طفيليات نظريثالث طب 4 / 10 / 2016 *
د. زينب خالد خليل Lec. 1 *Parasitology Is a science, study the relationship between two organisms one called parasite & the other is called the host .
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CLASSIFICATION OF PARASITES: Parasitic kingdom include three phyla
1- Protozoa. 2- Helminthes. 3- Arthropods.*
I- Protozoa : Is a phylum of the animal kingdom consisting of unicellular parasites, divided into 4 classes according to the organ of locomotion: 1- Class sarcodina: Parasites that move by means of pseudopodia example Entamoeba histolytica. 2-Class mastigophora : Parasites that move by means of flagella example Giardia lamblia
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3- Class ciliates : parasites that move by means of cilia example Balantidium coli . 4- Class Sporozoa : parasites have both sexual and asexual reproductive organs, all these parasites are intracellular and they have no organ of locomotion example Plasmodium parasites causing malaria.
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II- Helminthes : They are metazoa ( Multicellular parasite ) wormlike parasite, divided into 3 classes :
1.Class Nematoda ( Roundworms ) : Example: Intestinal nematodes, Ascaris and Entrobius .
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2 -Class Cestoda ( Tapeworms) : They are flattened and segmented worms, e.g: Taenia spp and Echinococcus . 3- Class Trematoda (Flukes): They are flattened leaf- shaped worms. e.g: blood flukes.
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III- Arthropods : These parasites having exoskeleton and jointed legs, divided into 2 classes: 1- Class Insecta :e.g. Mosquitoes, housefly. 2- Class Arachnida :e.g. Ticks and mites .
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GENERAL TERMINOLOGY: * Pathogenic parasite : A parasite infect the host and cause tissue changes or a disease (harmful parasite). * Commensal parasite : A parasite that when infect host gets benefit but the host neither benefited nor injured .
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* Ectoparasite: A parasite present on or in the exterior surface of a host. * Endoparasite: A parasite present within the body of its host .
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Facultative parasite: A parasite capable of living an independent or a parasitic existence .
Obligatory parasite: A parasite is capable of living as parasitic on a host, but it can not exist as independent living.
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Types of hosts *Definitive host: The animal or human in which a parasite passes its adult stage and/ or the sexual reproductive phase can take place. *Reservoir host: An animal e.g. (dogs,cats or rodents) which carry a species of parasite from which man become infected. The host do not get the disease or its carried as a subclinical infection.
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* Carrier:. A host carring a parasite but not showing any clinical sings or symptoms.
* Accidental ( or incidental ) host : Infection of a host other than the normal host species.*
Vector: Any arthropod or other living carrier which transport a pathogenic micro-organism from an infected to a non infected host. A vector may transmit disease : (1)passively called (mechanical vector) e.g.housefly (2) The vector is essential in the life cycle of the pathogenic parasites called (biologic vector) e.g.mosqutoes.
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Ectoplasm: The gelatinous material beneath the cell membrane . *Endoplasm: The fluid & inner material of a protozoal parasite .
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*Flagellum(flagella) : An extension of ectoplasim which provides locomotion similar to a tail .
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Pseudopod:A protoplasmic extension on the trophozoites of amoeba allowing them to move and engulf food .
Cilia: Hair like processes attached to a free surface of a cell; function for motility of the cell, e.g. Balantidium coli .
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د. زينب خالد خليل Lec.(2) Amoeba *
Amoebas: The genus Entamoeba include many species that infect humans, but not all of them are associated with disease like E. histolytica which is a pathogenic amoeba causing intestinal and extraintestinal Infections.*
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Morphology ( Trophozoite ): 1- Its size (12-30 µm), Clear ectoplasm . 2- Large finger – like pseudopodia 3- The endoplasm is granular and may contain RBCs.4- It has one nucleus, contain small central karyosome and fine chromatin granules arranged regularly beneath nuclear membrane. *
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Morphology ( mature cyst) : 1- Small (10 – 20 µm) , spherical in shape, smaller than that of E. coli, containing 1 - 4 nuclei is usually found in feces . Each nucleus contain similar nuclear morphology like the trophozoite. *
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cyst
trophozoite*
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Epidemiology : . * The incidence of Amebiasis is common & high in tropical & subtropical areas especially in areas of lower socioeconomic status due to: poor sanitation(2) overcrowding & (3)malnutrition It is estimated that up to 10% of the world`s population may infected with E.histolytica.
