Protozoa

General Properties of protozoa Protozoa are one-celled animals with full vital functions. They may be freeliving or parasitic. Protozoa are minute parasites and can only be visualized under the microscope.

Basic structure Protozoa, the whole body consists of a singular cell. A protozoan cell is composed of : 1)plasma membrane 2)cytoplasm : a. ectoplasm(外质) b. endoplasm(内质) 3)nucleus ectoplasm(外质): The ectoplasm is the outer layer with function of protection, locomotion and sensation. endoplasm(内质): The endoplasm is the inner layer containing food vacuoles(食物泡) and cellular organelles (细胞器). It bears mitochondria (线粒体) , endoplasmic reticulum (内质网), Golgi apparatus (高尔基体) and so on. The endoplasm helps in nutrition and reproduction.

Life cycle patterns One-host form (direct) Two-host form (indirect) One stage form – Trophozoite Two stage form – Trophozoite & Cyst Two-host form (indirect) Mammals --- mammals Mammals --- insect vectors The life cycle of protozoa can be divided into two types.

Locomotion(运动): flagella(鞭毛) cilia(纤毛) pseudopodia(伪足).

Pathologic characteristics of protozoa 1. Multiplication (增殖) 2. Diffusion (disperse ) 3. Opportunistic pathogen (机会致病) Classification of protozoa: According their locomotion organelles, protozoa can be divided into four groups: Amoebae, flagellates, ciliates and sporozoan. protozoa reproduce in their host, when the number is enough, they may destroy the infected cells

Ecological Niches in the Human Body: 1. Skin: Leishmania 2. Eye: Acanthamoeba 3. Mouth: Amoebae and flagellates (usually non-pathogenic) 4.Gut: Giardia, Entamoeba (and invasion to liver), Cryptosporidium, Isospora, Balantidium 5. Genitourinary Tract : Trichomonas

Ecological Niches in the Human Body: 6. Bloodstream: Plasmodium, Trypanosoma 7. Spleen: Leishmania 8. Liver: Leishmania, Entamoeba 9. Muscle: Trypanosoma cruzi 10. central nervous system : Trypanosoma, Naegleria, Toxoplasma, Plasmodium

Medical Protozoa Pathogenic Opportunistic parasite Not normally pathogens Become pathogenic due to impairment of host resistance Clinical importance of the AIDS epidemic Opportunistic parasites 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

Pathogenic Intestinal Amoeba Entamoeba histolytica 溶组织内阿米巴

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

Entamoeba histolytica granular endoplasm ectoplasm Entamoeba histolytica

Morphology Trophozoite Size: 10-40 m Shape: ovoid with pseudopodium Basic structure: cytoplasm, vesicular nucleus (chromatin granules, nuclear membrane, karyosome)

E. histolytica trophozoite Ingested RBC endoplasm Nucleus with central karyosome and fine regular granules(peripheral chromatin granules), evenly distributed around the nuclear membrane Ectoplasm,Pseudopod E. histolytica trophozoite

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

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

E.histolytic cyst (schematic diagram) Spherical or round in shape, 10-20um in diameter, cyst wall 1-2 nuclei (immature cyst); 4 nuclei (mature cyst-infective stage). Glycogen vacuole food reservoir (brownish-yellow,iodine stained) chromatoid bodies with blunt, rounded ends in immature(young) cyst

E.histolytic cyst (schematic diagram) 4 ring-like nuclei with finely divided peripheral chromatin , glycogen vacuole and chromatoid bodies disappear Cyst wall and round shape Mature E. histolytica Cyst

E.histolytic cyst (under high power microscope)

E. histolytica Stages - CYSTS Infective Stage for humans The stage of discharge Diagnostic Stage in formed stools Resistant to external surroundings

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

The life cycle of E. histolytica is simple and is completed within a single host, which is human body Man got infected by ameba through ingestion of water and food contaminated with mature cysts. In the small intestine. the cyst became the trophozoites . The trophozoites grow and multiply by binary fission. They then colonise in the large intestine. Usually, the trophozoites never cause disease. As trophozoites pass down the digestive tract, trophozoites will turn into cysts again. Cyst is not infectious. However, when the man body's immune system is impaired or there are damages on the intestinal wall, the trophozoites may invade the tissue of the intestine and produce characteristic lesions in the colon. It will the be excreted in the feces

Life cycle The basic generation-cycle: cyst –trophozoites – cyst Trophozoites may invade intestine and spread Infective cysts and trophozoites pass in feces

Life Cycle 1 infective stage: mature cyst 2 access: mouth 3  ecological niches:  large intestine; liver, lung and other organs. 4  pathogenic stage:  trophozoite 5  diagnostic stage:  cyst; trophozoites

Pathogenesis Pathogenic factor Virulence Species: Immunity of host E.histolytica (pathogenic species) E.dispar (non-pathogenic species) Immunity of host Bacteria flora菌丛

