Parasitology 2

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Angela6
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198459
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Parasitology 2
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2013-02-06 22:40:57
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Parasitology review class
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  1. What are some substances that will interfere with the examination of feces for ova and parasites?
    Antibiotics, antiseptics, burns, laxatives, mineral oil, soap, water, and urine
  2. How many specimens are usually examined for ova and parasites?
    At least 3 since some parasites are eliminated intermittently. 6 specimens are recommended if amebiasis is suspected.
  3. Name several preservatives for fecal specimens for O &P.
    10% formalin, Polyvinyl alcohol, (SAF) sodium acetate formalin, (MIF) merthiolate iodine formalin
  4. What is the disadvantage of mercuric chloride-based polyvinyl alcohol?
    It contains mercury, it's poisonous and requires special handling and disposal
  5. What guidline should be followed regarding the number and timing of stool specimens for routine O & P testing?
    No more than 2/3 specimens per patient should be submitted and specimens should not be submitted from inpatients after the fourth day of hospitalization.
  6. Recommended time limits for examination of formed, soft, and liquid stool specimens for O & P.
    • Liquid: within 30 min
    • Soft: within 1 hour
    • Formed: within 24 hours
  7. What 3 exams are usually performed on fresh stool specimen submitted for O & P examination?
    Direct wet preparation, a concentration, permanent stained smear.
  8. What is the purpose of the saline direct smear in the ova and parasite examination?
    Study the motility of trophozoites. If there is a significant delay between collection of the specimen and receipt in the lab.
  9. What is the consistency of the stool specimen in which trophozoites are most likely to be found?
    Liquid specimen. Troph are present in stool specimens when there is rapid evacuation of the bowel.
  10. How concentrated should the saline direct smear be in the ova and parasite exam?
    Be able to read newsprint through it
  11. Why is iodine used in the direct smear in the ova and parasite exam?
    Iodine stains the cysts and allows visualization of the nuclear structure. Trophs are killed by iodine, so a saline direct smear should be exam first.
  12. What kind of iodine is used in the direct smear exam in the O & P procedure?
    • Dobell and O'Connor's
    • D'Antoni's
    • Lugol's
    • Gram stain is too concentrated
  13. What is the purpose of the concentration technique in the O & P procedure?
    Concentrates the parasites and separates them from the fecal debris so they are easier to find.
  14. Which concentration technique is most widely used for O & P?
    Sedimentation method. Easiest method and least subject to technical error.
  15. What is the disadvantage of the formalin-ether sedimentation method?
    Ether must be stored in an explosion-proof refrigerator.
  16. What reagent is used for the floation concentration method?
    33% zinc sulfate (SG 1.180)
  17. What is the advantage of the zinc sulfate flotation method?
    Results in a cleaner prep than the sedimentation method
  18. What is the disadvantage of the zinc sulfate flotation method?
    • Operculated eggs
    • Unfertilized Ascaris eggs may be missed
  19. Which form of protozoa is not recovered by a concentration?
    Trophozoites
  20. Which parasites are best diagnosed by a permanent stained smear?
    • Protozoa
    • Permanent stained smear should be performed on all stools because interstinal protozoa may be missed in the concentration examination.
  21. Name a fixative used for preparation of a permanent smear.
    • Schaudinn's.
    • Specimen is smeared on a slide and while still wet, dipped in the fixative for 30 mins
  22. Name two stains used for permanent stained slides in parasitology.
    • Iron hematoxylin
    • Trichrome
  23. What is the Enterotest (string test)?
    • Method for recovering Giardia and Strongyloides from the duodenum when stool exams are negative. Gelatin capsule containing nylon string is used. Part of the string protrudes from the capsule and is taped to the patient's face. Patient is instructed to swallow the capsule.
    • After 4 hours the string is retrieved and the mucus clinging to the string is examined.
  24. How can one determine the size of a parasite observed under the microscope?
    Calibrated micrometer  placed in one ocular of the microscope.
  25. How is the ocular micrometer calibrated?
    Exact distance between markings is determined by comparison with a stage micrometer with known calibration markings. An appropriate lens factor is determined for each objective. Ocular micrometers must be calibrated for the microscopes which are used.
  26. Which intestinal ameba is pathogenic for man?
    Entamoeba histolytica
  27. Name an ameba with cigar shaped chromatoidal bodies in the cyst.
    E. histolytica
  28. Name an ameba whose trophozoite ingests RBCs.
    E.histolytica
  29. Name an ameba whose nucleus has delicate, even, peripheral chromatin and a delicate, central karyosome.
    E. histolytica
  30. Name an ameba whose cyst contains up to 8 nuclei.
    E. coli
  31. Name an ameba whose cyst has a large glycogen vacuole.
    Iodamoeba butschlii
  32. Name an ameba whose cyst has only one nucleus.
    Iodamoeba butschlii
  33. Which ameba causes granulomatous amebic encephalitis (GAE) and ulcerative keratitis in contact lens wearers?
    • Acanthamoeba.