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Transmision of amoebiasis occur through: 1. Mature cyst is the main sours of the infection which passes with the feces of chronic patients or asymptomatic carrier . 2. Human being acquire the infection via contamination of food, drinks, vegetables or hands with infective cysts especially in resturants . 3. Flies (House fly) play an important roles in transmission of these cysts to the food of human .
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Pathogenesis of E.histolytica: The Pathogenic activity of E. histolytica depend upon :
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1- The resistance of the host . 2- The number of the amebas. 3- Presence of pathogenic bacteria. 4.Presence of physical & chemical injury of the mucosa .
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The lesions produced by E. histolytica are primarily in large intestine and seconderily extraintestinal especially the liver, brain or any organ of the body may be affected .
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Pathogenesis of Intestinal lesion : 1.The lesion vary from small ulcer to a large typical flask shape ulcer. 2.The ulcer has a wide base and narrow opening with irregular elevated edges . 3.The ulcer characterized with large area of tissue necrosis, cell infiltration & rapid lysis of inflamatory cells. 4.The amoebas usually found on the floor of the base of ulcer.
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E. histolytica in the large intestine ( Flask shape ulcer )
*Clinical features of intestinal lesion : 1- The incubation period range from 2 – 4 weeks . 2- The majority of infections with E.histolytica show no symptoms or show symptoms which varies from mild to intense and long lasting . *
The typical symptoms include : 1- Diarrhea, The diarrhea frequently alternates with constipation or soft stools may contain mucous but no visible blood . 2-Abdominal cramps. 3-Nausia. 4-Anoroxia.
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5- Dysentery : Which is usually starts slowly with abdominal cramps and associated with loose stools and diarrhea with blood , mucus and necrotic tissues.
6- Few patients especially children may show fever, vomiting, abdominal tenderness .
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The complications of intestinal amoebiasis: 1- Appendicitis . 2- Intestinal perforation . 3- Hemorrhage . 4- Liver abscess. 5- Ameboma (Granulomas) : a. Are a painful abdominal mass which occur most frequently in the caecum and assending colon .
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b. This lesion may be confused with carcinomas or tumor . c.Obstructive symptoms or dysentery may also be associated with ameboma.
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Extraintestinal Amoebiasis : 1.The metastasis of amoeba usually via blood strem or by direct extension after intestinal perforation to the peritonium. The amoeba may cause local abcses or peritonitis or migrate to the liver which is the most commonly affected than other organs e.g, lungs, perianal skin or brain.
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Extraintestinal Amebiasis
*2.Amoebic liver abscesses: Are the most common extraintestinal amebiasis and charactarised By: a.Hepatomegaly, Liver tenderness, fever and anorexia . b. Liver function tests are usually normal or slightly abnormal . c. Liver abscesses will occasionally rupture into the peritoneum causing peritonitis
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3.Pulmonery amoebiasis : a. This infection due to the direct extension of the liver abscess through the diaphragm, or via blood. b.The clinical symptoms are: cough, chest pain, dyspnea and fever . c.The sputum may be purulent or contain blood and trophozoites of E. histolytica.
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4. Cutaneous amoebiasis : It is caused by contact of the skin with amoebic abscess which lead to fistula in the skin.
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Diagnosis of Amoebiasis : 1- Stool of patient should be examined microscopically : a- The typical amoebic stool is contain blood, mucous , few WBC & Bacteria . b-Direct method with saline for motile trophozoite . C-Stool specimens should be stained usually with ioden and microscopically examined for cysts of E.histolytica .
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2- Culture of stool. 3- Sigmoidoscopy may reveal the charecteristic flask-shaped ulcers especially in sever cases .
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4- Biopsy & fluid from large intestine aspirates also be examined microscopically for trophozoites . 5- Serology, is very important for the diagnosis of extraintestinal amoebiasis e.g: Indirect haemagglutination (IHA) & Polymerase Chain Reaction (PCR test) .
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6- Ultrasound, CTscan, MRI can be used to detect hepatic abscesses .
*Treatment : 1. A symptomatic (source of infection) patients can be treated with Diiodohydroxyquine with tetracycline.
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Treatment Cont… : 2. Symptomatic patients with diarrhea or dysentry or extraintesinal amebiasis should be treated as follows : a- Patients should remain in bed and receive a high protein and high vitamin with adequate fluids . *
b. Chemotherapy for sever amoebiasis: 1.Metronidazol (Flagel) is the drug of choice : 750 mg three times a day, orally for 5 – 10 day. 2.Tetracycline & diiodohydroxyquine are recommended to be given to the patient since metronidzal may not always cure the intestinal infection . *
Prevention & Control : 1- All human infections should be treated 2- A symptomatic carriers should be treated especially those working in resturants .
