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What is parasite and it's types

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  1. 1. 1
  2. 2. By: S h a r a f a t A l i BSZool F13E-23 Parasite and it's Classifications 2
  3. 3. Learning Objectives 1. What is parasites. 2. What is helminthes and classes of helminthes. 3. What is platyhelminthes: – General morphological characters. – General outline of the life cycle. – On the basis of dependency. 3
  4. 4. Parasite A parasite is an organism that lives on or in a host and gets its food from or at the expense of its host. There are three main classes of parasites that can cause disease in humans: Protozoa Helminths Ectoparasites 4
  5. 5. Helminths Helminths are large, multicellular organisms that are generally visible to the naked eye in their adult stages. Platyhelminthes (Flatworms) Nematodes (Roundworms) Acanthocephala (Thorny-headed worms) 5
  6. 6. Platyhelminthes(Flatworms) Flatworms are unsegmented, bilaterally symmetrical worms that lack a coelom (acoelomate) but that do have three germ layers. Flatworms have a cephalized nervous system that consists of head ganglion. Excretion and osmoregulation of flatworms is controlled by "flame cells" located in protonephridia 6
  7. 7. Conti… Class Turbellaria (turbellarians, flatworms) Class Monogenea (parasitic flukes) Class Trematoda (parasitic flukes) Class Cestoda (tapeworms) 7
  8. 8. Nematodes(Roundworms) General morphological characters Bilateral symmetrical Has body cavity Separate sexes Elongate and Cylindrical Intestinal (Small and large intestine and non- intestinal (tissue nematodes) 8
  9. 9. Life Cycle Adult → egg → larva → adult. Tissue nematodes are viviparous (lay larvae). Larva molts its cuticle 3 times. 9
  10. 10. Cestodes (Tapeworms) General morphological characters.  Hermaphrodite.  Ribbon-like flattened and bilaterally symmetrical.  There is neither body cavity nor digestive tract.  The body is formed of 3 parts:  Head (Scolex) which is provided by organs of attachment.  Neck is composed of actively dividing cells (stem cells) and it is responsible for giving rise to new segments.  Body is composed of several segments (Immature, Mature and Gravid segments). 10
  11. 11. Life Cycle Adult → egg → cysticercus (the larval stage) → adult, Except for D. latum, give oval operculated egg containing hexacanthembryo (coracidium). All cestodes require one intermediate host (usually vertebrate), except D. latum requires two intermediate hosts. H. nana does not require an intermediate host. 11
  12. 12. Trematodes(Flukes) 12 General morphological characters: •Hermaphrodite except blood flukes (Unisexual) •Leaf-like, flattened and bilaterally symmetrical •There is no body cavity.
  13. 13. Life Cycle Adult → egg → miracidium → sporocyst→ redia→ cercaria → metacercaria→ adult. Egg is operculated, and should reach to a water source to hatch. The first intermediate host is snail, and the second (if present) is marine creature. Except for Schistosoma, egg has a spine, no redia and no metacercaria. 13
  14. 14. On the basis of Dependency 1) Obligate parasites- These parasites can only survive in a host and therefore go directly from one host to another. This may involve complex life cycles e.g. Trichomonas Taenia Trichinella 14
  15. 15. Conti… 2) Temporary parasites- These parasites spend only part of their lives as a parasite and another part as free-living organism. e.g. Fasciola hepatica (Liver fluke) Schistosoma Ascaris Haemonchus 15
  16. 16. Conti… 3) Facultative Parasite- These parasites which can live in host if it is available, but capable of living independently if it’s host is not available, are known as facultative parasite. e.g. Naegleria Acanthamoeba Fungi such as Candida (vaginal candidosis, athlete foot) 16
  17. 17. Refernces:  Hickman, C.P. and L. S. Roberts. 1994. Animal Diversity. Wm. C. Brown, Dubuque, IA.  Brusca, R. C., and G. J. Brusca. Invertebrates. 1990. Sinauer Associates, Sunderland, MA.  Ash L, Orihel TC: Parasites: A Guide to Laboratory Procedures and Identification. American Society of Clinical Pathologists, Chicago, 1987 .  Bogitsh BJ and Cheng TC: Human Parasitology. WB Saunders, Philadelphia, 1990 .  Castro GA: Trematodes: schistosomiasis. p 1710. In Kelly WN (ed): Textbook of Internal Medicine. JB Lippincott, Philadelphia, 1989 .  Hunter GW, Swartzwelder JC, Clyde DF: A Manual of Tropical Medicine. 5th Ed. WB Saunders, Philadelphia, 1976 .  Jeffrey HC, Leach RM: Atlas of Medical Helminthology and Protozoology. Churchill Livingstone, Edinburgh, 1968 .  Lee DL: The Physiology of Nematodes. Oliver and Boyd, Edinburgh, 1965 .  Smyth JD: The Physiology of Trematodes. Oliver and Boyd, Edinburgh, 1966 .  Schmidt GD, Roberts LS: Foundations of Parasitology. 3rd Ed. Times Mirror/Mosby College Publishers, St Louis, 1985 .  Zamen V: Atlas of Medical Parasitology. Lea&Febiger, Philadelphia, 1979 . 17