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Flagellates: Giardia lamblia Dientamoeba fragilis Chilomastix mesnili Trichomonas hominis Enteromonas hominis Retortamonas intestinalis Ameba: Entamoeba.

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Presentation on theme: "Flagellates: Giardia lamblia Dientamoeba fragilis Chilomastix mesnili Trichomonas hominis Enteromonas hominis Retortamonas intestinalis Ameba: Entamoeba."— Presentation transcript:

1 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 Other Lumen-Dwelling Protozoa Trichomonas vaginalis (urogenital) Trichomonas tenax (oral) Entamoeba gingivalis (oral) monoxenous vs heteroxenous


3 Giardia lamblia Taxonomy one human species, aka: G. duodenalis G. intestinalis morphologically similar forms in other mammals 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 1681van Leeuwenhoek observed 1859Lambl documented 1920sclinical symptoms, but controversial 1954Rendtorff fulfilled Kochs postulate

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 Infective stage passed in feces Replicative stage inhabiting sm. intestine TROPHOZOITE CYST

6 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 In Vitro Culture of Giardia 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 microtubules + microribbons lateral crest Attachment Mechanisms? contractile ring hydrodynamic force receptor mediated Adhesive Disk Components microtubules tubulin microribbons giardins lateral crest actin-myosin

9 Clinical Features and Symptoms 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 Subacute/Chronic recurrent diarrheal episodes cramps uncommon sulfuric belching, ano- rexia, nausea frequent can lead to weight loss and failure to thrive

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

11 Diagnosis 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 Treatment 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 Control 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

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%) 50-90% are asymptomatic mild dysuria or pruritus minor urethral discharge

17 DIAGNOSIS 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 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 Key Features of Trophozoites


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 7-15 mm trophozoite no cyst single nucleus axostyle 4 free flagella + undulating membrane costa Trichomonas hominis

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

26 Chilomastix mesniliT. hominis

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