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(MUL Parasitology) > 21. Protozoa (Entamoeba) > Flashcards

21. Protozoa (Entamoeba) Flashcards

1
Q

what disease is caused by Entamoeba histolytica?

A

Amoebiasis

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2
Q

what is amoebiasis/amoebic dysentery?

A

harbouring of protozoa E. histolytica inside the body with or without disease symptoms

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3
Q

what is the name of the invasive form of Entamoeba?

A

E. histoytica

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4
Q

what is the non-invasive form of Entamoeba?

A

E. dispar

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5
Q

where is Entamoeba histolytica most common?

A

in the tropics and subtropics (up to 60%)

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6
Q

________ diminishes with treatment, but _______ remains.

A

Mortality

morbidity

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7
Q

what is Amoebiasis’ rank in parasitic causes of death worldwide?

A

third parasitic cause of death after malaria and schistosomiasis

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8
Q

Entamoeba histolytica is a _______ virulent pathogen

A

facultative

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9
Q

what is the percent of infected people that actually get the disease?

A

10%

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10
Q

what are the two types of infection?

A
  • extra-intestinal

- intestinal, mild to severe

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11
Q

what are the modes of transmission of Amoebiasis?

A
  • Direct contact of person to person (fecal‐oral)
  • Food or drink contaminated with feces containing the E. histolytica cyst
  • Use of human feces (night soil) for soil fertilizer
  • Transmission among homosexuals (oral‐anal)
  • Contamination of food by flies and possibly cockroaches
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12
Q

what are the host specificities of Amoebiasis?

A
  • All age groups affected
  • No gender or racial differences
  • Institutional, community living
  • Disease severe in children, old, and pregnant women
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13
Q

what are the common environmental conditions that allow for prevalence of E. histolytica?

A
  • Low socio‐economic
  • Poor sanitation, sewage leakage
  • Night soil for agriculture
  • Seasonal variation
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14
Q

what are the two stages of the Entamoeba histolytica life cycle?

A
  • trophozoite: vegetative stage

- cyst: infective stage

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15
Q

what are two environmental characteristics of the trophozoite stage?

A
  • it must encyst to survive the environment. it is a fragile structure
  • it is a strict anaerobe
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16
Q

what are the environmental characteristics of the cyst stage?

A
  • resistant to the harsh conditions of the environment
  • sensitive to heat and freezing; last a few months in water
  • resistant to chlorine; remove via flocculation/filtration
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17
Q

which of the two stages is:

  • passed in feces
  • resistant
  • infective
A

cyst

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18
Q

which of the two stages is:

  • feeding
  • motile
  • replicative
A

trophozoite

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19
Q

how many cysts are necessary for infection?

A

only 1 cyst, making it the most efficient pathogenic protozoa

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20
Q

what is the name of the vegetative stage?

A

trophozoite

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21
Q

what is the morphology of the E. histolytica nucleus?

A
  • spherical, containing central karyosome

- on the inner surface membrane, evenly distributed small chromatin dots

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22
Q

what is contained in the food vacuoles?

A
  • leukocytes
  • bacteria (which they feed on)
  • maybe RBCs
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23
Q

what is the morphology of the pre-cyst stage of Entamoeba histolytica?

A

‐ Round or oval
- blunt pseudopodia
‐ Single nucleus present

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24
Q

what is the morphology of the cyst stage?

A

‐ Four nuclei are present in mature quadrinucleated cyst

‐ Glycogen mass & chromatoid bodies are present in immature cysts – disappear in mature ones

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25
Q

what is the morphology of the karyosome?

A
  • located in the center of the nucleus

- probably contains DNA

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26
Q

what do the chromatid bars look like?

A
  • they are seen in cysts

- they are blunt rods or splinter shape. They eventually disappear as the cyst ages.

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27
Q

what is the mitosome?

A

remnant mitochondrion

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28
Q

what kind of membrane does the mitosome have?

A

a double membrane, like mitochondria

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29
Q

how are proteins delivered to the mitosome?

A

by a targeting sequence of amino acids

30
Q

what do mitosomes have different from mitochondria?

A
  • they do not have genes within them

- the genes for the mitosomal components are contained in the nuclear genome

31
Q

what is the morphology of the vacuoles?

A
  • they occupy a great proportion of the cytoplasm.

- they may contain cellular debris, red blood cells, bacteria, or contain nothing

32
Q

there are at least 5 types of vacuoles. what are the 5?

A
  1. phagocytic
  2. macropinocytic
  3. micropinocytic
  4. primary lysosomes
  5. secondary lysosomes
33
Q

what are the two types of pathogenesis in E. histolytica?

A
  • non-invasive

- invasive

34
Q

what characterizes non-invasive ?

A
  • ameba colony on intestinal mucosa
  • asymptomatic cyst passer
  • non‐dysenteric diarrhea, abdominal cramps, other GI symptoms
35
Q

what characterizes invasive?

A
  • necrosis of mucosa –> ulcers, dysentery
  • ulcer enlargement –> dysentery, peritonitis
  • metastasis –> extraintestinal amoebiasis
  • cessation of cyst production
36
Q

what does pathogenesis depend on?

