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Parasitology > Intestinal Protozoa > Flashcards

Intestinal Protozoa Flashcards

1
Q

List medically important protozoa and their diseases

A

(a) Amoebas: Entamoeba histolytica, Naegleria,
Acanthamoeba.
(b) Flagellates: Trypanosoma cruzi
(c) Sporozoa: Toxoplasma gondii

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2
Q

Protozoa - classify by motility

A

(a) Mastigophora (flagella) - Trypanosoma cruzi, Giardia lamblia
(b) Sarcodina (pseudopodia) - Amoebas
(c) Apicomplexa (microtubule complex, commonly
referred to as sporozoa) - Toxoplasma gondi, Plasmodium
(d) Ciliophora (ciliates) - Balantidium coli

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3
Q

Ciliophora spp

A

Balatidium coli

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4
Q

Apicomplexa spp

A 
Split into two categories 
Coccidia 
Isospora belli 
Toxoplasma gondii
Sarcocystis spp.
Cryptosporidium parvum 
Pneumocystis carinii
Piroplasma 
Plasmodium falciparum
Plasmodium vivax 
Plasmodium malariae
Plasmodium ovale
Babesia microti
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5
Q

Kinetoplastida spp

A 
(Flagellated)
Trypanosoma gambiense
Trypanosoma rhodiense 
Trypanosoma cruzi 
Leishmania spp
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6
Q

Amoebic abscess (amoebiasis, amoebic dysentery) agent, epidemiology

A

Agent: Entamoeba histolytica
E. dispar (non invasive)

Epidemiology 
Contaminated water
Poor sanitation - daycares  
Close proximity places - military barracks, nursing home, prisons 
Human waste as fertilizer
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7
Q

Entamoeba coli, E. hartmanii, Endolimax nana, Iodamoeba bütschlii non pathogenic to humans (T/F)

A

True

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8
Q

Amoebic abscess - transmission

A

–faeco-oral, food and water contaminated by flies/roaches, oral-anal sex

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9
Q

All cases of amoebic abscess are symptomatic

A

False

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10
Q

Amoebic abscess - Pathogenesis

A
  1. Cysts pass in stool of infected person
  2. Cysts ingested
  3. Cysts pass through stomach ->
    Gastric acid promotes trophozoite release in small intestine.
  4. Trophozoites multiply

((may cause necrosis + ulceration in the large intestine))

  1. Flask shaped ulceration = secondary bacterial infection/peritonitis due to damage to intestinal wall

If parasite moves to peritoneal cavity = goes to bloodstream -> goes to diff organs

(intermittent diarrhoea with abdominal pain and weight loss).

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11
Q

Virulence factor of amoebiasis, explain

A

Trophozoites invade BVs of the portal system,
surviving lytic complement & neutrophils.
Result: Gain access to the liver parenchyma.

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12
Q

What is second leading cause of mortality due to parasites?

A

Entamoeba histolytica

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13
Q

Possible parasitic cause of diarrhea in infants

A

E. moshkovskii

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14
Q

E. histolytica - host range

A

Mainly humans.

But: higher primates, dogs, cats and some rodents

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15
Q

Which Trophozoite has the foll description:
Trophozoites are round with large,
lobular pseudopodia and a clock-face nucleus.

A

E. histolytica

  • Central nucleus (most times)
  • Erythrocytes seen in cytoplasm means digested erythrocytes

Active, feeding stage

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16
Q

Describe cyst stage of E. histolytica

A

Cysts are smaller than trophozoites.
They have 4 nuclei and chromatoid bars (tightly
packed mRNA with rounded ends).

-Infective stage

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17
Q

What do E. histolytica and Entamoeba coli have in common?

A

They look alike

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18
Q

Why is it important to distinguish between E histolytica and E coli?

A

E coli is not pathogenic in the GIT but E histolytica is; need to know if treatment is necessary

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19
Q

E coli vs E histolytica

A

E. coli-coarser chromatin, eccentrically located
endosome (protein trafficking) and the absence of erythrocytes in the cytoplasm
-ingested erythrocytes appear as dark
inclusions.

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20
Q

Entamoeba coli cyst

A

-8 nuclei (compared to 4 nuclei seen in E. histolytica)
and
-smaller chromatid bodies that are often filamentous

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21
Q

E. histolytica - life cycle

A
  1. Ingestion of cysts
  2. Excystation in small intestine
  3. Division of quadrinucleate cyst
    into 4 and then 8 trophozoites
  4. Trophozoites move to colonize the colon
  5. Encystation
  6. Excretion of cysts
  7. Ingestion of cyst by the patient
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22
Q

Epidemiologic factors

A

Events, characteristics, or other definable entities that have the potential to bring about a change in a health condition.

