Classification of protozoa

Transcription

1 Protozoa ( 原虫 )

2 General Account One-cell animal monocellular or unicellular organisms with full vital functions Species total named species:65,000; parasitic: around 10,000

3 Classification of protozoa Amoebae Flagellates Sporozoa Ciliates

4 Life cycle patterns One-host form 1. One stage form Trophozoite 2. Two stage form Trophozoite & Cyst Two-host form 1. Mammals mammals 2. Mammals insect vectors

5 Mode of Reproduction Asexual Reproduction Binary fission result in 2 daughter cells Schizogony multiple fission result in multiple cells Budding Exogenous budding - by external budding result in multi- cells Endodyogony - by internal budding result in 2 cells Sexual Reproduction Conjugation exchange of nuclear material of 2 Gametogony sexually differentiated cells unite -- zygote

6 Pathogenesis Host Resistance Innate immunity Acquired immunity Parasite Invasion Toxin Mechanically damage Immune impair Immune inhibition hypersentivity Opportunistic & Accidental (protozoa) infections

7 Opportunistic parasites Opportunistic infection An infection by a microorganism that normally does not cause disease but becomes pathogenic when the body's immune system is impaired and unable to fight off infection

8 Amoebic Infections Entamoeba histolytica Acanthamoeba Naegleria

9 Epidemiology 4th leading cause of death from parasitic diseases worldwide Organism # of deaths/yr # infected Entamoeba ~75,000 ~300 million Ascaris ~200,000 ~480 million Schistosoma ~750,000 ~200 million Plasmodium 2-3 million ~500 million (Malaria) Amoebiasis is not restricted to the tropics and subtropics, it also occurs in temperate and even in arctic and antarctic zones

10 Contaminated water is a source of infection.

11 Infection is common in developing countries where sanitation is poor.

12 Amoeba in alimentary tract Entamoeba E. histolytica (pathogenic) E. dispar (non-pathogenic) E. coli (big sister) E. hartmani (little brother) E. gingivalis (oral) Endolimax nana (occasionally pathogenic) Iodamoeba butschlii

13 Morphology Entamoeba histolytica Cysts Thick wall Trophozoites Plasmalemma (thin) 1-4 ring-like nuclei 1 ring-like nucleus Chromatoid body (blunt) Round, μm Concentratable Lacking Irregular, μm Labile

14 Endoplasma Ingested RBC Morphology Ectoplasma Nucleus with central karyosome and finely divided chromatin granules Pseudopod E. histolytica trophozoite

15 Morphology Trophozoites Single nucleus with a central, dot-like karyosome

16 Micrograph of a trophozoite ingesting a red blood cell deprived from its host.

17 Morphology 1-4 ring-like nuclei with finely divided peripheral chromatin Cyst wall and round shape Mature E. histolytica Cyst

18 Morphology

19 Morphology E. Coli trophozoites

20 E. Coli cysts Morphology

21 E. histolytica Stages - CYSTS Infective Stage for humans Resistant walls maintain viability If moist can last several weeks Killed by desiccation or boiling Diagnostic Stage in formed stools Can be concentrated and stained easily Not seen in liquid (diarrheic) stools or tissues

22 E. histolytica Stages - TROPHOZOITES Cause amoebiasis (damage tissue) Spread throughout the body, but... Rarely transmit the infection to others Labile in liquid stools or tissue, and must be rapidly found or preserved (quick fixation & cold storage) for Diagnosis

23 Life cycle

24 Life cycle Humans acquire E. histolytica by: Ingesting cysts (4 nuclei mature) in fecally contaminated food or water Rarely by directly inoculating trophozoites into colon or other sites (anal sex?) Fecal-Oral transmission (hand to mouth)

25 Life cycle The basic generation-cycle: cyst lumen trophozoites cyst Trophozoites may invade intestine and spread Cyst formation essential factors: enviroment + time Infective cysts and trophozoites pass in feces

26 Pathogenesis General Types of Virulence Factors: Adherence factors 260kDa Gal/GalNAc lectin Invasion factors Amoeba pores Cysteine proteinases Endotoxins

27 Pathogenesis Trophozoites... Attach to mucosal epithelial cells (MEC) Lyse MEC Ulcerate and invade mucosa Cause dysentery (diarrhea + blood) Metastasize via blood &/or lymph to Form abscesses in extraintestinal sites...

28 Clinical manifestation Pinpoint lesion on mucous membrane Flask-shaped crateriform ulcers Pathological changes in large intestine

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30 Ulcers caused by invasion of E. histolytica into the liver. Clinical manifestation

31 Clinical manifestation

32 Clinical manifestation

33 An Amoebic Liver Abscess Being Aspirated. Note the reddish brown color of the pus ( anchovy-sauce ). This color is due to the breakdown of liver cells. Gross pathology of amoebic abscess of liver. Tube of "chocolate" pus from abscess.

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35 X-ray of Amoebic Liver Abscess Clinical manifestation

36 Clinical Classification of Amoebiasis (World Health Organization) Asymptomatic infection (carrier) >90% (E. dispar?) Symptomatic cases <10% 8% -10% dysentery, colitis, etc 2% invasive amoebiasis 0.1% deaths

37 Clinical classification Asymptomatic Infection:"Cyst Passers/carrier Symptomatic Infection: Intestinal Amoebiasis: (colon and rectum 盲肠 升结肠 直肠 乙状结肠和阑尾 ) Acute Dysenteric (dysentery) Chronic Non-Dysenteric ( self-cured ) Extra-Intestinal Amoebiasis: Amoebic Liver Abscess (ALA) Amoebic Pulmonary Abscess Other sites (brain, skin, GU,?)

