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Intestinal Protozoa Flashcards

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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
Virulence factors - Amoebiasis
-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
Intestinal and Extraintestinal Amoebiasis symptoms
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
Liver abscess - due to Amoebiasis - causation
- 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
Lab ID - Amoebiasis
microscopy, culture, serologic testing, and (PCR) assay
29
Microscope and culture ID - Amoebiasis
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
Antigen detection - Amoebiasis
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
Molecular tests - Amoebiasis
Conventional and Real time PCR, LAMP
32
Intestinal Amebiasis: Treatment
``` 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
Giardiasis
Giardia intestinalis / Giardia lamblia / Lamblia intestinalis / Giardia duodenalis.
34
Amitochondriate
Lacking mitochondria
35
G lamblia - features
Amitochondriate flagellated protozoan Bilaterally symmetrical Most primitive eukaryotes in existence
36
Protozoa
Single celled eukaryote
37
Protozoa represent a unique type of evolution, how?
``` 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
Virulence factors - G lamblia
Infraciliature (skeleton): coordinating system of cilia. Rhoptries: penetration of cells (Apicomplexa). Cell covered in 3-layered Plasma membrane
39
Giardia - transmission
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
Giardia - Trophozoite morphology
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
Cyst - Trophozoite morphology
Cysts (protective, infective stage) • Cysts is ellipsoid; slightly smaller than trophozoites - have 4 visibly distinct nuclei. -median rod (axostyles), visible down the centre
42
Giardiasis is common in children and hikers (T/F)
True
43
Cysts susceptibility
Desiccation and direct sunlight
44
Mild to severe gastrointestinal signs | of Giardiasis
• Sudden onset diarrhea; Foul-smelling stools • Abdominal cramps • Bloating, flatulence •Nausea, fatigue • Weight loss -Lactose intolerance up to six months afterward
45
Lab ID - Giardiasis
``` •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
Giardiasis - Treatment
Anti-protozoal drugs • Metronidazole • Tinidazole •Ornidazole Chronic cases • May be resistant • Prolonged therapy may be necessary
47
Giardiasis - Prevention
``` Treat potential contaminated water -Boil water, filter (pore size 1 uL), chlorinate Wash fruits and veg Hand washing No swimming wks after exposure ```
48
Trichomonas vaginalis
Euprotista Small flagellates Only exist as trophozoites
49
T vaginalis - hosts
Hosts and Host Range: Humans (men & women)
50
Karyomastigont
Protozoa giving rise to 2 pairs of flagella
51
T vaginalis - morphology
Karyomastigont - 2 pairs flagella Parabasal - very Small cells accompanying T vaginalis Axostyle- runs diagonally through organism
52
Life Cycle - T vaginalis
1. Trophozoite 2. Binary fission 3. Direct transmission through sexual intercourse
53
T vaginalis - pathogenesis
- Remain and multiply in vagina and cause inflammation of the epithelium. - Excessive production of mucus; pain. Can invade other organs such as kidney
54
T vaginalis - lab ID
•Wet preparation: Microscopic examination of vaginal swab or urethral swabs observing for tumbling
55
Balantidium coli
Euprotista Phyllum: Ciliophora Largest protozoan parasite of humans Heterokaryotic (i.e. two kinds of nuclei)
56
B. coli - trophozoite reproduction
Trophozoites multiply by asexual binary fission or sexual conjugation (with the exchange of nuclear material).
57
Balantidiosis is common in areas near swine (T/F)
True
58
Trophozoites - B coli features
- oblong | - kidney shaped macronucleus and smaller micronucleus.
59
Cysts - B coli features
-round with a rounder and thicker macronucleus
60
B coli - life cycle
(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
Clinical features - Balantidiosis
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
Diagnosis - Balantidiosis
Microscopic examination of stool: Trophozoites and Cysts

Parasitology (10 decks)

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