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3- Effective environmental sanitation is necessary to prevent water ,food , and vegitable contamination, e.g. Sewage disposal should be treated with chemical before used as fertilizer in gardens. 4- Chlorination & filtered water supply are important to kill the cyst of E.histolytica.
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5- Insects should be controlled by insecticides. 6- Uncooked vegetables should be washed with running water. .
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د. زينب خالد خليل Lec.(3). NON PATHOGENIC AMOEBA *
None pathogenic amoeba : These parasites are commensals none pathogenic but they are important because they may be confused with E. histolytica in diagnostic investigations. These amoebas include many free-living and parasitic amoebas. The most amoebas affecting human being are:
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1- E.coli. 2- E.gingivalis . 3- Dientamoeba fraglis. 4- Endolimax nana . 5- Iodoamoeba butschlii . 6- Other amoebas infecting human are morphologically very simillar to E.histolytica, e.g, E.hartmanni and E.dispar.
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7- Free living amoebas are Negleria & Acanthamoeba are accidental parasites of human being .The majority of these amoeba are non-pathogenic commensal parasites or only cause mild infection.
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2. The ectoplasm is not clear and it has small pseudopodia. 3. It has one nucleus contain large eccentric karyosome, and large chromatin granules arranged irregularly beneath nuclear membrane. The cyst : is large oval in shape , 10 – 30 µm and it has 1 - 8 nuclii, the characters just like that of trophozoite. *
Amoebas Amebas include many free-living and parasitic amebas.The most important species which parasites human being are : 1- Entamoeba histolytica. 2- E.coli. 3- E.gingivalis . 4- Dientamoeba fraglis. 5- Endolimax nana . 6- Iodoamoeba butschlii . 7- Other amoebas infecting human are morphologically very simillar to E.histolytica, e.g, E.hartmanni , E.dispar. & E.polecki . 8- Free living amoebas are Negleria & Acanthameba are accidental parasites of human being . The majority of these amoeba are non-pathogenic commensal parasites, or only cause mild disease. E.histolytica can cause sever infection & can become a highly virulent and invasive parasite that causes a lethal systemic disease . So the identification of E.histolytica requires differentiation from other parasites wich are mentioned above.
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2. The ectoplasm is not clear. and it has small pseudopodia. 3. It has one nucleous contain large eccentric kariosome, and large chromatin granules arrenged irregularly beneath nuclear membrane. The cyst is large oval in shape and it has 8 nucleous, the characters just like that of trophozoite.
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Lec.(4) د. زينب خالد خليل Balantidium coli *
*Primarily a zoonotic intestinal parasite: animals that represent a source of infection include Horses, cows, pigs The most risky people are farm workers Symptoms similar to amoebiasis except, No extraintestinal infection
Balantidium coli
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Balantidium is the largest protozoan and only ciliate known to parasitize humans
Morphology*
Trophozoite morphology
50-150 mic Cilliated parasite Oval shape Greenish yellow color Kidney or bean shape Macronucleus Small micronucleus Retractile food vacule*
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Cyst morphology
45-55 mic Spherical shape Cyst wall is thick consist of 1-2 layers No phagosome Macronucleus Conractile vacules No cilia*
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Life cycle & Pathogenicity:
Infection is happened by consumption of material contaminated with feces of some farm animals cotaining cyst (the infective stage). Exyst ation occare in the small intestine releasing trophozoites that migrate to the large intestine. Trophozoites reside in the lumen of large intestine Invade mucosa and submucosa. Feed on mucosal cells, RBC, leukocyte where they divide by transverse binary fission. Encystation is triggered by dehydration of intestinal content.*
Life cycle
*Habitate
*Parasite live in L.I specially cecal region *Cyst formed in large intestine or in outer environment*
Clinical signs and symptoms
Intermittent periods of diarrhea and constipation Bloody diarrhea Abdominal pain anorexia Ulceration of large intestine Tender colon Cachexia Gangrenous lesions could occur*
1.History: if there any animal contact. 2.Symptoms Clinical signs could confused by E. histolytica infection 3. Laboratory tests: finding the typical trophozoites and cysts in the stool
Diagnosis
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Diagnosis cont….. Laboratory methods to detect (cyst or trophozoite) in stool by Direct wet mount preparation method Stained smear by iodin Looking for characteristic kidney shape nucleus and retractile food vacule
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Prevention & control
Avoid ingestion of food and drinks contaminated .by animal feces*
Treatment
1.Tetracycline 2.Iodoquinol 3.Metronidazole*