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Parasitology صادق الشيخ.د Helminthology Introduction Helminthology: The science which deals with the study of helminthes. Helminthes: The term used for all groups of worms that live as parasites. The Classification of Organisms : It is a procedure of putting organism's in-groups according to their food need. Basis of classification according to structural similarities called Taxonomy, 1- General appearance. 2- Arrangement of body parts. 3 – Type of feeding .4 –DNA and PCR . The five kingdoms are: 1- Manerous: are simple, single cell, some can make their own food others cannot. Ex: Bacteria. 2- Protist : are complex single cell, some can make their own food others cannot . Ex: in a drop of pond water Paramecium, Amoebae, Euglena. Phylum protozoa. 3- Fungi: are many –celled organisms that absorb food from dead and livings things, Ex: Mushrooms. 4- Plants: are many- celled organisms that make their own food, Ex: Roses, trees.... etc. 5- Animals: are many – celled organisms that cannot make their own food. Ex: Mice, birds, worm, man. Taxonomy: the science which deals with classification of animals, plants ... etc. ( Livings ) The six subdivisions of the kingdoms : Include :- Phylum Class Order 1 Family Genus Species Animal kingdom Vertebrates (40.000) spp one phylum with skeleton inside Their bodies invertebrates 3millions animals without back bone 8 phyla Classes:1 Mammalian 2 Birds 1 Sponge e.g. sponge 2 Coelenterate e.g. hydra 3 Platyhelminthes e.g. Tapeworms ,Flukes 4 Round worm e.g. Ascaris 5 Annelids e.g. leech and earthworm 6 Molluscus e.g. snails 7 Echinoderms e.g. Sea star 8 Arthropods e.g. Grass hopper, insects e.g. flies ,fleas ,bugs ,lice 6000spp 8000 spp 3 Amphibian Frog 2000 spp 4 Reptile korekodile 2000 spp 5 Fish carp 220000 spp 2 General characters of helminthes : 1:- They are multicellular bilaterally symmetrical animal. 2:-Very few worms' infections are potentially dangerous and the ability of these to produce clinical diseases is more often associated with: - No. of the parasites. - Unusual site in which they occur. - Re – infection. - Immunity of the host. 3- Unlike protozoa, most helminthes are unable to multiply within the host, so most helminthes infections are light. 4- Many helminthes have a limited distribution because they require a particular climate and the presence of reservoir or a suitable vector. 5- Many helminthes require another host to complete their life cycle. 6- The worms obtain their nourishment from hosts tissues or intestinal contents through their digestive system, but tape worms have no digestive system so they obtain their nourishment by absorption of predigest nutrients through their body wall. 7- The worms have parasite protective mechanisms which prevent the host damaging outer surface. 3 Methods of transmission 1- Fecal – oral route: infective eggs or larvae may swallowed by contaminated food or water e.g. Ascaris and Enterobius. 2- Swallowing of an infective larvae in the tissue of another host e.g. Tania solium, Tania saginata and Trichinella spiralis. 3- Active penetration of the skin by the larva e.g. Hook worms and Shestosoma sp. 4- Bite of blood sucking insects e.g. filarial worms 5- Inhalation of the infective eggs with air-dust, eggs too light to be spray with air-dust. E.g. Enterobius vermicularis. 6- Contact with contaminated people clothing sticky eggs adheres on the underwear of infected host e.g. E. vermicularis. Cestodes or Tapeworms General characters - The adult is usually found in the intestine of vertebrate and the larva develops in the tissues of various intermediate hosts. - The adult body is composed of scolex (head) ,neck and ribbon – like chain of segments (strobili) { immature ,mature and gravid segments} - All the tapeworms of man are hermaphroditic. - There is no mouth and no trace of an alimentary system, so nutrients are absorbed directly from host gut through the body wall. - Three groups of tapeworms infect humans:a- Tania group {Giant adult tapeworms} and Echinococcus {minute tapeworms}. b- Hymenolepis group and Dipylidium caninum. c- Broad fish tapeworm Diphyllobothrium latum. - All cestodes have indirect life cycle except Hymenolepis nana. 4 Pathogenesis Injuries produced by the worms are due to:Movements and migration Irritation Size and numbers Obstruction Pressure Atrophy Attachment Catarrhal inflammation Sharing host's nutrients Loss of weight Sucking blood Macrocytic anemia Adults Mechanical Action Larvae Adults Hemolysis Chemical action Tissue lysine Anticoagulins Larvae Inflammation Local necrosis Repairing Encapsulation Reaction Direct absorption of toxins General allergic responses Indirect nervous reflexes 5 Cestodes larvae (Metacestode): 1- Solid metacestodes : subdivided into :a- Procercoid sac-like solid structure with caudal appendage at its posterior end which contain hooks. b- Plerocercoid: chalky white solid structure composed of caudal solid appendage and invaginted head in the neck. 2- Bladder metacestodes : subdivided into – a- Cysticercoid: has a bladder filled with parenchyma e.g. Hymenolepis spp .and D.caninum. 6 b- Cysticercus : has fluid filled bladder with invaginated scolex .e.g.Taenia sp c- Hydatidcyst :metacestode of Echinococcus composed of bladder filled with fluid and surrounded by germinal and laminated layers . from germinal layer brood capsules arise which contain number of scolices . d- Coenurus : with multiple scolices , inside non laminated bladder ,arise from germinal layer e.g. Tania multiceps ------------------------------------------------------------------------------------------------ 7