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Medical Biology Lab. 11.pdf

  1. Blood and tissue flagellates
  2. Blood and tissue flagellates  +Known as the Hemoflagellates, live in blood ,tissue and lymph of their vertebrate hosts .  +They are transmitted by blood-sucking insects and undergo a developmental cycle  the arthropod serves as intermediate host  +flagellates may be occur in four different morphological forms: amastigote, promastigote, epimastigote and trypomastigote  +They move by a single flagellum arise from kinetoplast  + they multiply by binary fission
  3. Leishmania  Leishmania species are unicellular eukaryotes having a well-defined nucleus and other cell organelles including kinetoplast and flagella.  Depending on the stage of their lifecycle, they exist in two structural variants, as:  The amastigote form is found in the phagocytes cells and circulatory systems of humans.  It is an intracellular and non-motile form, being devoid of external flagella.  It is oval in shape, and measures 3–6 µm in length and 1–3 µm in width.  One large centric nucleus presence .  The kinetoplast and basal body lie towards the anterior end.
  4.  The promastigote form is found in the alimentary tract of sandflies.  It is an extracellular and motile form.  It is larger and highly elongated, measuring 15-30 µm in length and 5 µm in width.  It is spindle-shaped, tapering at both ends.  A long flagellum (about the body length) is projected externally at the anterior
  5.  Leishmania tropica are a protozoan endoparasite, residing in human skin causing cutaneous leishmaniasis or oriental sore (Baghdad boil).  The primary host is man whereas the secondary host are sand-flies of the genus Phlebotomus.  L. tropica is endemic in the Mediterrean, Black sea countries, It is common in Syria, Arabia, Iraq, Iran.  Leishmania donovani is a protozoan endoparasite inhabiting the cells of reticulo-endothelial system ( liver, spleen, bone marrow ,lymph nodes) of human beings causing visceral leishmaniasis (kala-azar ,Dum Dum fever, black fever).  The primary host is man, whereas the secondary host is sand-fly.  It is common in Asia,North and East Africa and America.
  6. Trypanosoma  Trypanosoma is a genus of unicellular flagellates. Most trypanosomes are transmitted via a vector blood-feeding invertebrates (generally found in the intestine) but normally occupy the blood stream or an in the mammalian host.  Trypanosomes infect a variety of hosts and cause various diseases, including  the fatal human diseases sleeping sickness, caused by Trypanosoma brucei gambiense , Trypanosoma brucei rhodesiense  Chagas disease, caused by Trypanosoma cruzi. o The blood-sucking flies known as Tse-tse fly of the genus Glossina.  The African trypanosomes show two morphologic forms: epimastigote and trypomastigote.  It resides in the blood plasma of man. Often they are found in the cerebro-spinal fluid, spleen and lymph nodes.  The trypomastigote have elongated bodies 15-31µ with one nucleus near the center and one kinetoplast near the posterior end ,undulating membrane and a free flagellum are found.
  7.  T. cruzi has three morphological forms: the trypomastigote, the epimastigote, and the amastigote.  Trypanosomes are present in the circulating blood.  They are approximately 20 mm long and generally slender.  They have a thin, irregularly shaped of undulating membrane.  They have a centrally positioned nucleus, and a kinetoplast located towards the posterior.  A flagellum stems from the kinetoplast and runs through the remainder of the parasite and also extends beyond it.
  8.  sporozoans are obligate intracellular parasitic and pathogenic, reproduction cycle has both asexual and sexual phases.  The asexual phase is termed schizogony (from the Greek, meaning generation through division), The sexual phase is known as sporogony (generation of spores) and is followed by gametogony or the production of sexually reproductive cells termed gametes.  Sporozoans have no flagellated extensions for locomotion, with most species presenting only gliding motility.  Two genera Plasmodium (P. falciparum, P. malariae, P. vivax, P.ovale)and Toxoplasma gondii will be demonstrated. 3- Sporozoa
  9. Plasmodium  Plasmodium is a genus which cause malaria in their hosts  The parasite always has two hosts in its life cycle, the insect Mosquitoes of the genus Anopheles and vertebrates host.  The sexual stages occur in mosquitoes while the asexual stages occur in human liver and then in the blood.  Four species of plasmodium P. falciparum, P. malariae, P. vivax, P.ovale case malaria which is widespread in the tropics and subtropic regions.  Malaria is characterized by successive period of chills, followed by fever and sweating.  Transmission mainly occur through Anopheles bites. However , cases of transmission through blood transfusion and organ transplantation are also possible.  Diagnosis The preferred method to diagnose malaria and identify the species of Plasmodium is by microscopic examination of a blood film . The trophozoites of P.falciparum and P.vivax showed a ring stage in infected red blood cell
  10. Toxoplasma gondii  Toxoplasma gondii is a protozoan parasite that infects most species of warm blooded animals, including humans, and can cause the disease toxoplasmosis.  The lifecycle of T. gondii can be summarized into two stages:  a sexual stage that occurs only within cats in the intestinal epithelia (the definitive host)  an asexual stage that can occur within all warm-blooded animals, including humans, cats, and birds(intermediate host).  In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host.
  11.  Tachyzoite replaces the previously used term trophozoite, is often crescent shaped, approximately 2 by 6 μm with a pointed anterior end and a rounded posterior end, the nucleus is spherical and is more centrally located.  Tachyzoites multiply asexually within the host cell, responsible for the acute infection. Such parasite are enclosed inside the cell to form bradyzoite (pseudocyst) in host with well immunity level.  Bradyzoite slowly divide within a tissue cyst.  Cysts are mainly found in neurological tissue and muscle tissues.  Bradyzoites is crescent-shaped, 7 by 1.5 μm in size , responsible for the chronic toxoplasmosis, nucleus situated toward the posterior end  Humans can be infected by ingesting undercooked meat containing tissue cysts with bradyzoites or from food/water contaminated by oocysts. Humans can also be infected through blood transfusion or organ transplantation. In addition, infection can be transmitted from mother to fetus
  12. tachyzoites Bradyzoites within cyst
  13. 4- Ciliata The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia for locomotion. One species ( Balantidium coli) is known to infect human. Balantidium coli  Balantidium coli is a pathogenic protozoan cause balantidiasis ,live in the large intestines,has two developmental stages a trophozoite stage and a cyst stage.  Trophozoites  measure between 50-130 m long by 20-70 m wide.  clear ectoplasm encloses a granular and dense endoplasm . trophozoite
  14.  Two nuclei are visible, the macronucleus is long and sausage-shaped and the spherical micronucleus.  The opening, known as the peristome, at the pointed anterior end leads to the cytostome, or the mouth. Numerous food vacuoles and two contractile vacuoles are seen.  Cyst  are spherical and smaller than trophozoite measuring 40-60 µm, round and have only the macronucleus and contractile vacuoles.  Balantidium coli reproduces either by asexual binary fission or sexual conjugation.  parasites can be transmitted through the fecal-oral route by contaminated food and water with the infective stage (cyst). cyst