimens

A. Contain four nuclei

33. Migration of larva through the skin can sometimes produce allergic reactions called larva migrans; this is associated with

A. Strongyloides stercoralis

B. Dracunculus medinensis C. Onchocerca volvulus

D. Loa loa

A. Strongyloides stercoralis

34. A free-living ameba that causes primary amebic meningoencephalitis is

A. Dientamoebafragilis

B. Entamoeba coli

C. Entamoeba histolytica

D. Naegleria fowleri

D. Naegleria fowleri

35. Decontamination of drinking water, fruits, and vegetables before consumption is necessary in countries without well- developed public sanitation. Which of the following diseases would probably be least affected by that kind of precaution?

A. Amebiasis

B. Ascariasis

C. Filariasis

D. Giardiasis

C. Filariasis

36. Which stage of Taenia saginata is usually infective for humans?

A. Cysticercus larva

B. Embryonated egg

C. Filariform larva

D. Rhabditiform larva

A. Cysticercus larva

37. This amebic cyst has an average size of 6-8 um and is usually spherical. When mature, it has four nuclei, but immature cysts with one or two nuclei are often seen.Thenucleihavefineuniform granules of peripheral chromatin and small,discrete,usuallycentral karyosomes. Chromatoidal bars with bluntly rounded ends are sometimes present. Name the species.

A. Endolimax nana

B. Entamoeba coli

C. Entamoeba hartmanni

D. Entamoeba histolytica

C. Entamoeba hartmanni

38. Which stage of Trichuris trichiura is infective for humans?

A. Proglottid

B. Filariformlarva

C. Rhabditiformlarva

D. Embryonated ovum

D. Embryonated ovum

39. An intestinal parasite is seen in an iodine- stained fecal wet mount that is described as being 25 (Jimin diameter with a homogenously stained central body surrounded by a thin ring of cytoplasm containing a number of nuclei. This best describes

A. Blastocystis hominis

B. Endolimax nana

C. Entamoeba dispar

D. lodamoeba btitschlii

A. Blastocystis hominis

40. Sanitary disposal of human feces is the most important factor in decreasing the incidence of most infections caused by intestinal parasites. Which of the following diseases would not be affected by that kind of sanitation?

A. Ascariasis

B. Taeniasis

C. Trichinosis

D. Hookworminfection

C. Trichinosis

41. Which species of Plasmodium is charac- terized by the presence of Schiiffner's dots in the infected erythrocytes?

A. Plasmodiumfalciparum

B. Plasmodium knowlesi

C. Plasmodium malariae

D. Plasmodium ovale

D. Plasmodium ovale

42. Which of the following is the largest intestinal protozoa infecting humans?

A. Balantidium coli

B. Dientamoeba fragilis

C. Entamoeba histolytica

D. Giardia lamblia

A. Balantidium coli

43. The rhabditiform larvae of Strongyloides stercoralis

A. Mate and produce ova

B. Areinfectiveforhumans

C. Are the diagnostic form found in feces

D. Are found in the blood of infected

humans

C. Are the diagnostic form found in feces

44. Which species of Plasmodium can have exoerythrocytic stages capable of causing relapses months or years after initial infection?

A. P. falciparum

B. P. ovale

C. P. malariae

D. P. cynomolgi

B. P. ovale

45. A Giemsa-stained thick blood film showed many ring forms with no older stages, and a number of the rings had double chromatin dots. These findings are characteristic of

A. P. falciparum

B. P. vivax

C. P. malariae

D. P. ovale

A. P. falciparum

46. Which of the following nematode parasites is acquired from eating inadequately cooked, infected pork?

A. Strongyloides stercoralis

B. Taenia saginata

C. Taenia solium

D. Trichinella spiralis

D. Trichinella spiralis

47. Which of the following pairs of helminths cannot be reliably differentiated by the appearance of their eggs?

A. Ascaris lumbricoides and Necator

americanus

B. Hymenolepis nana and H. diminuta

C. Necator americanus and Ancylostoma

duodenale

D. Diphyllobothrium latum and Fasciola

hepatica

C. Necator americanus and Ancylostoma

duodenale

48. Which of the following forms of Toxoplasma gondii are produced in infected humans?

A. Bradyzoites

B. Macrogametes

C. Sporoblasts

D. Oocysts

A. Bradyzoites

49. Hematuria is a typical sign of human infection caused by

A. Trypanosoma cruzi

B. Trichinella spiralis

C. Trichomonas vaginalis

D. Schistosoma haematobium

D. Schistosoma haematobium

50. Which of the following is the vector for

Babesia?

