Parasitic Classification, Structure and Replication PDF

Parasitic Classification, Structure And Replication Dr. Lorina Badger-Emeka COM – KFU  Intending Learning outcomes Students should be able to: Describe the kingdom Parasitic Animalia of Medical Importance Know the characteristics of the major...

Parasitic Classification, Structure And Replication Dr. Lorina Badger-Emeka COM – KFU  Intending Learning outcomes Students should be able to: Describe the kingdom Parasitic Animalia of Medical Importance Know the characteristics of the major groups of Parasites Know how Protozoa are able to adapt to harsh environmental conditions  Introduction Parasitology can be defined as the scientific study of Parasites The study evaluates the relationship between parasitic organisms and their host When applied to humans, it evaluates the relationship between parasites that invade and cause damage to the human body  Introduction 2 Parasitism is an association between two organisms where one organism is harmed and the other lives at the expense of it The one harmed is the host And the one deriving benefits from the host is the parasite  Parasites of Human Medical Importance [Definitions] Parasites: An organism that lives on or in a host organism And cause harm to this host. Host: A living organism that harbors the parasite (Definitive, intermediate, reservoir). Vector is an arthropod (insect) transmitting infection from one host to another. Estimated worldwide disease burden of parasitic infections Classification of medical Parasitology  Classification of medical Parasitology Parasites of medical importance can be grouped in two kingdoms: Protista [microscopic single cell Animalia [multicellular, macroscopic, possessing eukaryotes such as protozoa] well differentiated tissue and organs] Giardia lamblia  Classification of medical Parasitology 2 Medical Protozoology: study of medically important protozoa Medical Helminthology: study of helminths (worms) that infect man. Medical Entomology: study of arthropod which cause or transmit disease to man Groups of Parasite Of Medical Importance intestinal and urogenital protozoa, blood and tissue protozoa, nematodes, trematodes, cestodes, and arthropods Main Characteristics of the major Groups of Parasites [Protozoa]  Protozoa Protozoa are single celled with size ranging between 2 - 100µm. They are divided into four types classified based on their organs of locomotion.  Protozoa 1: Rhizopoda [amoebas]. They move with the aid of Pseudopodia. E.g., of medical importance is Entamoeba histolytica which may invade tissue and cause disease Entameoba histolytica (amoebic dysentery)  Entamoeba histolytica trophozoite (A) And cyst (B). Trophozoites are motile and vary in size. The cysts are smaller and contain one to four nuclei (usually four). Image courtesy Murray et al. 7th Edition B The main characteristics of Protozoa 2- Flagellates  Giardia lamblia The morphology gives the appearance that the trophozoites are looking back at the viewer Giardia lamblia trophozoite (A) and cyst (B). Flagella are present, two nuclei with large central karyosomes, Cysts are smaller Image: Murray 7th Edition  Protozoa 2:Mastigophora [Flagellates] Trypanosomes, Leishmania, (capable of invading blood and tissue of humans where they cause disease). Trichomonas, Giardia [gastrointestinal and urogenital tracts] Trypanosoma cruzi (sleeping sickness) The main characteristics of Protozoa 3-Ciliates Ciliophora: Balantidium coli The main characteristics of Protozoa 4 Sporozoa  Plasmodium falciparum in erythrocytes (red blood cell) Sporozoa: no form of independent movement exhibited. or Amoeboid movement when present. E.g. Plasmodium and Toxoplasma spp. They are all parasites Producing two of the most lethal diseases of mankind. Malaria and Toxoplasmosis How do protozoa adapt to harsh (unfavorable) environmental conditions ? Under harsh or unfavorable environmental conditions, Some parasitic protozoa develop into a cyst form The cyst is less metabolically active. It is surrounded by a Thick external cell wall needed for protection Ciliophora: Balantidium coli (Cyst) The protozoan parasite possesses the ability of being transformed from an active (trophozoite) to an inactive stage. It loses its power of motility and encloses itself within a tough wall.  Protozoan Cyst The protoplasmic body formed as a result of this, is known as a cyst. The cyst is the resistant stage of the parasite It is also infective to the human host. The cyst is an integral part of the life cycle of protozoan parasites It facilitates the transmission of organisms from host to host in the external environment Surviving unfavorable condition those that do not form cysts rely on direct transmission or Through an arthropod vector for completion of life cycles How do protozoa adapt to harsh (unfavorable) environmental conditions ? 2 Also, other protozoan parasites have developed Immuno-evasive mechanisms This allows them respond to attack by the host immune system How? By continuously changing their surface antigens to escape from The immune system of the host Summary Metazoa (Animalia)  The Helminths (Worms) The helminthic parasites are multicellular, bilaterally symmetrical animals having three germ layers. Those that are of medical importance to human beings are divided into three main groups. Cestodes Trematodes and Nematodes  Helminthic Parasites of Humans Tapeworms Cestodes Tape like, segmented Has a head with suckers No separate sexes No body cavity No alimentary canal  They are leaf like Unsegmented; Can be monoecious [Not separate sexes] Trematodes or dioecious [such as the blood fluke. E.g.. Schistosomes] No suckers Body cavity sometimes present or absent  Nematodes Elongated, Cylindrical Separate sexes They have no suckers or hooks They have a body cavity They have an alimentary canal The main characteristics of Helminths [Summary]. Murray et al., 9th Ed. Medically important Arthropods Summary  Classification of Medically Important Parasites Protozoa Metazoa {Helminths} Sarcodina {Amoeba: E. histolytica} Platyhelminthes: Mastigophora {Flagellates: Trichomonas sp.} Trematodes {Schistosomes} Sporozoa Plasmodium, Toxoplasma} Cestoda {Tapeworms} Ciliates Nemathelminthes {Roundworms} CLASSIFICATION OF ARTHROPODS Kingdom Animalia Phylum Arthropoda Class Insecta Arachnida Crustaceans Pentastomida E.g. mosquito e.g. Ticks e.g. crabs  Concluding Questions The protozoa causing dysenteric symptoms is A. Balantidium coli B. Entamoeba coli C. Trichomonas species  Concluding Questions 2 Which of the following diseases are transmitted by arthropod vector: a. Malaria b. Schistosomiasis c. Hydatid cyst  Medical Microbiology. by Patrick R. Murray. 6th or 7th Edition Chapters 76, 77 References 8th edition, Chapter, 68