寄生虫学：Protozoa 1

1、Medical Protozoa医学原虫,Assoc Prof. Dr. Lei Jiahui (雷家慧) Department of Human Parasitology,Teaching points,Introduction of medical protozoa Entomoeba histolytica (溶组织内阿米巴) Giardia lamblia (蓝氏贾第鞭毛虫) Trichomonas vaginalis (阴道毛滴虫),Introduction,about 65,000 species of protozoa a fifth (10,000 species) are p

2、arasitic some 40 species are parasitic in human,Introduction-Form and function,single cell,cytoplasm,cell membrane：fluid mosaic,Inclusion（内含物）,Organelles,Ectoplasm: gel-like Endoplasm: sol-like,Locomotory organelles,Nucleus: vesicular or compact,Locomotory Organelles（运动细胞器）,Pseudopod（伪足）,Flagellum（鞭

3、毛）,Cilium（纤毛）,Introduction - Reproduction,1. Asexual reproduction:,B. multiple fission,A. binary fission,Introduction - Reproduction,2. Sexual reproduction:,B. Gametogony,A. Conjugation,Introduction - Types of life cycle,Transmission among human without vector,Introduction - Types of life cycle,Tran

4、smission among human without vector Transmission via vertebrate vector,Introduction - Types of life cycle,Transmission among human without vector 2. Transmission via vertebrate vector 3. Transmission via arthropod vector,Introduction - Pathogenesis,Proliferation : breakage of cells and potential of

5、spread to far tissues and organs Opportunistic pathogenesis：infections with a mild or asymptomatic course in immunocompetent individuals, in the case of immunocompromised patients could cause severe syndromes or fatal outcome.,Phylum: Sarcodina Class: Labosea Order: Amoebida Family: Entamoebidae,Ent

6、amoeba histolytica 溶组织内阿米巴,Intestinal Amebae,Entamoeba E. histolytica (pathogen) E. Coli E. hartmani E. gingivalis (oral) Endolimax nana Iodamoeba butschlii,一、Morphology of E. histolytica Trophozoite Cyst,12 to 20 m in diameter Granular endoplasma Transparent ectoplasma with finger-like pseudopods,D

7、irectional motility,1. E. histolytica Stages - TROPHOZOITES,Are the motile, feeding stages that: Cause amebiasis (damage tissue) Spread throughout the body, but . Rarely transmit the infection to others are Labile in liquid stools or tissue, and must be rapidly found or preserved (quick fixation & c

8、old storage) for Diagnosis,chromatoid body,glycogen vacuole,Immature cysts,2. E. histolytica Stages - CYSTS,Usual Infective Stage for humans Resistant walls maintain viability If moist can last several weeks Killed by desiccation or boiling Usual Diagnostic Stage in formed stools Can be concentrated

9、 and stained easily Not seen in liquid (diarrheic) stools or tissues,二、 Life cycle of E. histolytica,mature cysts,trophozoites,cysts,Intestinal- or Extra-intestinal amoebiasis,三、Pathogenesis and clinic classification,Pathogenesis of Amebiasis,Trophozoites . Attach to mucosal epithelial cells (MEC) L

10、yse MEC Ulcerate and invade mucosa Cause dysentery (diarrhea + blood) Metastasize via blood &/or lymph to Form abscesses in extraintestinal sites .,A Adherence of amoeba to the intestinal mucus barrier. B Depletion of the mucus layer and disruption of the intestinal mucosa. C Penetration by the amoe

11、ba and lysis of epithelial cells and host inflammatory cells.,Clinical Classification of Amebiasis (World Health Organization),Asymptomatic (intestinal) : Cyst Passers” Symptomatic Infection:,Most common Infection may continue without clinical symptoms for weeks to months . May spontaneously resolve

12、 (self cure)/or Two types of E. histolytica may exist E. dispar (non-pathogenic) E. histolytica (pathogenic),1. Asymptomatic Amebiasis “Cyst Passers”,2. Symptomatic Infection,1) Intestinal Amebiasis (colon and rectum)- Two types Acute Dysenteric (dysentery) Chronic Non-Dysenteric ( “self-cured” or c

13、arrier state),Amebic Dysentery Symptoms: Bloody mucoid diarrhea ( “anchovy-sauce”pus) RBCs and few WBCs in stools Abdominal pain, cramps weight loss bloating, tenesmus,Acute Dysenteric Amebiasis:,Signs: Fever (33%) Diffuse abdominal tenderness Tender (enlarged) liver Stools positive for trophozoites

