1. INTESTINAL PROTOZOA monoxenous vs heteroxenous
Flagellates:
Giardia lamblia
Dientamoeba fragilis
Chilomastix mesnili
Trichomonas hominis
Enteromonas hominis
Retortamonas intestinalis
Ameba:
Entamoeba histolytica
Entamoeba dispar
Entamoeba coli
Entamoeba hartmanni
Endolimax nana
Iodamoeba bütschlii
Apicomplexa:
Cryptosporidium parvum
Cyclospora cayetanensis
Isospora belli
Microsporidia:
Enterocytozoon bieneusi
Encephalitozoon intestinalis
Other:
Blastocystis hominis
Balantidium coli
INTESTINAL PROTOZOA
monoxenous vs heteroxenous
Other Lumen-Dwelling Protozoa
Trichomonas vaginalis (urogenital)
Trichomonas tenax (oral)
Entamoeba gingivalis (oral)

3. Giardia lamblia worldwide distribution
higher prevalence in tropical or developing countries (20%)
1-6% in temperate countries
most common protozoa in stools
~200 million cases/yr
giardiasis
often asymptomatic
acute or chronic diarrhea
Historical Notes
1681 van Leeuwenhoek observed
1859 Lambl documented
1920’s clinical symptoms, but controversial
1954 Rendtorff fulfilled Koch’s postulate
Taxonomy
one human species, aka:
G. duodenalis
G. intestinalis
morphologically similar forms in other mammals

4. Fecal-Oral Transmission Factors
poor personal hygiene
children (eg, day care centers)
food handlers
developing countries
poor sanitation
endemic
travelers diarrhea
water-borne epidemics
male homosexuality
oral-anal contact
zoonosis?
Entamoeba =no
Cryptosporidium =yes
Giardia =controversial
Is giardiasis a zoonosis?
no definitive documentation
transmission between humans and dogs rare (J.Parasit. 83:44, 1997)
person-to-person trans-mission is most prevalent

5. Giardia Life Cycle TROPHOZOITE CYST Infective stage passed in feces
Replicative stage inhabiting sm. intestine

6. In Vitro Culture of Giardia
Excystation
brief exposure to acidic pH (~2)
flagellar activity within 5-10 min after return to neutral pH
breakdown of cyst wall (proteases)
trophozoite emerges from cyst
cytokinesis within 30 min
Encystation
exposure to pH 7, no bile
exposure to pH 7.8, high bile
cyst wall secretion (appearance of vesicles)
loss of disk and flagella
nuclear division

8. Adhesive Disk Components
microtubules + microribbons
lateral crest
Adhesive Disk Components
microtubules
tubulin
microribbons
giardins
lateral crest
actin-myosin
Attachment Mechanisms?
contractile ring
hydrodynamic force
receptor mediated

9. Clinical Features and Symptoms
Subacute/Chronic
recurrent diarrheal episodes
cramps uncommon
sulfuric belching, ano-rexia, nausea frequent
can lead to weight loss and failure to thrive
Range of Outcomes
asymptomatic/latent
acute short-lasting diarrhea
chronic/nutritional disorders
Acute Symptoms
1-2 week incubation
sudden explosive, watery diarrhea
bulky, frothy, greasy, foul-smelling stools
no blood or mucus
upper gastro-intestinal uneasiness, bloating, flatulence, belching, cramps, nausea, vomiting, anorexia
usually clears spontaneously (undiagnosed), but can persist or become chronic

10. Pathogenesis Possible Mechanisms epithelial damage villus blunting
crypt cell hypertrophy
cellular infiltration
malabsorption
enzyme deficiencies
lactase (lactose intolerance)
Possible Mechanisms
mechanical irritation
obstruction of absorption

11. Diagnosis Parasite Detection suspect: acute or chronic symptoms
confirmed: detection of parasite in feces or duodenal aspirate or biopsy
parasite easy to identify
parasite can be difficult to detect
inconsistent excretion in feces
patchy loci of infection
Parasite Detection
Stools
3 non-consecutive days
wet mounts or stained
IFA, copro-antigens
Aspirate or Biopsy
Enterotest (or string test)

12. Control Treatment avoid fecal-oral transmission
improve personal hygiene
especially institutions
treat asymptomatic carriers
eg, family members
health education
hand-washing
sanitation
food handling
protect water supply
treat water if questionable
boiling
iodine
not chlorine
Drug of Choice
metronidazole (Flagyl)
750 mg/tid/5d
>90% cure rate
Alternatives
tinidazole (single dose)
paromomycin (pregnancy)
quinicrine
furazolidone
Prognosis is good with no sequelae

13. TRICHOMONADS 3-5 anterior flagella one undulating membrane axostyle
hydrogensome (EM)

15. Trichomonas vaginalis
trophozoite stage transmitted during sexual intercourse
non-sexual contact possible
common STD
co-infection w/other STDs
more prevalent in at risk groups
associated with epithelium of uro-genital tract
females: vagina
males: urethra, prostate, epididymis
both sexes equally susceptible
symptoms more common in females
sexual intercourse

16. Trichomoniasis In females: In males:
ranges from asymptomatic, to mild or moderate irritation, to extreme vaginitis
50-75% abnormal discharge (frothy, yellowish or greenish)
25-50% pruritis
50% painful coitus
onset or exacerbation often associated with menstruation or pregnancy
vaginal erythema, ‘strawberry cervix’ (~2%)
In males:
50-90% are asymptomatic
mild dysuria or pruritus
minor urethral discharge

17. DIAGNOSIS TREATMENT PREVENTION demonstration of parasite
direct observation or in vitro culture
vaginal discharge
urine sediment
prostatic secretion
TREATMENT
metronidazole (Flagyl)
250 mg (3/d) for 5-7 days
single 2 g dose
simultaneous treatment of partner! (85-90% cure rate)
PREVENTION
limit # of sexual partners
condoms

18. Key Features of Cysts oval shape 11-14 x 6-10 m
distinct cell wall set apart from cytoplasm
4 nuclei at anterior end
large karyosome, no peripheral chromatin
fibrils (axonemes) evident
median bodies

21. Key Features of Trophozoites
pear shape
12-15 x 5-10 x 2-4 m
2 nuclei
large karyosome, no peripheral chromatin
fibrils (axonemes) evident
bilateral symmetry
pair of median bodies
adhesive disk (not always evident)
4 pair flagella
motility likened to falling leaf

23. Other Flagellates Found
in Human Feces
Dientamoeba fragilis
no flagella (discuss with amebas)
Pentatrichomonas hominis
formerly called Trichomonas hominis
Chilomastix mesnili
Enteromonas hominis
Retortamonas intestinalis

24. Non-Pathogenic Intestinal Flagellates
Trichomonas hominis
7-15 mm trophozoite
no cyst
single nucleus
axostyle
4 free flagella + undulating membrane
costa

25. Non-Pathogenic Intestinal Flagellates
Chilomastix mesnili
10-20 mm trophozoite
6-20 mm cyst
single nucleus
4 flagella
cytostome

26. T. hominis
Chilomastix mesnili