Introduction to Medical Protozoa Department of parasitology Shenyi He

General Concepts Eukaryotic OrganismsEukaryotic Organisms Generally unicellularGenerally unicellular Found in every conceivable damp habitatFound in every conceivable damp habitat Approximately 60,000 living speciesApproximately 60,000 living species Largest visible to the naked eyeLargest visible to the naked eye Smallest only seen with the EMSmallest only seen with the EM have all necessary life activities.have all necessary life activities.

Protozoa are one-celled animals found worldwide in most habitats. Most species are free living, but all higher animals are infected with one or more species of protozoa. Infections range from asymptomatic to life threatening, depending on the species and strain of the parasite and the resistance of the host. Protozoa are one-celled animals found worldwide in most habitats. Most species are free living, but all higher animals are infected with one or more species of protozoa. Infections range from asymptomatic to life threatening, depending on the species and strain of the parasite and the resistance of the host.

Structure Protozoa are microscopic unicellular eukaryotes that have a relatively complex internal structure and carry out complex metabolic activities. Some protozoa have structures for propulsion or other types of movement. Protozoa are microscopic unicellular eukaryotes that have a relatively complex internal structure and carry out complex metabolic activities. Some protozoa have structures for propulsion or other types of movement.

Classification On the basis of light and electron microscopic morphology, the protozoa are currently classified into seven phyla. Most species causing human disease are members of the phyla Sacromastigophora and Apicomplexa.

Classification Phylum Phylum :Class Genera Genera : SarcomastigophoraZoomastigophora Trypanosoma, Leishmania, Giardia, Trichomonas Lobosea Entamoeba, Naegleria, Acanthamoeba ApicomplexaSporozoea Plasmodium,Toxoplasma, Cryptosporidium, Isospora CiliophoraKinetofragminophoreaBalantidium

Reproduction Binary fission, the most common form of reproduction, is asexual; multiple asexual division occurs in some forms. Both sexual and asexual reproduction occur in the Apicomplexa. Binary fission, the most common form of reproduction, is asexual; multiple asexual division occurs in some forms. Both sexual and asexual reproduction occur in the Apicomplexa.

Nutrition All parasitic protozoa require preformed organic substances that is, nutrition is holozoic as in higher animals.

Life Cycle Stages The stages of parasitic protozoa that actively feed and multiply are frequently called trophozoites; in some protozoa, other terms are used for these stages. Cysts are stages with a protective membrane or thickened wall. Protozoan cysts that must survive outside the host usually have more resistant walls than cysts that form in tissues.The stages of parasitic protozoa that actively feed and multiply are frequently called trophozoites; in some protozoa, other terms are used for these stages. Cysts are stages with a protective membrane or thickened wall. Protozoan cysts that must survive outside the host usually have more resistant walls than cysts that form in tissues.

Basic structure 1. Cell membrane1. Cell membrane 2. Cytoplasm2. Cytoplasm organelles: pseudopodium(-dia- organelles: pseudopodium(-dia- amoeba); flagellum(-lla-flagellate); amoeba); flagellum(-lla-flagellate); cilium(cilia-ciliate) cilium(cilia-ciliate) 3. Nucleus: two kinds of nuclei:3. Nucleus: two kinds of nuclei: vesicular; vesicular; compact compact

Characteristics of Pathogenesis Characteristics of Pathogenesis 1. proliferation1. proliferation 2. Diffusion (disperse )2. Diffusion (disperse ) 3. Opportunistic parasitosis3. Opportunistic parasitosis

Ecological Niches in the Human Body: 1. Skin: Leishmania1. Skin: Leishmania 2. Eye: Acanthamoeba2. Eye: Acanthamoeba 3. Mouth: Amoebae and flagellates3. Mouth: Amoebae and flagellates (usually non-pathogenic) (usually non-pathogenic) 4.Gut: Giardia, Entamoeba (and invasion to4.Gut: Giardia, Entamoeba (and invasion to liver), Cryptosporidium, liver), Cryptosporidium, Isospora, Balantidium Isospora, Balantidium 5. G.U. tract: Trichomonas5. G.U. tract: Trichomonas

Ecological Niches in the Human Body: 6. Bloodstream: Plasmodium,6. Bloodstream: Plasmodium, Trypanosoma Trypanosoma 7. Spleen: Leishmania7. Spleen: Leishmania 8. Liver: Leishmania, Entamoeba8. Liver: Leishmania, Entamoeba 9. Muscle: Trypanosoma cruzi9. Muscle: Trypanosoma cruzi 10. CNS: Trypanosoma, Naegleria,10. CNS: Trypanosoma, Naegleria, Toxoplasma, Plasmodium Toxoplasma, Plasmodium