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23
Q

Epidemiologic factors - Amoebiasis

A 
(i)Strain virulence -
classic strain, non-classic strain; Laredo ,
Huff; pathogen zymodemes
(ii) Susceptibility of the host
(iii) Nutrition status
(iv) Immune-system.
• Breakdown of immunologic barrier
(tissue invasion)
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24
Q

Virulence factors

A

Virulence factors:

  • assist and promote colonization of the host e.g. adhesins, invasins, antiphagocytic factors.
  • Bring damage to the host e.g. toxins, hemolysins, proteases
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25
Q

Virulence factors - Amoebiasis

A

-Secreting proteolytic enzymes (histolysin)
and cytotoxic substances.
• Contact-dependent cell killing
• Cytophagocytosis

Necrosis in amoebiasis is caused by trophozoite division and cytotoxin produced by E histolytica.

Amoebic killing target cell:
• Receptor-mediated adherence of amoebae
to target cell
• Amoebic cytolysis of target cell
• Amoebic phagocytosis of killed target cell
26
Q

Intestinal and Extraintestinal Amoebiasis symptoms

A

Intestinal amoebiasis - Diarrhea or dysentery, abdominal
pain, cramping , anorexia, weight loss, chronic fatigue

Extraintestinal amoebiasis - Systemic signs - fever, leukocytosis, abscess formation in right lobe, pain over liver, hepatomegaly

27
Q

Liver abscess - due to Amoebiasis - causation

A
  • seeding of infection from the bowel
  • infectious agents are carried to the liver
    from the portal venous circulation.
  • Necrosis of hepatocytes due to toxins
    of lysed neutrophils
  • liver abscess pus = chocolate brown -‘anchovy paste’.
  • Amoebas are to be found in the wall
    of the abscess
Complications of liver abscess
Secondary bact infection
Rupture into pleural space - Empyema
Rupture into pericardium - Pericarditis
Rupture into peritonium - Peritonitis
28
Q

Lab ID - Amoebiasis

A

microscopy, culture, serologic testing, and (PCR) assay

29
Q

Microscope and culture ID - Amoebiasis

A

Parasites concentrated in intestinal ulcers - one stool sample not as effective (need multiple stool samples)

Microscopic identification using:
Wet Mount (with or w/o iodine)
– a mature cyst has 4 nuclei, immature 1 – 3.

Trichrome stain
– Cysts, trophozoites can be stained for the location
of chromatoid bodies of the nucleus.

Culture: Using modified Locke-egg media
• culture less sensitive than microscopy

30
Q

Antigen detection - Amoebiasis

A

EIA kits.
Ag detection may be useful as an adjunct to microscopic
diagnosis in detecting parasites and to distinguish between pathogenic and nonpathogenic infections.

31
Q

Molecular tests - Amoebiasis

A

Conventional and Real time PCR, LAMP

32
Q

Intestinal Amebiasis: Treatment

A 
Asymptomatic amoebiasis (cyst passer):
Diloxanide furoate ( furamide) 500 mg tid/ 10 days
• Symptomatic amebiasis 
- Iodoquinol , 650 mg
tid/ 20 days or Metronidazole , 
750 mg tid/ 10 days;
Paramomycin.

Amebic colitis: Chloroquine, 250 mg bid

• Acute amebic dysentery: Emetine hydrochloride, 1mg/kg od IM or SC

Extraintestinal Amebiasis: Amebic liver abscess,

Ameboma:
Metronidazole, as above plus dihydroemetine / 10 days or Metronidazole or dihydroemetine as above plus Chloroquine ,
500 mg bid/ 2 days. Tinidazole, Ornidazole.

Surgical drainage – Drip and suck

33
Q

Giardiasis

A

Giardia intestinalis / Giardia lamblia / Lamblia intestinalis / Giardia duodenalis.

34
Q

Amitochondriate

A

Lacking mitochondria

35
Q

G lamblia - features

A

Amitochondriate flagellated protozoan
Bilaterally symmetrical
Most primitive eukaryotes in existence

36
Q

Protozoa

A

Single celled eukaryote

37
Q

Protozoa represent a unique type of evolution, how?