A
  • parasite virulence
  • host resistance
  • condition of the intestinal tract
37
Q

where can the non-pathogenic parasites be found in the intestine?

A

in the lumen

38
Q

where can the pathogenic parasites be found in the intestine?

A

trophozoites invade the intestinal mucosa

39
Q

what do trophozoites produce? what pathology does this induce?

A

histolytic enzyme - it produces necrosis of the mucosa leading to the formation of flask-shaped ulcers

40
Q

where do trophozoites exist in the pathogenic form?

A

in the base of the flask shaped ulcer

41
Q

what is found in the pathogenesis of intestinal amoebiasis?

A
  • Unique ability to hydrolyse host tissues with their active cysteine proteases present on the surface membrane of the trophozoite.
  • Lesions are found in the caecum, appendix, or colon. They may heal. If perforation of the colon occurs, there is a peritonitis that can lead to death.
42
Q

define Amoeboma

A
  • granuloma obstructing the bowel due to the pathogenesis of E. histolytica
  • is a mass under oedematous mucosa with:
    - internal abscesses of necrotic tissue and amoebae
    - outer firm nodular fibrous tissue
43
Q

Amoeba cells can live and multiply indefinitely within the ________ of the mucosa of the large intestine

A

crypts

44
Q

They are able to invade the ____________, which constitute a major non‐specific defense immune mechanism

A

mucous layer

45
Q

They feed on _______ and __________________ and interacting metabolically with enteric bacteria

A

starches

mucous secretions

46
Q

how do the parasites initate tissue invasion?

A

when they hydrolyse mucosal cells and absorb the pre-digested products

47
Q

why do they hydrolyse mucosal cells?

A

so that they can absorb the pre-digested products and not have to feed on bacteria

48
Q

how does the parasite adhere to the enterocyte?

A

Gal/GalNAc lectin

49
Q

what does the activation of the amoebic virulence program consist of?

A

amoebic cysteine proteases

50
Q

neutrophils will respond to the parasite. which cytokine causes their recruitment in this case?

A

IL-8 and other chemoattractants

51
Q

what is the issue with neutroohil migration in amoebiasis?

A

they migration damages the epithelial barrier

52
Q

how do the Amoeba invade between the cells?

A

they use their cysteine proteases to cleave extracellular matrix proteins and invade

53
Q

what are the 4 types of pathologies/lesions found in the pathogenesis of E. histolytica? ***

A
  • perforation, hemorrhage (rare)
  • secondary infection
  • amoeboma (rare)
  • extraintestinal lesions
54
Q

what characterises an Amoeboma?

A
  • clinically stimulates a neoplasm
  • intussusception
  • obstruction
55
Q

what is extra-intestinal amoebiasis?

A
  • metastasis via blood stream
  • primarily liver (portal vein)

– other sites less frequent

  • amoeba‐free stools common
  • high antibody titers
56
Q

what are two extra-intestinal amoebiasis pathologies?

A
  • pulmonary amoebiasis

- cutaneous amoebiasis

57
Q

define pulmonary amoebiasis

A
  • rarely primary
  • rupture of liver abscess through diaphragm
  • Secondary bacterial infections common
  • fever, cough, pain
58
Q

define cutaneous amoebiasis

A
  • intestinal or hepatic fistula
  • mucosa bathed in fluids containing trophozoites
    –perianal ulcers
    –urogenital (e.g. labia,
    vagina, penis)
59
Q

how is amoebiasis diagnosed?

A
  • Microscopy: cannot distinguish cysts between E. histolytica and E. dispar
  • Immuno‐fluorescence (IFA)
  • PCR – used less frequently since DNA is less available if stool samples preserved in formalin for long periods
60
Q

what consequence does infection have on the immune system?

A

long lasting antibody production

61
Q

how does metronidazole, and tinidazole affect the parasite

A
  • it is a tissue amoebicide

- it is very effecting in killing amoebas in the wall of the intestine, in blood in liver absesses

62
Q

how does diluxanide furoate affect the parasite?

A
  • it is a luminal amoebicide

- kills trophozoites and cysts in the lumen of the intestine

63
Q

what are the methods of primary prevention of E. histolytica?

A

‐ Safe fecal disposal
‐ Safe water supply
‐ Hygiene
‐ Health education

64
Q

how long do cysts remain viable in feces? in water?

A
  • days

- longer periods

65
Q

how are cysts killed?

A
  • dryness
  • heat over 55°C
  • NOT chlorine
66
Q

what are the methods of secondary prevention of E. histolytica?

A
  • early diagnosis

- treatment

67
Q

what is the main source of infection?

A

cyst passers (they pass many cyst and it only takes 1 to cause infection)

68
Q

is there a human vaccine for E. histolytica?

A

no

69
Q

how does the animal vaccine work?

A

Vaccinations using native and recombinant forms of the parasite Gal‐lectin have been successful in protecting animals in the lab against intestinal amoebiasis and amoebic liver abscess

70
Q

What part of the body is inhabited by E. histolytica?

A

inhabits large intestine

71
Q

what is the general life cycle of E. histolytica?

A

typical fecal-oral life cycle

(MUL Parasitology) (10 decks)

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