醫(yī)學(xué)寄生蟲學(xué)課件：3Protozoa

1、Single celled microorganisms belonging to the animal kingdom are classified as Protozoa Within its single cell, it contains all structures required for performing its completed functions, for example moving, digestion, excretion, respirationreproduction Protozoa ProtozoaFlagellapseudopodaciliumProto

2、zoa basic structure comprise a nucleus & cytoplasmThe nucleus is usually single, but may be double or multiple The nucleus contains one or more karyosomeThe chromatin may be distributed along the inner surface of the nuclear membrane (peripheral chromatin) or as compress masses around the karyos

3、omeThe cytoplasm consists of an ectoplasm & endoplasmIt means the cytoplasm can often be differentiated into an outer rim of glasslike ectoplasm and a more granular inner endoplasmectoplasmectoplasmectoplasmendoplasmProtozoa show a wide range of size, shape and structure, yet all possess certain

4、 essential character and function2-3 m to 100 mtoProtozoa exist in two main forms: the trophozoite which is the active, invasive stageIt could be active feeding and growing, they may obtain nourishment from environment by diffusion or by active transport across the plasma membraneLarger food particl

5、es are taken in by phagocytosis through pseudopodiaSome species ingest food through special month-like structures or cytostomesMinute droplets of food may also enter by pinocytosisThe cyst is the resistant stage that can survive un-favourable conditionCystic stage enable prolonged survival under un-

6、favourable conditionsCyst could be reproduction by the nucleus dividing once or moreCyst usually the infective stage for the host Reproduction of protozoa may be asexual through binary fission or multiple fissionThe most common method is binary fission by mitotic division of the nucleus, followed by

7、 division of the cytoplasm The nucleus undergoes several successive divisions within the schizont to produce a large number of merozoitesReproduction is usually asexual The sexual reproduction through conjugation or gametogony Sexual stage are seen in sporozoa, and male gametocytes and female gameto

8、cytes are produced, then form the zygote, them produce to numerous sporozoites by sporogony Protozoa must be transmitted from one host to another for its surviveThis is achieved by either transforming in to cyst stage or by changing their method of reproduction from asexual to sexual, e.g.in malaria

9、 parasite, the sexual cycle or gametogony takes place in the mosquito and the asexual cycle or schizogony take place in manThis process is known as alternation of generation Some free-living protozoa located in containing green plastids that enable them to perform photosynthesis, in all habitations-

10、in water, in hot spring, in ice, under the soil, in snow, on top of Mt. and so on but sometime ClassificationSubject to much variation Four major types of organisms will be discussedFlagellated protozoa MastigophoraAmoeba pseudopodaCiliophoraSporozoaParastic protozoa have adapted to different host,

11、with more restricted physicochemical requirementsoral cavityintestinalvaginaBlood-& Tissue- DwellingprotozoaLumen-DwellingprotozoabloodlymphaticsmacrophageserythrocytesCentral nervous system 1. Skin: Leishmania 2. Eye: Acanthamoeba 3. Mouth: Amoebae and flagellates (usually non-pathogenic) 4.Gut

12、: Giardia, Entamoeba (and invasion to liver), Cryptosporidium, Isospora, Balantidium 5. vagina: Trichomonas 6. Blood: Plasmodium, Trypanosoma 7. Spleen: Leishmania 8. Liver: Leishmania, Entamoeba 9. Muscle: Trypanosoma cruzi 10. CNS: Trypanosoma, Naegleria, Toxoplasma, Plasmodiumroute of entry into

13、host is one of most important aspectsprevention of infection requires knowledge of transmission cycleOral route via cysts: parasite stage facilitates dispersal in the environment & enables dormant environmental stage dormancy for months to years many intestinal protozoa produce resistant cysts(E

14、ntamoeba, Cryptosporidium & Giardia) Bloodsucking vector bite: tsetse fly ,sand fly & mosquitoes organisms injected into host bloodstream or tissuesundergo complex developmental lifecycles mosquitoes transmit malaria (Plasmodium) tsetse flies transmit African sleeping sickness Sexual infecti

15、on: parasites rely on human activity for dispersal (Trichomonas vaginalis is sexually transmitted)Protozoa: Mechanisms of Entry consequence of infection is tissue damage extent of cellular damage by a given parasite related to: location of its niche (the brain is a bad place for an infection)metabol

