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)
Taxonomy one human species, aka: G. duodenalis G. intestinalis morphologically similar forms in other mammals 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
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 transmission is most prevalent
Giardia Life Cycle CYST TROPHOZOITE Infective stage passed in feces Replicative stage inhabiting sm. intestine
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
microtubules + microribbons lateral crest Adhesive Disk Components microtubules tubulin microribbons giardins lateral crest actin-myosin Attachment Mechanisms? contractile ring hydrodynamic force receptor mediated
Clinical Features and Symptoms Range of Outcomes asymptomatic/latent acute short-lasting diarrhea chronic/nutritional disorders Acute Symptoms Subacute/Chronic recurrent diarrheal episodes cramps uncommon sulfuric belching, anorexia, nausea frequent can lead to weight loss and failure to thrive 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
Pathogenesis epithelial damage villus blunting crypt cell hypertrophy cellular infiltration malabsorption enzyme deficiencies lactase (lactose intolerance) Possible Mechanisms mechanical irritation obstruction of absorption
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)
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
TRICHOMONADS 3-5 anterior flagella one undulating membrane axostyle hydrogensome (EM) Human Trichomonas Species T. tenax oral cavity T. hominis* intestine T. vaginalis uro-genital *aka: Pentatrichomonas
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
In females: In males: Trichomoniasis 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
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
Key Features of Cysts oval shape 11-14 x 6-10 µm distinct cell wall set apart from cytoplasm 4 nuclei at anterior end large karyosome, no peripheral chromatin fibrils (axonemes) evident median bodies
Key Features of Trophozoites pear shape 12-15 x 5-10 x 2-4 µm 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
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
Non-Pathogenic Intestinal Flagellates Trichomonas hominis 7-15 mm trophozoite no cyst single nucleus axostyle 4 free flagella + undulating membrane costa
Non-Pathogenic Intestinal Flagellates Chilomastix mesnili 10-20 mm trophozoite 6-20 mm cyst single nucleus 4 flagella cytostome
T. hominis Chilomastix mesnili