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Nursing college, Second stage Microbiology Dr.Nada Khazal K. Hendi L12: Parasitology Parasitology: is the science dealing with the study of protozoa & pathogenic effects. Parasite: an organism that live in or on anther organisms (host)and obtains its food from host. Host: an organism which harbors parasite. The parasites of medical importance fall into kingdom: Protista and animalia. The parasites are classified as three phyla into 1. phylum: protozoa 2. phylum: platyhelminthus 3. phylum: nematoda Protozoa is single organism microscopic (belong to Protista ). In contrast, Helminthes are multicellular organism or worm, macroscopic (belong to animalia). It possessing well differentiated tissues &organ system. The length of worm vary from less than millimeter to more than meter. Classes of Protozoa: Type of locomotion of organelle have been used to divide these into four major classes: 1. Rhizopods (amoebae): organelle of locomotion are pseudopodia and the mode of reproduce by binary fission. Such as E. histolytica 2. Ciliaphora: organelle of locomotion are cilia and the mode of reproduce by binary fission. Such as Blantidium coli 3. Mastigophora or flagellated : organelle of locomotion are flagella and the mode of reproduce by binary fission. 4. Sporozoa: is non motile and reproduce by sporogony\schizogony. The types of relationships between parasites and host 1. Phoresis: the parasite transport through the host with mechanism. E. histolytica 2. Commensalism: this relation positive for parasite while neutralized for host. 3. Mutalism: positive for parasite and host. 4. Parasitism: positive for parasite and negative for host. 1 Microbiology Nursing college, Second stage Dr.Nada Khazal K. Hendi The infected phases of parasites: 1. ovum. 2. larva. 3. cyst. 4. adult phase (worm). Transmission of parasitic infection 1. modes or portals of entry the host: ingestion, inoculation, inhalation, congenital, venereal, and other. 2. portals of exit from host: respiratory tract, gastrointestinal tract, genital tract, biting insect, and allergy. 1. Class: Rhizopods (amoebae): Entamoeba histolytica& Entamoeba coli Morphology E. histolytica & E. coli living in intestinal.The live cycle consists of two stage: trophozoite & cyst. The morphology of cyst & troph. of E. histolytica& E. coli as shown in following table. a protozoa, that infects predominantly humans and other mammals such as dogs and cats can become infected (the environmental survival form of the organism) with their feces. The active (trophozoite) stage exists only in the host and in fresh feces; cysts survive outside the host in water and soils and on foods, especially under moist conditions on the latter. When swallowed they cause infections by excysting (to the troph. stage) in the digestive tract. Amebiasis (or amoebiasis) or amebic dysentery is the name of the infection caused by E. histolytica. In addition to infection of the large intestine , the organism may invade other internal organ such as the lung , liver, skin and brain. signs and symptoms AMEBIC DYSENTERY: In severe cases of intestinal amebiasis, the organism invades the lining of the intestine, producing sores (ulcers), bloody diarrhea, severe abdominal cramps, vomiting, chills, and fevers as high (40°C). In addition, a case of acute amebic dysentery may cause complications, including inflammation of the appendix, a tear in the intestinal wall (perforation), or a sudden, severe inflammation of the colon (fulminating colitis). 2 Nursing college, Second stage Microbiology Dr.Nada Khazal K. Hendi Entamoeba coli is a non-pathogenic amoeba with world wide distribution. Its life cycle is similar to that of E. histolytica but it does not have an invasive stage and does not ingest red blood cells. Laboratory diagnosis of amebiasis is made by stool examination. the diagnostic stages are troph. Or cyst or both in diarrhea stool. The infective stage is cyst. Table showing the comparison between trophozoite of E. histolytica& E. coli characteristic Size No. of nuclei Karyosome Peripheral chromatin Cytoplasm Cytoplasmic inclusion Motility Troph. of E. histolytica Troph. of E. coli 8-65µm One Small& centeral Fine& evenly distributed Finely granular 12-55µm one Large irregular shape, eccentric Coarse& unevenly distributed Coarse& often vacuolated Ingested RBC Bacteria, other debris Progressive, finger like pseudopodia Non Progressive, blunt pseudopodia Table showing the comparison between cyst & of E. histolytica& E. coli characteristic Size shape No. of nuclei Karyosome Peripheral chromatin Cytoplasm Cytoplasmic inclusion cyst of E. histolytica 8-22µm Spherical to round One to four Small& centeral Fine& evenly distributed Finely granular Chromatoid bars, rounded ends, diffuse glycogen mass cyst of E. coli 8-35µm Spherical to round One to eight Large irregular shape, eccentric Coarse granular Chromatoid bars, rounded with pointed ends, diffuse glycogen mass 2. Class: Ciliaphora: Blantidium coli B. coli has two types of nuclei: macronucleus that responsible for all activities of parasite except the reproduction, while micronucleus that responsible for the reproduction only. B. coli live in digestive system. It cause blantidiasis similar ameobiasis but differ from E. histolytica that invase the liver. It have two phase: troph. & cyst. 3 Nursing college, Second stage Microbiology Dr.Nada Khazal K. Hendi 1. Troph.: found in large intestine is consider largest parasite of protozoa, ovule shape, covered with equal long cilia have two nuclei macronucleus (kidney shape) & micronucleus (vascular shape). It have two contracted vacuoles & many vacuoles contain bacteria or RBC in the acute infection with this parasite. 2. Cyst: spherical shape have thick cell wall but difficult to diagnostic nuclei. 4