Clinical Classification of Amebiasis (World Health Organization) Asymptomatic (intestinal) "Cyst Passers” Symptomatic Infection: Intestinal Amebiasis: (dysentery, colitis) Acute Dysenteric (dysentery) Chronic Non-Dysenteric (“self-cured”) Extra-Intestinal Amebiasis: Amebic Liver Abscess (ALA) Amebic Pulmonary Abscess Other sites (brain, skin, GU,)

Clinical classification Asymptomatic infection (carrier)  >90% (E. dispar?) Symptomatic cases <10% 8-10% dysentery, colitis, etc 2% invasive amoebiasis 0.1% deaths

Acute Dysenteric Amebiasis Symptoms: Bloody mucoid diarrhea RBCs and few WBCs in stools Abdominal pain weight loss Bloating(胃气涨), tenesmus(里急后 重) and cramps (痉挛)

Acute Dysenteric Amebiasis Signs: Fever (33%) Tender (enlarged) liver Stools positive for trophozoites +/- WBC NOT cysts in loose stools

Clinical manifestation Pinpoint lesion on mucous membrane Flask-shaped crateriform (volcano)ulcers

Chronic Non-Dysenteric Amebiasis “self-cured” carrier state Usually for 1 year, 37% symptomatic >5 years Intermittent diarrhea, mucus stool, abdominal pain, flatulence and/or weight loss E. histolytica trophs (rarely cysts) in stools Positive serology and ulcerations on sigmoidoscopy or pathology test

Amebic Liver Abscess (ALA) Extra-Intestinal Amebiasis Amebic Liver Abscess (ALA) Symptoms History of dysentery (1 yr), wt loss, abdominal pain, chest or shoulder pain Signs fever, hepatomegaly 肝肿大 Might find trophozoites in the aspirate Skin inflammation

Extra-intestinal amoebiasis Hepatic  (1) acute non-suppurative     (2) liver abscess: right upper quadrant pain, referred to the right shoulder. tender. Pulmonary Brain Skin, perianal infection Other extra-intestinal amoebiasis

Clinical manifestation

Clinical manifestation

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 amebic abscess of liver. Tube of "chocolate" pus from abscess. 

Diagnosis Pathogenic diagnosis Stool examination: Direct Fecal Smear (trophs and cysts) Fecal concentration and iodine dye techniques - (cysts) ZnSO4 or formalin-ether Cultivation DNA detection Sigmoidoscopy Serologic Tests (for chronic disease): ELISA, IHA (indirect hemagglutination) Imaging: X-ray; CT

Treatment of Amebiasis For invasive forms: metronidazole For luminal forms: Iodoquinofonum, paromomycin, diloxanide Do not treat asymptomatic intestinal E. dispar infection

Epidemiology Cosmopolitan世界性的/worldwide China: 3%~10%; Rural area>urban Source of infection: carriers Transmit route: water contamination Insects: fly, cockroaches

Prevention & Control Individual measures Diagnosis and treatment of E. histolytica patients no animal reservoirs (other than humans) are known Safe drinking water (boiling or 0.22 µm filtration) Cleaning of uncooked fruits and vegetables Prevention of contamination of foods Personal hygienic health education

E.coli cyst (under high power microscope)

trophozoite cyst nucleus E.h E.c

Question 1.How to diagnose hepatic amebiasis? 2.What are the transmission route of E. histolytica ? 3.Who should be treated for amebic infection?

Giardia lamblia It is a pathogen of digestive tract.

Morphology of Giardia lamblia trophozoite looks like monkey face adhere to surface of intestinal cell Median body

Trophozoite of Giardia lamblia (under electron microscope)

Trophozoite of Giardia lamblia (under high power microscope, stained film)

Cyst of Giardia lamblia Oval-shape,4 nuclei , flagella and axostyle can be seen Cyst wall

Giardia lamblia life cycle

Life Cycle: One host two-stage life pattern. trophozoites – cyst The infective stage is the cyst with four nuclei. The cysts are passed out in the feces and ingested in contaminated water and food. Dogs, monkeys and beavers can also be infected , and sometimes may be a source of human infection. Inhabit the duodenum, upper jejunum.

Pathogenesis: The attachment of G.l to the intestinal mucosa may produce a low grade catarrhal inflammation & that their mechanical & toxic action may interfere with the absorption of Vit.A & fats.

Cause Giardiasis. Children>Adults. Symptoms ranging from mild diarrhea, flatulence, anorexia, cramp-like abdominal pains & epigastric tenderness etc. leading to the intestinal malabsorption syndrome. Biliary disease (Cholecystitis), particularly in adults.

Laboratory diagnosis: Finding cysts in formed stools, trophozoites & cysts in diarrhetic feces. Concentration methods increase the chances of detection. The duodenal content gives a higher percentage of positive findings.

Treatment & Prevention: The drug of choice is quinacrine hydrochloride or metronidazole. Pay attention to personal hygiene.