14、 +/- WBC NOT cysts in loose stools,Amebic Dysentery,Sigmoidoscopic appearance: Classic “Flask-Shaped” ulcer Sub-mucosal involvement is rare Adherent pseudomembrane overlying the Ulcerations,Amebic Dysentery,37% symptomatic 5 years Intermittent diarrhea alternate with constipation, mucus, abdominal p

15、ain, flatulence and/or weight loss Positive serology and ulcerations,Chronic Non-Dysenteric Amebiasis:,Intestinal Amebiasis Complications,Intestinal perforation and . Peritonitis - a surgical emergency Ameboma(阿米巴肿) Palpable mass of granulation tissue that may obstruct colon Toxic megacolon complica

16、tion of inappropriate steroid therapy,2. Symptomatic Infection,2) Extra-Intestinal Amebiasis Amebic Liver Abscess (ALA) Amebic Pulmonary Abscess Other sites (brain, skin, other organs),Symptoms dysentery (1 yr), wt loss, abdominal pain, radiated chest or shoulder pain Signs fever, hepatomegaly Thick

17、 reddish-brown （ “chocolate-jam” ） pus obtained by aspiration of the abscess,Amebic Liver Abscess (ALA),chocolate-jam liked aspiration,Amebic Liver Abscess (ALA),Complications Pulmonary Abscess: by direct extension through the diaphragm into thorax Rupture into the pleural cavity and/or hepatobronch

18、ial fistulas (瘘管)= trophozoites in sputum! Extension to other sites, including Peritoneum(腹膜), pericaridum, others,Amebic Liver Abscess (ALA),四、Diagnosis of Amebiasis,Diagnosis of Intestinal Amebiasis,Direct Fecal Smear Acute cases: trophs (quick,clean and warm specimens ) Chronic cases: cysts Sigmo

19、idoscopy（结肠镜检） Serologic Tests (for chronic disease),Laboratory Diagnosis of Hepatic Amebiasis,Examine stools for trophs/cysts (suggestive) Radiologic Studies (B ultrasonic checks, CT, NMR) Serologic tests (IHA or ELISA) Catheterize abscess and aspirate,五、Prevention and Treatment,Treatment of Amebia

20、sis,Prevention/Control of Amebiasis,吃熟食 喝开水 勤洗手,Source of infection Susceptible Route of population infection,Treatment,Blockade,Protection,Giardia lamblia （蓝氏贾第鞭毛虫）,Giardia intestinalis is probable the “correct” name. “Travelers diarrhea” caused by drinking stream water contaminated with Giardia cy

21、sts,1. Morphology of Giardia lamblia,12-15m long Symmetrical in shape a “badminton racket” “face of an old man”,Trophozoite,axostyle,flagella,sucking disk,nuclei,Note the adhesive discs on the ventral surface,convex on the dorsal surface,Roll on itself displaying “falling leaf” movement,Cyst oval an

22、d thick-walled 2-4 nuclei the axostyle is located in the midst of the parasite usual infective/diagnostic stage in formed stools,2. Life cycle,A single diarrheic stool can contain 14 billion parasites A stool in a moderate infection may contain 300 million cysts,3. Pathogenesis,1） Adherence to the m

23、ucosa and attack the microvilli 2） Interference with the absorption of fats and other nutrients 3） Mal-absorption syndrome and even cholecystitis,3. Pathogenesis,Symptoms Diarrhea (foul-smelling stool with the absence of pus and blood), dehydration, intestinal pain, bloating, and weight loss,4. Diag

24、nosis,Stool examination (direct smear or concentration procedures ) for trophozoites or cysts is useful. Duodenal aspiration may be necessary (more liable). Immunodiagnostic methods,5. Prevention and Treatment,Prevention depends on a high level of sanitation. Metronidazole is the recommended medicin

25、e.,Epidemic of Waterborne Giardiasis,Untreated or unfiltered water wilderness hikers & mountain streams Sewage contamination of water supply water/food contains cysts in feces “Traveler diarrhea”,Trichomonas vaginalis 阴道毛滴虫,Trophozoites in vaginal discharge swab, prostatic discharge or urine sedimen

26、t Trichomoniasis is a kind of sexually transmitted disease (STD) because its location in urogenital tract.,Trophozoite of Trichmonas vaginalis,attached to cervical/vaginal or prostatic/ urethral epithelium,Actively motile and moves by gliding motion,T. vaginalis infection Common cause of vaginitis worldwide Caused by interference of glyc