Introduction to Medical Parasitology (Second Part) PDF

Introduction to Medical Parasitology Second Part by Dr. Shaimaa Helmy Lecturer of Medical Parasitology parasitology Department Faculty of Medicine Helwan University  Objectives By the end of this le...

Introduction to Medical Parasitology Second Part by Dr. Shaimaa Helmy Lecturer of Medical Parasitology parasitology Department Faculty of Medicine Helwan University  Objectives By the end of this lecture, you will be able to recognize:  Factors affecting parasitic infections.  Different sources of infection.  Portal of entry to the host.  Important Definitions and terminology  General life cycle  PARASITIC DISEASE Competition between the parasite and the host for essential nourishments, e.g. vitamin  Mechanical injury  Allergic reaction  Immune reaction  Factors affecting the severity of the parasitic disease (1) Parasitic factors:  Virulence of the infecting strain of the parasite  Intensity of infection Factors affecting the parasitic disease (cont.) (2) Host factors:  Immune status of the infected person  Age  Occupation  Genetic  Economic conditions  Health education  Environmental conditions  Host Defense Against Parasite Natural host defense against parasite: Intact skin, salivary enzymes, tears and sweat stomach acidity. Genetic makeup of the host (some hosts are resistant to specific parasites). Maternal immunity. Wandering phagocytic cells. Acquired host defense against parasite: Humoral antibodies production Cytotoxic cells. Complement formation. Immune mediators e.g. Cytokines, Interleukins  Parasite Immune Evasion Intracellular location of the parasite. Intraluminal location of the parasite. Continuous changes of the outer surface of the parasite and antigenic variations. Location inside cyst forms (protective shell). Exhaustion of the immune system of the host through stimulation of producing of huge amount of non-specific antibodies.  Sources of infection  Contaminated soil and water  Fresh water fishes and crabs  Raw or undercooked meat  Plants or vegetables  Arthropods e.g. blood sucking insects, house fly  Domestic or wild animals  Man  Portal of entry into the body  Mouth or oral: faecal-oral route  Skin e.g. direct penetration , blood sucking arthropods  Sexual transmission  Congenital (transplacental)  Inhalation  Blood transfusion Mechanisms by which the parasite causing a disease (Pathogenicity) 1- Traumatic damage * At the site of entry e.g. skin * During migration e.g. lung * During escape * Attachment to the intestinal wall 2- Mechanical blockage * Intestine * Lymph flow 3- lytic necrosis * Enzymes for nutritional needs and penetration into tissues 4- Competition with the host for specific nutrients * Vitamins, minerals. 5- Inflammatory reaction * Cellular proliferation & fibrous encapsulation * Eosinophilia 6- Allergic manifestations * Secretion and excretion from parasite 7- Neoplasia 8- Secondary infection * Migration of larvae from intestine may carry bacteria and viruses to the blood  Definitions Life cycle The evolution of the parasite through sequence of different morphologic stages, environments and hosts (To allow the parasite to survive and reproduce).  Types of Life cycles Direct or simple life cycle: one host Human human Indirect or complex life cycle: more than one host Human animal human Free living: in the environment Under certain conditions infective  Definitions (cont.) Infective stage The developmental stage that is capable to cause the parasitic infection in the final host. Mode of infection The method by which the infective stage enter the host  Definitions (cont.) Diagnostic stage The developmental stage that could be detected to denote an actual infection Diagnosis  Definitions (cont.) Habitat A place that the parasite reside inside the host.  Definitions (cont.) Prepatent period The time taken from the start of infection until appearance of the parasite inside or outside the host. Incubation period The time between the infection and appearance of the clinical manifestations.  Life cycle Definitive host Reservoir host Inside the host Habitat Diagnostic stage Infective stage Adult stage Immature stage Outside the host Intermediate host  Host-Parasite interaction diagnosis treatment Parasitic pathogenesis PARASITE disease Prevention &control Infective Human Diagnostic stage stage External environment Intermediate host  Nomenclature of parasite Schistosoma mansoni Genus species  ‫‪Points to be studied in any Parasite‬‬ ‫‪Geographical Distribution‬‬ ‫هل هناك اصابات بهذا الطفيل فى بلدنا أم ال؟‬ ‫)‪Definitive host (Final host‬‬ ‫العائل الذى يئوى الطفيل البالغ‬ ‫) ‪Habitat ( adult parasite‬‬ ‫المكان (فى جسم المريض) حيث يستقر الطفيل البالغ‬ ‫‪Intermediate host‬‬ ‫العائل الذى يأوى األطوار الغيرناضجة‬ ‫‪Mode of Infection & infective stage‬‬ ‫طريقة العدوى والطور المعدى‬ ‫‪Pathogenesis‬‬ ‫كيف يحدث الطفيل أضرارا فى جسم المريض‬ ‫‪Clinical picture‬‬ ‫شكوى المريض والعالمات التى يجدها الطبيب عند الكشف على المريض‬ ‫‪Methods of diagnosis & Diagnostic‬‬ ‫وسائل التشخيص والطورالتشخيصى‬ ‫‪stage‬‬ ‫‪Treatment‬‬ ‫الخطوط العريضة للعالج‬ ‫‪Prevention and Control‬‬ ‫كيفية الوقاية من االصابة بهذا الطفيل‬ ‫‪19‬‬