    • Contracted by swimming in contaminated water or by inadequate cleaning of contact lens.
    • Diagnosis: exam of the brain
  34. Which ameba causes primary amebic meningoencephalitis (PAM)
    • Naegleria fowleri.
    • Contracted by swimming in contaminated water. Trophs may be found in the CSF.
  35. Name a flagellate that does not have a cyst.
    • Trichomonas
    • Dientamoeba
  36. Name a flagellate that has a lemon shaped cyst.
    Chilomastix mesnili
  37. Name a flagellate whose trophs always has two nuclei
    Giardia lamblia
  38. Name a flagellate that can be seen in a blood smear.
    • Trypanosoma.
    • Cause sleeping sickness and Chagas disease
  39. Name a flagellate that can be seen in urethral discharge.
    • Trichomonas vaginalis.
    • Spread by sexual contact.
  40. Name a flagellate which resembles an ameba because its flagella can only be seen with electron microscope.
    Dientamoeba fragilis
  41. Name a common intestinal protozoan whose troph usually has 2 nuclei and which does not have a cyst stage.
    Dientamoeba fragilis
  42. Name a flagellate whose cyst has two or four nuclei at the anterior end, parabasal bodies, an axostyle, and cytoplasm that shrinks away from the cell wall.
    Giardia lamblia
  43. Name a flagellate that looks like an old man with glasses.
    Giardia Lamblia
  44. Name the most common intestinal protozoan infection in the US
    Giardia lamblia
  45. Name a flagellate that can be diagnosed from duodenal aspirates or the Enterotest capsule
    Giardia
  46. Name a protozoan that is ciliated and has a large kidney shaped macronucleus and a small micronucleus
    Balantidium coli
  47. Which is the largest protozoan to infect man?
    Balantidium coli
  48. Which parasites can be found in the blood?
    Plasmodium, Babesia, Trypanosoma, and microfilariae
  49. Name two parasites that live inside erythrocytes.
    Plasmodium and Babesia
  50. Name a protozoan that infects reticuloendothelial cells.
    • Leishmania
    • Cause kala azar and cutaneous and mucocutaneous leishmaniasis
  51. Name the parasite that causes sleeping sickness.
    • Trypanosoma gambiense
    • T. rhodesiense
  52. What causes Chagas disease?
    Trypanosoma cruzi
  53. Which sporozoan causes maliaria?
    Plasmodium
  54. Which parasite has killed more people worldwide than any other?
    Plasmodium
  55. Name a parasite that requires the Anophles mosquito for its sexual cycle.
    Plasmodium
  56. Which species of Plasmodium is associated with enlarged RBC?
    P. vivax and P. ovale
  57. Which species of Plasmodium has sausage-shaped or cresent-shaped gametocytes?
    P. falciparum
  58. Which species of Plasmodium commonly has multiple ring forms within on RBC?
    P. falciparum
  59. Which species of Plasmodium is most malignant?
    P. falciparum
  60. With which species of Plasmodium does one see rings and gametocytes only?
    P. falciparum
  61. Which species of Plasmodium is characterized by band-shaped troph?
    P. malariae
  62. With which species of Plasmodium does one see Schuffner's dots?
    P.vivax and P.ovale
  63. When is the best time to draw blood for malaria smears?
    Shortly after a paroxysm (shaking chills and fever). Blood should be taken at 6-8 hour intervals so different stages of the parasite can be studied to identify the species.
  64. How is thick malaria smear prepared?
    • 3 drops of blood are placed on a slide, allowed to dry, and placed directly into Giemsa stain without fixation.
    • Concentrates the parasites and removes hemoglobin from the RBCs so that the parasites are easier to see.
    • Only used for screening because the parasites are distorted and the species cannot be determined.
  65. Name a protozoan that can be found in municipal water supplies, causes a profuse watery diarrhea, is a serious risk to immunocompromised patients, and appears as red spherical structures approx. 6 microns in diameter on a modified AFS.
    Cryptosporidium
  66. Name a protozoan that is round to ovoid, 6-40 u in diameter, with a large central body and peripheral granules.
    • Blastocystis hominis.
    • Organism used to be considered a nonpathogenic yeast. It is now considered a protozoan and is thought to be an intestinal pathogen when present in large numbers in the stool.