A. Fleas

B. Lice

C. Ticks

D. Mosquitoes

C. Ticks

51. Chagas disease (American trypanosomia- sis) is caused by

A. Tiypanosoma brucei

B. Trypanosoma cruzi

C. Leishmania braziliensis D. Dracunculus medinensis

B. Trypanosoma cruzi

52. Which of the following is the preferred anticoagulant for preparing blood smears for diagnosing malaria?

A. EDTA

B. Heparin

C. Sodiumcitrate

D. Sodium fluoride

A. EDTA

53. Refer to Color Plate 38•. This is a photomicrograph of a trichrome stain

of a fecal smear, magnification400 X. The parasite measures 65 X 45 um. What is the identification of this parasite?

A. Balantidium coli

B. Diphyllobothrium latum C. Giardia lamblia

D. Schistosoma japonicum

A. Balantidium coli

54. Refer to Color Plate 39 •. This is a photomicrograph of an iodine wet prep made from a stool sample; magnification is 400X. The ovum is about 70 X 50 um. What is the identification of the parasite?

A. Hookworm

B. Enterobius vermicularis

C. Trichuris trichiura

D. Ascaris lumbricoides

D. Ascaris lumbricoides

55. Refer to Color Plate 4 0 • . This is a photo- micrograph of an iron hematoxylin stain from a fecal smear. The magnification is

1000X. The parasite is approximately 20um long and 15um wide.What is the identification of this parasite?

A. Chilomastix mesnili trophozoite

B. Giardia lamblia trophozoite

C. Trichomonas hominis trophozoite

D. Trichomonas tenax trophozoite

B. Giardia lamblia trophozoite

56. Refer to Color Plate 41•. This is a photo- micrograph of an iron hematoxylin stain from a fecal smear. The magnification is 1000X. The parasite is approximately

12 um in diameter. What is the identifica- tion of this parasite?

A. Entamoeba histolytica trophozoite

B. Entamoeba hartmanni trophozoite

C. Dientamoeba fragilis trophozoite D. Entamoeba coli trophozoite

C. Dientamoeba fragilis

57. Refer to Color Plate 42 •. This is a photo- micrograph of an iodine wet-mount from a fecal sample. The magnification is 1000X. The parasite is approximately

25 um in diameter. What is the identifica- tion of this parasite?

A. Entamoeba histolytica cyst

B. Entamoeba histolytica trophozoite

C. Entamoeba coli cyst

D. Entamoeba coli trophozoite

C. Entamoeba coli cyst

58. Refer to Color Plate 43*. This is a photo- micrograph of an iodine wet mount from

a fecal sample. The magnification is 400X. The ovum is approximately 70 X 38 um. What is the identification of this parasite?

A. Hookworm

B. Ascaris lumbricoides

C. Diphyllobothrium latum D. Taenia solium

A. Hookworm

59. Refer to Color Plate 4 4 • . This is a photo- micrograph of a trichrome stain from a fecal smear. The magnification is 1000X. The parasite is approximately 15 (urn in diameter. What is the identification of this parasite?

A. Entamoeba hartmanni

B. Dientamoeba fragilis

C. lodamoeba biltschlii

D. Blastocystis hominis

D. Blastocystis hominis

60. Refer to Color Plate 45 B. This is a photo- micrograph of a blood smear stained with Wright's stain. Identify the parasite

.

A. Babesia sp.

B. Plasmodium malariae

C. Plasmodiumfalciparum D. Trypanosoma cruzi

B. Plasmodium malariae