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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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Entamoeba histolytica
(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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Cyclospora cayetanensis
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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Cyclospora cayetanensis
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
Entamoeba histolytica
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