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Parasitology/Virology > Protozoan Parasites > Flashcards

Protozoan Parasites Flashcards

1
Q

Trophozoite v. cyst forms of intestinal protozoa: which cause disease in host and which transmit the infection?

A

Trophozoite - causes disease, replicates, motile

Cyst - infective following ingestion, does not replicate, resists environmental stresses, lack motility

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2
Q

Which of the pathogenic intestinal protozoa inhabit the colon?

A

Entamoeba histolytic

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3
Q

What do Giardia and the Coccidia (Cryptosporidium, Cyclospora, Isospora) have in common?

A

Inhabit small bowel

Cause watery diarrhea, dysentery

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4
Q

How are intestinal protozoa detected?

A

Microscopic examination of stool

Antigen detection assays, nucleic acid probes, PCR based assays in developed countries

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5
Q

What are the two species of Entamoeba and which is pathogenic (invasive)?

A

Entamoeba histolytica (invasive) and Entamoeba dispar (non-invasive)

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6
Q

What is the life cycle of Entamoeba histolytica?

A
  • Mature cyst ingested
  • Excystation to trophozoite form in colon, colonizes
  • Can invade outside lumen
  • Excrete cysts
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7
Q

What is the name for the disorder caused by Entamoeba histolytica?

A

Amebiasis

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8
Q

How can you differentiate Entamoeba histolytica from dispar histologically?

A

Histolytica ingests red blood cells and you can see it in trophozoite form on slide

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9
Q

How does Entamoeba histolytica invade the colonic wall?

A
  • Amoebas adhere to epithelial cells (using Gal/GalNac lectin)
  • Secretes cysteine proteases to degrade the extracellular matrix
  • Form pores (amebapores) in target cells that depolarizes and kills cell
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10
Q

What is the characteristic intestinal lesions caused by amebae?

A

Flask-shaped ulcer

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11
Q

Which of the intestinal parasites presents with blood in the stool?

A

Entamoeba histolytica

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12
Q

What is an amoeboma?

A

Ameba perforate wall of colon and cause large inflammatory mass with fibrous granulation tissue
Resembles a tumor so called amoeboma

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13
Q

How do most people with E. histolytica infection present?

A

Asymptomatic cyst passer

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14
Q

What is a significant complication of E. histolytica infection?

A

Hepatic abscess

Could rupture and spread to lung, pericardium

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15
Q

How is amebiasis diagnosed?

A

Intestinal disease - stool microscopy, stool antigen detection, PCR
Liver abscess - ultrasound, CT, serology, needle aspirate (anchovy paste abscess fluid)

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16
Q

What is the treatment for an asymptomatic cyst carrier of E. histolytica?

A

Luminal agent

  • Diloxanide furoate
  • Paromomycin
  • Iodoquinol
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17
Q

What is the treatment for someone with invasive disease due to E. histolytica?

A

Metronidazole AND a luminal agent

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18
Q

What organism causes Giardia?

A

Giardia intestinalis (lamblia, duodenalis)

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19
Q

What is the mode of transmission of E. histolytica?

A

Fecal-oral, but usually from ingesting contaminated water or food

20
Q

What is the mode of transmission of Giardia?

A

Person to person, or water-borne/food-borne outbreak

21
Q

What are clinical features of Giardiasis?

A 
Watery, foul smelling diarrhea
Abdominal distension, flatulence, cramps, anorexia
Chills, low-grade fever, weight loss
Blood and mucus not found in stool
Can be asymptomatic cyst passer
22
Q

How is giardiasis diagnosed?

A

Stool microscopic examination, tests for stool antigen

23
Q

Treatment for Giardiasis?

A

Metronidazole, tinidazole

Paromomycin

24
Q

How can you differentiated Cryptosporidium from Cyclospora microscopically?

A

Cyclospora autofluoresces under UV light

25
Q

What is the life cycle of Cryptosporidium?

A
  • Cyst is ingested
  • Excystation in small bowel
  • Replicates intracellularly but extracytoplasmically (creates own environment in tip of cells of brush border)
  • Cysts excreted
26
Q

Is there an animal host of cryptosporidium?

A

NO, disease only in human

27
Q

What is the mode of transmission of cryptosporidium?

A

Fecal-oral route

Usually from treated water (recreational pools, parks, sometimes drinking water, not streams/ponds)

28
Q

Why can’t an immunocompomised host clear cryptosporidium?

A

Since organism replicates intracellularly, requires cellular immunity to interrupt replication

29
Q

What is the clinical presentation of cryptosporidium in an immunocompetent host?

A

Watery diarrhea

Less common: cramps, nausea, anorexia, fever

30
Q

What is the clinical presentation of cryptosporidium in an immunocompromised host?

A

Voluminous watery diarrhea, up to 15 bowel movements a day and 10 liter fluid loss

31
Q

How is cryptosporidium diagnosed?

A

Fluorescent antibody test
Modified acid-fast stain
Giemsa stain

32
Q

What is the treatment of cryptosporidium in immunocompetent host?

A

Supportive therapy

Nitazoxanide (not usually necessary)

33
Q

What is the treatment of cryptosporidium in an immunocompromised host?

A

Best treatment = reversal of immune suppression with ART

Can try nitazoxanide, paromomycin, azithromycin

34
Q

Can chlorine get rid of cryptosporidium in water?

A

NO

35
Q

What is unique about the morphology of Trichomonas vaginalis?

A

Only trophozoite form, no cysts

36
Q

What is the mode of transmission of Trichomonas vaginalis?

A

Sexually transmitted

37
Q

What is the common clinical presentation of Trichomonas vaginalis?

A

Women: vaginal discharge, vulvovaginal soreness, dysuria, can be asymptomatic
Men: asymptomatic or mild urethral discharge

38
Q

How does Trichomonas vaginalis increase risk for HIV?

A
  • Weakens integrity of epithelial barrier
  • Decreases innate immunity and normal epithelial defenses
  • Disrupts lactobacilli-dominated vaginal microbiome
  • In males infected with HIV, co-infection with trichomoniasis causes 6x increase in HIV viral load in semen
39
Q

How is Trichomonas vaginalis diagnosed?

A

Wet mount microscopy
Cultures
RNA probe

40
Q

Treatment for Trichomonas vaginalis

A

Metronidazole or tinidazole (for both partners)

41
Q

What is the mode of transmission of Cyclospora?

A

Fecal-oral

Contaminated water and food (basil, raspberries) outbreaks

42
Q

What is the life cycle of cyclospora?

A

Ingest oocyst
Sporozoites reside in epithelial cells of small bowel
Excrete oocysts

43
Q

What is the clinical presentation of cyclospora infection?

A

Sudden onset
Fever, cramping
Watery diarrhea
Can last weeks if untreated

44
Q

How is cyclospora diagnosed?

A

Stool specimen microscopy (acid fast or safranin stain)

PCR for parasite DNA

45
Q

Treatment for cyclospora

A

TMP-SMX

Parasitology/Virology (19 decks)

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