Introduction of Medical Parasitology PDF

Introduction of Medical Parasitology By Dr. Mona Mohammed Saleh lecturer of parasitology Faculty of medicine Menoufia university  Introduction  Medical Parasitology: it is the science that deals with the study of the organis...

Introduction of Medical Parasitology By Dr. Mona Mohammed Saleh lecturer of parasitology Faculty of medicine Menoufia university  Introduction  Medical Parasitology: it is the science that deals with the study of the organisms (parasites) that infect and produce diseases in human.  Parasite: is a living organism, which lives in or upon another organism (host) and derives nutrients directly from it, without giving any benefit to the host.  Host: it is a living organism that harbors the parasite  Types of hosts:  Definitive host: it is the host that harbors the mature stage of the parasite.  Intermediate host: it is the host that harbors the immature stage of the parasite.  Reservoir host: it is an animal that harbors the mature stage of the parasite.  Vector: an arthropod which carries the parasite from one host to another host. Medical parasitology is calssified into:  Helminthology: a) Class:Trematoda b) Class:Cestoda c) Class:Nematoda  Protozology  Arthropodology  Parasites may be classified as:  Ectoparasite: They inhabit the surface of the body of the host without penetrating into the tissues. The infection by these parasites is called infestation, e.g., fleas or ticks.  Endoparasite: They live within the body of the host (e.g., Leishmania). Invasion by the endoparasite is called infection.  Temporary parasite: visits the host to take its blood meal (mosquitoes).  Permanent parasite: lives in or on the host the whole of its life (Ascaris lumbricoides)  Facultative parasite: lives as parasite or free living (Strongyloides stercoralis).  Obligatory parasite: can"t live without it"s host )lice).  Specific parasite: affects one specific particular host (Entrobius vermicularis).  Nonspecific parasite: normally it inhabits and completes its life cycle in an animal host but can inhabits a human host without completing its life cycle (Avian schistosomes and Toxocara canis).  Opportunistic parasite: it can cause disease only in immunodeficient individuals, while no symptoms appear in immunocompetent individuals (e.g. Cryptosporidium).  Sources of Infection:  Man: Blood and human excreta (stool, urine, sputum) containing the infective stage of the parasite (e.g., toxoplasmosis, amoebiasis, enterobiasis, etc.).  Animal:  Raw or under cooked meat containing the infective stage of the parasite e.g Taenia saginata & Taenia solium.  Animal Stool containing different stages of the parasite.  The infection which is transmitted from infected animals to humans is called zoonosis.  Contaminated soil: Soil polluted with human or animal excreta containing eggs of the parasites can act as an important source of infection, e.g., Hookworm, Ascaris species, Strongyloides species and Trichuris species.  Contaminated water: with the infective stage of the parasite. e.g. E. histolytica or Giardia lamblia, can act as source of infection. Modes of Transmission  Ingestion: Infection is transmitted orally by ingestion of food, water or vegetables contaminated with feces containing the infective stages of the parasite. (e.g., cysts of E. histolytica, and ova of Ascaris lumbricoides)  Penetration of the skin and mucous membranes: Infection is transmitted by penetration of the skin by the larval forms of the parasite (e.g., filariform larva of Strongyloides stercoralis and hookworm)  Sexual contact: Trichomonas vaginalis is the most frequent parasite to be transmitted by sexual contact.  Vertical transmission: Mother to fetus transmission is important for some parasitic infections like Toxoplasma gondii, Plasmodium spp. and Trypanosoma cruzi.  Blood transfusion: Certain parasites like Plasmodium species, Babesia species, Toxoplasma species, Leishmania species and Trypanosoma species can be transmitted through transfusion of blood or blood products.  Autoinfection: some intestinal parasites may be transmitted to the same person by contaminated hand (external autoinfection) or by reverse peristalsis (internal autoinfection). e.g. Cryptosporidium parvum, Taenia solium, Enterobius vermicularis, Strongyloides stercoralis and Hymenolepis nana.  Inhalation: of dust carrying the infective stage of the parasite, e.g (Entrobius vermicularis.  Contact with infected patient e.g scabies.  Bite of vectors: Many parasitic diseases are transmitted by insect bite such as: malaria (female anopheles mosquito), filariasis (Culex), leishmaniasis (sandfly), Chagas’ disease (reduvid bug) and African sleeping sickness (tsetse fly) Diagnosis of parasitic diseases Several ways are important in establishing the specific diagnosis of various parasitic infections.  1-Clinical diagnosis: case history, symptoms and signs. Successful diagnosis depends upon:  II- Laboratory diagnosis: Direct: demonstrating the diagnostic stage of the parasite in the collected sample (stool, urine, sputum, blood). Parasitic diagnosis can be done either microscopically or macroscopically and detecting the different stages of the parasite by culture. Indirect: finding indicator for the presence of parasitic infection.  Intradermal skin tests  - Immunodiagnostic methods (antigen and antibody detection)  Molecular methods: DNA probes and polymerase chain reaction (PCR)  III-Imaging techniques: X-ray and ultrasonography  IV-Biopsy Medical parasitology is calssified into:  Helminthology: a) Class:Trematoda b) Class:Cestoda c) Class:Nematoda  Protozology  Arthropodology