Protozoa PDF

Life cycle During a blood meal on the mammalian host, an infected tsetse fly (genus Glossina) injects metacyclic trypomastigotes into skin tissue. The parasites enter the lymphatic system and pass into the bloodstream. Inside the host, they transform into bloodstream trypomastigotes , a...

Life cycle During a blood meal on the mammalian host, an infected tsetse fly (genus Glossina) injects metacyclic trypomastigotes into skin tissue. The parasites enter the lymphatic system and pass into the bloodstream. Inside the host, they transform into bloodstream trypomastigotes , are carried to other sites throughout the body, reach other blood fluids (e.g., lymph, spinal fluid), and continue the replication by binary fission. The entire life cycle of African Trypanosomes is represented by extracellular stages. The tsetse fly becomes infected with bloodstream trypomastigotes when taking a blood meal on an infected mammalian host ( , ). In the fly’s midgut, the parasites transform into procyclic trypomastigotes, multiply by binary fission , leave the midgut, and transform into epimastigotes. The epimastigotes reach the fly’s salivary glands and continue multiplication by binary fission. The cycle in the fly takes approximately 3 weeks. Humans are the main reservoir for Trypanosoma brucei gambiense, but this species can also be found in animals. Wild game animals are the main reservoir of T. b. rhodesiense.  C- Subphylum: Sarcodina (Amoebozoa) They are protozoans whose body is surrounded by a thin protoplasmic membrane with no definite shape. The pseudopodia are the organs of locomotion, and they also help in feeding. They live as: 1. Free-living e.g. Amoeba 2. Commensal e.g. Entamoeba coli 3. Parasitic e.g. Entamoeba histolytica.  Class: Lobosea Ex. Amoeba proteus Amoeba usually lives in well- oxygenated fresh-water, typically on decaying vegetation from pools, ponds and streams. Regulation of water is carried out by the contractile vacuole through Osmosis. It moves and captures its food by means of temporary pseudopodia at any place of its cell body. This sort of irregular flowing is termed as amoeboid movement which is the result of changes within the colloidal protoplasm, from the fluid “sol’’ to the more solid “gel” condition. Feeding in Amoeba sp  Parasitic amoebae Class: Archamoeba There are six genera of parasitic amoebae: Five in the intestinal tract and one in the buccal cavity, from them: A. Intestinal commensal Ex. Entamoeba coli B. Intestinal parasitic amoebae Ex. Entamoeba histolytica C. Buccal commensal Ex. Entamoeba gingivalis  Comparison between Entamoeba histolytica and E. coli Entamoeba coli Entamoeba histolytica Lives in the lumen of large intestine as a Lives in the wall of large intestine as a Habitat commensal feeding on bacteria. dangerous endoparasite since it feeds on the tissues and blood of its host causing the disease “amoebic dysentery”. - The ectoplasm and endoplasm are not - The ectoplasm and endoplasm are Trophozoite clearly differentiated. well differentiated. (Feeding - With two pseudopodia. - With single large pseudopodium. stage) Morphological stages - Nucleus with lateral karyosome. - Nucleus with central karyosome. - Chromatin granules are irregularly - Chromatin granules are regularly distributed on the inner nuclear distributed on the inner nuclear membrane. membrane. - Food vacuoles contain bacteria. - Food vacuoles contain RBCs. - Round or ovoid Precyst - Lack a cystic wall - Vacuoles containing glycogen and rod-like chromatoid bodies. Mature cyst with 8 nuclei. Mature cyst with 4 nuclei. Cyst (Infective stage)  Entamoeba histolytica Entamoeba coli Trophozoite Trophozoite Cyst Cyst Life cycle of E. histolytica  (II)- Phylum Apicomplexa Class Sporozoa Levine (1970) They are protozoan parasites which live as internal parasites (endoparasites) in higher animals. It contains organisms that possessed the apical complex which include polar ring, micronemes, rhoptries, subpellicular microtubules, micropore(s) and conoid which help in penetrating host.  Subclass Coccidia Plasmodium sp. They are intracellular blood parasites of blood cells and tissues of birds and mammals. They causes to human several diseases, which transmitted by blood sucking arthropods acts as intermediate hosts. There are four species of Plasmodium causing malaria to man: 1. Plasmodium vivax 2. P. malariae 3. P. ovale. Erythrocytes 4. P. falciparum Leucocyte  Life cycle of Plasmodium sp. 1- Exerythrocytic cycle (Liver stage) 2- Erythrocytic cycle (Human blood stage) 3- Mosquito stage  Life cycle of Plasmodium sp. Female Anopheles mosquito (Final Man (Intermediate host) host) 1. Schizogony in liver cells (Exo- 1. Gamogony (Sexual cycle erythrocytic cycle) inside the stomach of A. Primary tissue phase mosquitoes). B. Secondary tissue phase or 2. Sporogony (Asexual cycle in Re-infection haemolymph of mosquitoes) 2. Schizogony in RBCs (Erythrocytic cycle)