Lecture1 Protozoa- 2008

8/4/2019 Lecture1 Protozoa- 2008

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Clinical Parasitology

Tropical Medicine

International Health

J Dick MacLean

www.medicine.mcgill.ca/tropmed


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ParasitologyClinical parasitology

Tropical Disease

Epidemiology

International Health

MicrobiologyClinical microbiology

Infectious Disease

Epidemiology

Public Health


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Institute of Parasitology, Macdonald Campus

McGill Centre for Tropical Disease, MGH

Department of Microbiology, Lyman Duff

International Health Office, Dept of Epidemiology


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Protozoa

Nematode

Cestode

Trematode


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Have you ever had one of these

parasites?

Yes

Nev

er

May

be

Don

tkno

w

Youv

egot

t...

20% 20% 20%20%20%1. Yes

2. Never

3. Maybe

4. Dont know

5. Youve got to be

kidding


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Kingdom Animalia

Subkingdom Protozoa

Phylum Sarcomastigophora

Phylum Apicomplexa

Phylum Ciliophora

Phylum Microspora

Subkingdom MetazoaPhylum Nematoda

Phylum Platyhelminthes

Taxonomy


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INTESTINE

Entamoeba histolyticaGiardia

Isospora

Cryptosporidium

Cyclospora

Strongyloides

Ascaris

Trichuris

hookworm

tapeworms

intestinal flukes

SYSTEMIC

Toxoplasmamalaria

filaria

Toxocara

hydatid cysts

cysticercosis

Schistosoma

liver flukes

Protozoa

Nematodes

Cestodes

Trematodes


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Intestinal protozoa


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Protozoa

..eukaryote..has genetic material encased in

a nuclear membrane (unlike bacteria and

viruses)

..classified traditionally by morphology

(eg. organelles of locomotion), life

cycle and mechanisms of

reproduction etc.


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Kingdom Animalia

Subkingdom Protozoa

Phylum Sarcomastigophora

Subphylum Sarcodina Entamoeba

Subphylum Mastigophora GiardiaPhylum Apicomplexa Cryptospotidium

Phylum Ciliophora Balantidium

Phylum Microspora microsporidium

Taxonomy


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Mastigophora: movement with flagella - e.g. Trichomonas,Giardia

Sarcodina: pseudopodia, e.g. Entamoeba histolytica

Apicomplexa: apical complex, no locomotor apparatus;sexual reproduction, e.g. cryptosporidium,

malaria, toxoplasma

Ciliophora: movement with cilia, e.g. Balantidium.


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INTESTINAL PROTOZOA

Pathogenic

Entamoeba histolytica

Balantidium coli

Giardia lambliaDientamoeba fragilis

Cryptosporidium parvum

Enterocytozoon bieneusiSeptata intestinalis

Cyclospora cayetanensis

Isospora belli

Commensal

(non-pathogenic)

Entamoeba hartmani

Entamoeba dispar

Entamoeba coliEndolimax nana

Iodamoeba btschlii

Chilomastix mesniliTrichomonas hominis

Blastocystis hominis


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Trophozoite: any stage in a protozoans life cycle

which can ingest food. In practice also

refers to the motile form.

Cyst: the non motile form which is protected by

a distinct membrane or cyst well. This is

an infective stage of the parasite.

Excystation: the process of emergence of the

trophozoite from the cyst (vs.

encystation)

Pseudopod: literally means false foot; temporary

cytoplasmic processes at the surface of

the trophozoite


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Intestinal protozoa


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(amoebiasis)

Subphylum Sarcodina


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trophozoite

cyst trophozoite

No stain

Hematoxylin stain


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AMOEBIASIS

1) assymptomatic carrier state

2) acute amoebic dysentry

3) amoebic liver abscess

4) amoeboma


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Amoebic dysentery

Presentation

Bloody, mucousy diarrheaFever

Abdominal pain

Diagnosis

Amoebic (hematophagous trophozoites) in stoolMixed WBCs in stool

Patchy inflammation seen on colonoscopyStool PCR or antigen capture


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Entamoeba histolytica trophozoite with ingested RBCs

hematophagous


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Anchovy paste


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AMOEBIC LIVER ABSCESS

Presentation

1. persisting fever

2. RUQ or epigastric pain and/or shoulder pain3. rarely diarrhea

Diagnosis1. ultrasound

2. raised WBC

3. serology4. aspirate microscopy

5. response to metronidazole 750 t.i.d.