38 Acute Dysenteric Amoebiasis Symptoms: Bloody mucoid diarrhea RBCs and few WBCs in stools Abdominal pain weight loss bloating, tenesmus( 里急后重 ) and cramps Clinical manifestation

39 Acute Dysenteric Amoebiasis Clinical manifestation Signs: Fever (33%) Tender (enlarged) liver Stools positive for trophozoites +/- WBC NO cyst in loose stools

40 Chronic Non-Dysenteric Amoebiasis self-cured carrier state Usually for 1 year, 37% symptomatic >5 years Intermittent diarrhea, mucus, abdominal pain, flatulence and/or weight loss E. histolytica trophs in loose stools Cysts in solid stools Clinical manifestation Positive serology and ulcerations on sigmoidoscopy or pathologic test

41 Extra-Intestinal Amoebiasis Clinical manifestation Amoebic Liver Abscess (ALA) Symptoms History of dysentery (1 yr), weight loss, abdominal pain, chest or shoulder pain Signs fever, hepatomegaly Diagnostic aspiration:non-odorous, reddish-brown in color aspirate (chocolate jam) "anchovy paste" Might find trophozoites in the aspirate Skin inflammation

42 Diagnosis Pathogenic diagnosis Stool examination: Direct Fecal Smear (trophs and cysts) Fecal concentration and iodine dye techniques - (cysts) ZnSO 4 or formalin-ether Cultivation DNA detection Sigmoidoscopy Serologic Tests (for chronic disease): ELISA, IHA (indirect hemagglutination) Imaging: X-ray; CT

43 Stool examination trophozoite cyst specimen loose feces solid feces method diseases remarks direct smear with normal saline amoebic dysentery 1.container must clean 2.examined soon after they have been passed. 3.select bloody and mucous portion. direct smear with iodine stain chronic intestinal amoebiasis or carriers

44 Two microscopically indistinguishable Entamoeba sp. E. histolytica invades tissues should always be treated E. dispar is non-pathogenic, even in AIDS should not be treated

45 Treatment of Amoebiasis For invasive forms: metronidazole( 甲硝唑 ) For luminal forms: Iodoquinofonum( 喹碘方 ) paromomycin( 巴龙霉素 ) diloxanide( 二氯尼特 ) Do not treat asymptomatic intestinal E. dispar infection

46 Treatment of Amoebiasis Location Clinical Class Drug Name Drug Action Intestinal Asymptomatic Iodoquinofonnum( 喹碘方 ) lumenal amebicide Mild to moderate intestinal disease Metronidazole( 甲硝唑 ) tissue amebicide Severe intestinal disease Metronidazole plus a lumenal drug both Extraintestinal Hepatic disease Metronidazole plus a lumenal drug both

47 Prevention & Control Individual measures Diagnosis and treatment of E. histolytica patients Safe drinking water (boiling or 0.22 µm filtration) Cleaning of uncooked fruits and vegetables Prevention of contamination of foods Chemotherapeutic Trial

48 Prevention & Control Community measures Public services and utilities Adequate disposal of human stools Safe and adequate water supply Primary health care systems Health education (washing hands, cleaning and protecting food, controlling insects) Specific surveillance programs and Control programs integrated into ongoing sanitation & diarrhea control Health Regulations Control of food vendors and food handlers Control of flies and cockroaches

49 Infections with Free Living Amoebae Naegleria 耐格里属 Acanthamoeba 棘阿米巴属

50 Naegleria Free Living Amoebae Not seen in humans µm (smaller than A. spp.) with lobate pseudopodia i µm with filiform pseudopodia i i Acanthamoeba cysts & trophs are seen in humans

51 Acanthamoeba spp. Acanthamoeba trophozoites with acanthopodia

52 Primary Amoebic Meningoencephalitis PAME An acute suppurative infection of the brain and meninges that is rapidly fatal and usually not diagnosed antemortem Caused by Naegleria fowleri Headache, lethargy and olfactory problems Sore throat, runny nose, severe headache, vomiting, stiff neck, confusion leading to... Coma and death

53 DIAGNOSIS PAME Patient History (child) Prior Health Excellent Recent History of Swimming (fresh water/pools) Cases peak during HOT months Symptoms/Signs Sore throat, runny nose, headache, vomiting, stiff neck, mental confusion, olfactory problems, lethargy, coma and death

54 Treatment PAME None effective - few patients survive Amphoteracin B +/-?

55 Granulomatous Amoebic Encephalitis GAE A more slowly progressive, chronic form of the disease not associated with swimming (except in hot tubs) cause: Acanthamoeba castellanii history of subcutaneous nodules, eye or skin infection, progressive nasal congestion, headache... CNS lesions with negative serology for toxoplasmosis in debilitated/immuno-compromised Pts with CD4+ TL <200/mm 3 disseminated infection: skin, sinuses, lungs, CNS/CSF

56 Pathology abscesses/lesions (tissues) have GAE granulomatous inflammation hemorrhagic necrosis and vasculitis trophozoites & cysts with wrinkled-walls! amoebae rarely seen in CSF

57 Treatment GAE No satisfactory or effective treatment? amphotericin B

58 Acanthamoeba Keratitis AK Corneal infection with Acanthamoeba spp. trophozoites & cysts Ulcerations & Ring Infiltrate of cornea Induced by trauma to eye, exposure to contaminated H 2 O contact lens wear with tap water rinsing

59 Diagnosis AK Examine corneal scrapings or smear Histopathologic examination of cornea Treatment Triple Antiamoebic Therapy neomycin-polymyxingramicidin/propamidine/miconazole Penetrating keratoplasty (cadaver cornea)