16、ic requirements of parasite population density throughout infectionenergy is derived from host places a burden on infected hosts destruction of cells & tissuesPlasmodium (malaria) parasites rupture red cellsEntamoeba histolytica ingests living cells Toxoplasma destroys many cell typesimmune resp

17、onse may also damage tissuesProtozoan： Mechanisms of PathogenesisDiagnosis and TreatmentFinding parasites in blood, bone marrow, cerebrospinal fluid(CSF) or stool is diagnosticXenodiagnosis is where laboratory reared bugs are allowed to feed on patients and then after a period of time they are exami

18、ned for flagellatesDrug-resistant？Entamoeba histolytica: a protozoan parasite, cause amebiasisFifty million people worldwide suffer from E. histolytica infection amebic dysentery and amebic liver abscess kill at least 40000-110000 individuals yearlythe second leading cause of death among parasitic d

19、iseases Entamoeba histolytica, a protozoan parasite, cause amebiasis, and a variety of clinical manifestations, from asymptomatic to colitis or extraintestinal abscess. E. histolytica has been reclassified into two species, Entamoeba histolytica Schaudinn 1903, and Entamoeba dispar Brumpt,1925, on t

20、he basis of biochemical, immunologically, and genetic findings. Entamoeba histolytica The two species are monphologically inseparable, but only E. histolytica is responsible for invasive amebiasisAmebiasis is estimated by World Health Organization to be the second leading cause of death among parasi

21、tic diseases worldwideThe life cycle of E. histolytica has three stages; trophozoite, precyst and cyst. Trophozoite vary in size from 10 to 60 mhighly motile, with a pleomorphic shape. Organisms recovered from diarrheicor dysenteric stools are generally larger than those in a formed stool from an as

22、ymptomatic. MorphologyEntamoeba histolytica Schaudinn, 1903Cyst Precycst the trophozoites of E. histolytica maycondense into a round mass( precyst),and a thin wall is secreted around the immature cyst. Cyst there are two type of inclusions within such immature cyst, a glycogen mass and highly refrra

23、ctile chromatoidal bar with smooth, rounded edges there is nuclear division with the production of four nuclei in mature cyst, the cysts range in size from 10 to 20 m. the cyst matures, the glycogen completely disappears; the chromatoidal may also be absent in the mature cyst. the quadrinuclested cy

24、sts are the infectious agents. Life cycleHuman being is the only susceptible hostThe mature cyst is the infective stageThe developmental stage of E.histolytica include a cyst, a trophozoite, and a transitional form-the precyst.Transmission occurs via contaminated food or water, fingersThe infective

25、cyst form of the parasite survives passage rough the stomach and small intestines trophozitetrophozite cyst metastasisliver, lung, brainQuadrinucleate CysttrophoziteInhabits in large intestineLarge intestine ulcersLung abscessLive abscessLung abscessBrain abscesstrophozitestrophozites cyst trophozit

26、esmetastasis Cysts orQuadrinucleate CystsPathogenesis & SymptomsPathogenesis ingestion of the quadrinucleate cyst of E. histolytica from fecally contaminated food or water initiates infection infection also occurs through direct person-to- person contact inhabits the large intestine, invade the

27、mucosal crypts, feed RBCs & form ulcersPathogenic factors: Lectin adherence to host cells, signal, amoebapores form pores in host cell membranecysteine proteinases: cytopathic for host tissue cell killing phagocytosis invasion Ameba1. Adherence3. Cell killing4. Phagocytosisand Invasion2. Lect-in

28、 Signal amoebic invasion through the mucosa and into the submucosal tissues is the hallmark of amoebic colitis the lateral extension through the submucosal tissues gives rise to the classic flask-shaped ulcer of amoebiasis or ameboma amebic liver abscess is the most common manifestation of extrainte

29、stinal disease the most serious complication of amoebic liver abscess are rupture Sites affected in AmoebiasisSymptoms asymptomatic/Carrier state: the amoebae may reproduce but the patient shows no clinical symptoms symptomatic intestinal amebiasis: may complain of more specific symptoms, including

30、diarrhea, abdominal pain and chronic weight loss symptomatic extraintestinal amebiasis: the formation of an abscess in the right lobe of the liver , trophozoites extension through the diaphragm, causing amebic pneumonitis (abscess) and/or brain abscess Abscess pus ABCLesion near perineumFlat bone Am