  67. Which protozoan can be spread by infective oocysts in cat feces?
    Toxoplasma gondii
  68. Which protozoan can cause neurologic problems if contracted by the fetus after the first trimester?
    Toxoplasma gondii
  69. Which protozoan is the major cause of encephalitis in AIDs patients?
    Toxoplasma gondii
  70. How is toxoplasmosis diagnosed?
    Serologic tests
  71. Name a roundworm that has a barrel shaped egg with a clear plug at either end.
    Trichuris trichiura, whipworm
  72. What is the most common helminth infection in the US?
    Pinworm. Enterobius vermicularis
  73. Name a roundworm that is diagnosed by the scotch tape prep.
    Enterobius vermicularis, pinworm
  74. When is the best time to collect a scotch tape prep?
    First thing in the morning, before bathing or defecation.
  75. Name a roundworm whose egg resembles a loaf of Italian bread-flat on one side and rounded on the other.
    Enterobius vermicularis
  76. Name a nematode whose diagnostic stage is the rhabditiform larva.
    Strongyloides
  77. Name the most common helminth infection in the world.
    Ascaris lumbricoides
  78. Name the roundworm that looks like an earthworm.
    Ascaris lumbricoides
  79. Name a roundworm that can pass from the anus, nose, or mouth.
    Ascaris lumbricoides
  80. Which intestinal parasite is not diagnosed by an O & P prep?
    Pinworm. Diagnosed by scotch tape prep
  81. Which intestinal roundworm infection is contracted by skin penetration by the filariform larva or sexually, includes larval migration through the lungs, and can be fatal in an immunocompromised host?
    Strongyloides stercoralis
  82. Name an intestinal roundworm in which diagnostic stage is not the ovum.
    • Strongyloides stercoralis
    • Diagnostic stage is rhabditiform larva
  83. Name two hookworms.
    • Necator americanus (American hookworm)
    • Ancylostoma duodenale (Old world hookworm)
  84. How are hookworm infections contracted?
    • Skin penetration by the filariform larva
    • Larva may also be ingested
  85. Which intestinal roundworms can lead to anemia?
    • Hookworms
    • Necator and Ancylostoma
  86. Which parasitic infections cause marked eosinophilia?
    Those that have a migratory cycle through the lungs, such as Necator, Strongyloides, Ascaris
  87. Which nematode is contracted from undercooked pork and is found in encysted in the host's skeletal muscle?
    Trichinella spiralis
  88. Name the beef tapeworm.
    Taenia saginata
  89. Name the pork tapeworm.
    Taenia solium
  90. Name the fish tapeworm.
    Diphyllobothrium latum
  91. How are Taenia saginata and Taenia solium differentiated?
    • By the scolex or the number of lateral uterine branches.
    • T. solium, has hooklets around the rostellum, 7-13 uterine branches per side with regularly alternating genital pores.
    • T. saginata, 15-30 uterine branches per side with irregularly alternating genital pores.
  92. Describe Taenia eggs
    • Spherical, approximately 35 microns
    • Yellow-brown, have thick radially-striated shell.
  93. Name the tapeworm that causes cysticercosis.
    Taenia solium, contracted by ingestion of eggs. Man serves as the intermediate host and larvae can migrate to any organs.
  94. What is the most common tapeworm in the US?
    • Hymenolepsis nana (dwarf tapeworm)
    • Does not require intermediate host
    • Causes growth retardation in children and autoinfective.
  95. Which tapeworm has an almond-shaped scolex with lateral grooves on each side and central rosette- shaped uterus?
    Diphyllobothrium latum
  96. Which tapeworm has an operculated ovum?
    Diphyllobothrium latum
  97. Name the tapeworm that causes hydatid disease.
    • Echinococcus granulosis
    • Man is an accidental host
    • Following ingestion of fecal material from an infected dog.
    • Diagnosis is from ID of scoleces in needle biopsy material from the cyst
  98. Which tapeworm can cause a Vitamin B12 deficiency?
    Diphyllobothrium latum
  99. Which group of parasites requires a snail in its life cycle?
    Flukes (trematodes)
  100. Which fluke is one of the most frequent infections seen in Asian refugees?
    • Clonorchis sinensis.
    • Ovum of C. sinensis one of smallest passed by man.
    • Bulb shaped with opercular shoulders and small comma shaped protuberance at the posterior end.
  101. Name the only parasite that lives in the excretory system and whose eggs can be found in urine sediment.
    Schistosoma haematobium.
  102. Name a fluke whose egg can be found in sputum?
    • Paragonimus westermani
    • Ovum resembles a Chinese vase
  103. Which trematode has an elongated ovum, approximately 155 microns by 65 microns, with a pronounced lateral spine?
    Schistosoma mansoni
  104. Which is the largest trematode to infect man?
    Fasciolopsis buski
  105. Which parasite ova could be infectious to the lab tech?
    • Enterobius
    • Taenia solium
    • Hymenolepsis nana
  106. Describe Charcot-Leyden crystals and explain their significance
    Slender crystals with pointed ends which vary in size and stain red-purple with the trichome stain. Represent breakdown products of eosinophils and are sometimes seen with the parasitic infections.

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