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Laboratory problems

1. sensitivity

2. specificity


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Sequential Stool Examination for E. histolytica

1 2 3 4 5

direct 13 25 34 43 50 %

direct andconcentration

21 38 51 61 69 %

direct, concentration

and stain

41 65 79 88 93 %


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Cogwheel distribution of chromatin and central karyosome

Entamoeba . histolytica


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Entamoeba histolytica or dispar

E. histolytica (~10%) E. dispar (~ 90%)

(antigen capture, PCR, culture and zymodemes)


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Drugs for Entamoeba histolytica

Tissue: ..metronidazole, tinidazole, secnidazole, ornidazole

..emetine..dehydroemetine

..chloroquine

Bowel lumen: ..paromomycin (Humatin)

..diiodochlorhydroxyquin (Diodoquin)

..diloxanide furoate (Furamide)


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Epidemiology ofEntamoeba histolytica

Humans the only source (not a zoonosis)

Fecal-oral transmission

Our understanding is in transitionbecause of mis-identified cases.

E. histolytica/dispar

from developing countries is ~10%E. histolytica;

from developed countries is ~1%E. histolytica


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Which finding doesnt fitE.

histolytica amoebiasis ?

HighWhit

ec...

Ent

eritis

Coli

tis

Bloo

dins

tool

WBC

sins

tool

Rights

hould

e...

13%

7%

20%

23%

13%

23%

1. High White count

2. Enteritis

3. Colitis4. Blood in stool

5. WBCs in stool6. Right shoulder pain


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Giardia lamblia

Subphylum

mastigophora


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Giardia on small intestine mucosa


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Normal

small intestine mucosa


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Villus atrophy and

crypt hyperplasia


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Giardia epidemiology:

- fecal oral spread

- prevalence 3-5% in Canada; increased intravellers, backpackers, institutions, day

care centres- zoonosis - found in most mammals; esp.

beaver (beaver fever), cattle, cats,dogs, etc.

GIARDIASIS


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GIARDIASIS

Symptomsdiarrhea

flatulence

abdominal cramps

decreased appetite

+ weight loss

+ nausea

no fever

Signsmild abdominal

tenderness

Laboratoryno leukocytes in

stool

no mucous in stool

giardia cysts/trophsintermittent in stool

giardia cysts/trophsin duodenal aspirate


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Giardia treatment

Metronidazole 250-750 mg tid x 7-10 days

Atabrine 100 mg tid x 10 days


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Giardia causes which?

Gas

Fever

Dy

senter

y

WBCsi

nthe

stool

Coli

tis

Beaverco

nstipa

tion

7%

17%

13%

23%

13%

27%

1. Gas

2. Fever3. Dysentery

4. WBCs in the stool5. Colitis

6. Beaver constipation


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Cryptosporidium parvum

Phylum apicomplexa


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Cryptosporidium 3-5 microns


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CRYPTOSPORIDIUM


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CRYPTOSPORIDIUM

Epidemiology: - bovine reservoir (zoonosis)

- epidemic contamination of

municipal water

Biology: - lives in small intestine epithelialcell membrane

- Apicomplexa life cycle

Clinical: - diarrhea 2-3 weeks (chronic in

AIDS)- cholecystitis


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Phylum apicomplexa


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7-10 microns (Kinyoun acid-fast stain)


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Cryptosporidium 3-5 microns Cyclospora 7-10 microns


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Taxonomy: Apicomplexa

Epidemiology: in travellers to tropics (Nepal, Americas): raspberries, basil from Guatemala, Mexico

Biology: lives in small intestine epithelial cells

Clinical: prolonged diarrhea (2-6 wks)

Treatment: Septra


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Treatment of intestinal protozoa


Giardia

Cryptosporidium

Cyclospora

metronidazole

diloxanide furoate

diodohydroxyquinoline

metronidazole

atabrine

nil

Septra


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INTESTINAL PROTOZOA STAINS

1. Hematoxylin -E. histolytica, Giardia,

D. fragilis, Isospora

2. Modified Ziehl-Neelsen - Cryptosporidium

Cyclospora

3. Trichrome - Microsporidium

Trichomonas vaginalis


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Taxonomy: Mastigophora (like Giardia)

Epidemiology: reservoir is human

urogenital tract, sexual transmission

Biology: causes inflamation ofvaginal and urethral epithelium

Clinical: vaginal discharge

Treatment: metronidazole


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Concepts to rememberCommensalism (shared dinner table)

Zoonosis (inhuman life cycle)

Future challenges

1. Host immune reaction to protozoa2. The protozoans host immune avoidance

3. Laboratory diagnostic tools PCR, antigen capture,

proteomics4. Orphan drugs

5. Lack ofCryptosporidium treatment

Lecture1 Protozoa- 2008

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