31、oebiasis, courses of infectionCT scan showing a mass in right lung lobe with multiple nodules and pleural effusion: (A) CT scan of right-middle lung lobe (2013/5/13); (B) CT scan of right-low lung lobe (2013/5/13). CT scan showed a slowly progression on pulmonary mass and nodules: (C) CT scan of rig

32、ht-middle lung lobe (2013/10/10); (D) CT scan of right-low lung lobe (2013/10/10). CT, computed tomography. (A) (B)Microscopic examination of the sediments section of pleural effusion revealed amebic trophozoites (H&E stain, A 200, B 400). (C)Amebic trophozoites (thick arrow ) and macrophages (t

33、hin arrow) were found in the liquid-based sputum section (H&E stain, 200). (D) Adenocarcinoma cells were detected by liquid-based sputum cytology (H&E stain, 200). Diagnosis Microscopic examination a direct saline wet mount-trophozoites, cyst from pus- trophozoites only iodine stain-cyst con

34、centration techniques permanent stained E.histolytica E. coli size 10-40 m 20-50 m Trophozoite pseudopodium more transparent less transparent movement active sluggish inclusion RBC no RBC karyosome centrol, small asymmetrical size 12-20 m 15-25m Cyst No. of nuclei 1-4 1-8 chromatoid rounded ends spl

35、intered endsEntamoeba histolytica Schaudinn, 1903Entamoeba dispar Brumpt, 1925Entamoeba nuttalli Castellani, 1908Immunologic techniques monoclonal antibody detected antigen from stool or pus detected specific antibodies by antigen ELISA, IFA, IHA differential diagnosis: ulcerative colitis and crohns

36、 disease 16 64 256 1024 409616 64 64 256 1024Neg. contPos. contSampleAntibody titer1:64 positiveTriage Parasite Panel, combination with G. lamblia, C. parvum, and E. histolytica/E. dispar PCR techniques 18S rRNA, Prx gene differentiation of E.histolytica from the commensals E. dispar is not possible

37、 by morphology but requires the use of species-specific Mab or PCR techniquesImaging colonoscopy, Sigmoidoscopic examination -biopsy sonography, computed tomography (CT), magnetic resonance imaging (MRI)Epidemiology generally higher in the tropics, subtropics, and poor sanitation, poor nutrition (fo

38、r example) a high-carbohydrate diet, alcoholism, genetic makeup, bacteria infection of the intestine, local injury to the colonic mucosa the true prevalence of E. histolytica is perhaps closer to 1% to 5% worldwideEpidemiology generally higher in the tropics, subtropics, and poor sanitation, poor nu

39、trition (for example) a high-carbohydrate diet, alcoholism, genetic makeup, bacteria infection of the intestine, local injury to the colonic mucosa the true prevalence of E. histolytica is perhaps closer to 1% to 5% worldwide the realization that E. histolytica, E.dispar & E. nuttalli are morpho

40、logically identical species with remarkable different physiological and pathetical characteristics has impacted on all aspects but notably on the epidemiology no sexual preference for intestinal amoebiasis, but amebic liver abscess is 3 to 10 times more common in men the high-risk group for amoebias

41、is include travelers, institutionalized mental patients, promiscuous homonsexual a severe form of infection in neonates, pregnant women, women in the postpartum period, immunocompromised patients, patients with malnutrition ingestion of the infective cyst, through hand mouth contamination & food

42、 /water contamination flies & cockroaches may also serve as vectors of E. histolytica, contamination of foodstaffsTreatment & Prevention Whenever possible, a laboratory diagnosis of E.histolyticainfection, unless confirmed by visualization of ingested RBCsin the trophozoite, should be substa

43、ntiated by (1) presence of RBCs in stool (2) serum antibody titer (3) stool E.histolytica antigen titerInfection Drug and DosageAsymptomatic intestinal paromomycin 25-30mg/kg/D in 3 amoebiasis divided does for 7 days metronidazole 750 mg 3 time daily for 10 daysAmebic dysentery and liver abscess met

44、ronidazole 750 mg 3 time daily Ameboma for 10 days follow by paromomycinMetronidazole and tinidazole are first-line agents in the treatment of acute amebic colitis and amebic liver abscess therapeutic aspiration of an amebic liver abscess is occasionally required as an adjunct to antiparasitic thera

45、py the prevention of amebic infection starts with avoidance of fecal contaminated food and water. The high incidence of amebiasis in recent community-based studies suggests that an effective vaccine would improve public health. Free-living amoebae - Naegleria, Acanthamoeba, BalamuthiaHuman beings us