A 
Organelles are structures performing the
same functions as tissue and organs in “higher
organisms“. 
Locomotion and feeding: cilia, flagella,
pseudopodia. 
Osmoregulation: pulsatory vesicle,
contractile vacuole
38
Q

Virulence factors - G lamblia

A

Infraciliature (skeleton): coordinating system of cilia. Rhoptries: penetration of cells (Apicomplexa).
Cell covered in 3-layered Plasma membrane

39
Q

Giardia - transmission

A

Main host reservoir: Humans
Zoonotic transmission is possible but contraversial for Giardia spp
Epidemic form - drinking water
-Cysts infectious right after excretion
-Spread from person to person / oral-anally (carried to colon and encyst along the way)

40
Q

Giardia - Trophozoite morphology

A

8 flagella.
No mitochondria, or organelles for energy metabolism

This parasite is generally tear-drop shaped with two
visible nuclei.
Anterior region contains structure for epithelial cell attachment

41
Q

Cyst - Trophozoite morphology

A

Cysts (protective, infective stage)
• Cysts is ellipsoid; slightly smaller than trophozoites
- have 4 visibly distinct nuclei.
-median rod (axostyles), visible down the centre

42
Q

Giardiasis is common in children and hikers (T/F)

A

True

43
Q

Cysts susceptibility

A

Desiccation and direct sunlight

44
Q

Mild to severe gastrointestinal signs

of Giardiasis

A

• Sudden onset diarrhea; Foul-smelling stools
• Abdominal cramps
• Bloating, flatulence
•Nausea, fatigue
• Weight loss
-Lactose intolerance up to six months afterward

45
Q

Lab ID - Giardiasis

A 
•Direct observation in feces
-Trophozoites
         “Tear drop” shape
         Two nuclei and tumbling mobility
-Cysts
          Approximately 13μ long
          Oval, with 2-4 nuclei
  • Immunofluorescence
  • ELISA, PCR
46
Q

Giardiasis - Treatment

A

Anti-protozoal drugs
• Metronidazole
• Tinidazole
•Ornidazole

Chronic cases
• May be resistant
• Prolonged therapy may be necessary

47
Q

Giardiasis - Prevention

A 
Treat potential contaminated water
-Boil water, filter (pore size 1 uL), chlorinate 
Wash fruits and veg
Hand washing
No swimming wks after exposure
48
Q

Trichomonas vaginalis

A

Euprotista
Small flagellates
Only exist as trophozoites

49
Q

T vaginalis - hosts

A

Hosts and Host Range: Humans (men & women)

50
Q

Karyomastigont

A

Protozoa giving rise to 2 pairs of flagella

51
Q

T vaginalis - morphology

A

Karyomastigont - 2 pairs flagella
Parabasal - very Small cells accompanying T vaginalis
Axostyle- runs diagonally through organism

52
Q

Life Cycle - T vaginalis

A
  1. Trophozoite
  2. Binary fission
  3. Direct transmission through sexual intercourse
53
Q

T vaginalis - pathogenesis

A
  • Remain and multiply in vagina and cause
    inflammation of the epithelium.
  • Excessive production of mucus; pain.
    Can invade other organs such as kidney
54
Q

T vaginalis - lab ID

A

•Wet preparation: Microscopic examination of
vaginal swab or urethral swabs observing for
tumbling

55
Q

Balantidium coli

A

Euprotista
Phyllum: Ciliophora
Largest protozoan parasite of humans
Heterokaryotic (i.e. two kinds of nuclei)

56
Q

B. coli - trophozoite reproduction

A

Trophozoites multiply by asexual binary fission or sexual conjugation (with the exchange of nuclear material).

57
Q

Balantidiosis is common in areas near swine (T/F)

A

True

58
Q

Trophozoites - B coli features

A
  • oblong

- kidney shaped macronucleus and smaller micronucleus.

59
Q

Cysts - B coli features

A

-round with a rounder and thicker macronucleus

60
Q

B coli - life cycle

A

(1) Cyst
(2) Cyst ingested, swallowed
(3) Excysts (emerge from cyst), Trophozoites

(4) Division: Binary fission in small intestine. Trophozoite colonize large intestine, where they live in the
lumen and feed on the intestinal flora.

Some trophozoites invade the wall of the colon using proteolytic enzymes and multiply, and some of them return to the lumen.

(5) Form cysts -> feces

61
Q

Clinical features - Balantidiosis

A

Acute disease
-explosive diarrhea may occur as often as
every twenty minutes. Perforation of the colon may also
occur -> lead to life- threatening situations.

62
Q

Diagnosis - Balantidiosis

A

Microscopic examination of stool: Trophozoites and Cysts

Parasitology (10 decks)

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