46、ually acquire Naegleria infection from swimming in the contaminated water or contaminated pipelineNaegleria fowleri caused primary amebic meningoencephalitis (PAM), an acute, suppurative infection of the brain and meninges. This ameba is responsible for over 200 cases world wideNaegleriaAcanthamoeba

47、 species cause granulomatous amebic encephalitis (GAE), amebic keratitis, corneal ulceration, amebic dermatitis Balamuthia infection have cutaneous lesions and GAEAcanthamoeba, BalamuthiaAt least 5 species of Acanthamoeba have been identified in human tissues.Free-living trophozoites and cysts occur

48、 in both the soil and freshwater.Trophozoites occur only as ameboid forms:A new freshwater ameba called Balamuthia has been incriminated, about 80 cases of amebic meningoencephalitis in humans since 2001. only 2 survivals easily misidentified so some of the cases of granulomatous amebic meningoencep

49、halitis caused by Acanthamoeba may well have been caused by BalamuthiaIn vivo confocal microscopy a wet mount of cerebrospinal fluid (CSF) is usually more useful detection of motile organisms is a diagnostic finding, but they must distinguished from motile leukocytes to detected of parasites a cultu

50、re is in order DNA-based or Mab-based technique may also help for difference diagnosis In vivo confocal microscopy (IVCM) the drug of choice for the treatment of PAM is amphotericin B the treatment of GAE has not been standardized the treatment of AK includes systemic antifungal drugs, tropical anti

51、amebic eye drops, and surgical debridement of the ocular lesions (Corneal epithelial scrape) Cornea transplant Cornea transplantCorneal epithelial scrapeGiardia lamblia Trophozoites of Giardia are fund in the upper part of the small intestine ( duodenum), gallbladder, causing giardiasis or tourist d

52、iarrhea, also opportunistic parasitic disease Giardia is worldwide in distribution Giardia lamblia is considered to be one of the major cause of parasitic diarrhea Human infection mainly results from ingestion mature cyst-contaminated food or water Parameter Typical Characteristics Size range 8-20m

53、long, 5-16m wideShape Pear-shape, teardrop Nuclei Two ovoid-shaped, each with a large karysome Flagella Four pairs, anterior posterior centrallateral Others Two median bodiesSucking disc Parameter Typical Characteristics Size range 8-17m long, 6-10m wideShape Ovoid Nuclei IM cyst-two M cyst-four, ea

54、ch with a central karysome Cytoplasm Retracted from cell wall Others Two median bodies in IM cyst or four in M cyst2 trophozoites released per cystMultiply by binary fission every 12 hrsSucking disc used for attachmentCyst forms transit to colon excystation occurs in the upper regions of the small i

55、ntestine, where the trophozoite resides & multiplies by binary fission trophozoites pass through the digestive tract, encyst in the colon & transformed into cysts, pass in the feces cysts with highly resistantNormal villi of small intestine. Flattened, fused villi from patient with G. lambli

56、a. PathogenicityInfections with G. lamblia are often completely asymptomaticParasites attack the fuzzy coat of microvilli Extensive ulceration of mucosa may occur in heavy infection Symptomatic infection may cause intestinal disorders, most commonly diarrhea-Vit A & soluble fat, nausea, flatulen

57、ce, weight loss, mal-absorptionOccasionally, bile duct & gallbladder involvement may produce jaundice & colic Infections with G. lamblia are often completely asymptomatic a direct saline wet mount-trophozoites, cyst iodine stain-cyst concentration techniques Examination of multiple samples i

58、s recommended prior to reporting that a patient is free of Giardia. DUODENAL ASPIRATION entero test -an alternative & more satisfactory technique for trophozoites detection 90 cm line for children 20 cm silicon rubber- covered thread and the others soft nylon yarn 140 cm line for adultsAntibody

59、detection ? DNA-based or Mab-based technique may also help for difference diagnosis common in children 6-10 years of age, with a high incidence among tourists and homosexual male, opportunistic protozoa (parasite) Metronidazole is most common drug in treatment (Tinidazole， Paromomycin) Trichomonas v

60、aginalisT. vaginalis occurs only as the trophozite, there being no cystic form in Trichomonas , pseudocyst forms was reported while the normal pH of the vagina is 3.8 to 4.4, when the level of acidity is disturbed, an environment is created in which T. vaginalis growthinfants will been infected through the birth canal / during vaginal deliverytreatment of choice for T. vaginalis infectio