Lec 10: Parasitology Classification of Human Parasite PDF

Lec 10: Parasitology Classification of human parasite By Dr. Shahad Mansour “A parasite is a smaller organism that lives on the expense of a larger organism called the host. A louse is a parasite and so is a virus.  Degree of injury Commensalism: an as...

Lec 10: Parasitology Classification of human parasite By Dr. Shahad Mansour “A parasite is a smaller organism that lives on the expense of a larger organism called the host. A louse is a parasite and so is a virus.  Degree of injury Commensalism: an association between two organisms in which one benefits and the other derives neither benefit nor harm. Mutualism: symbiosis that is beneficial to both organisms involved. Parasitism: the parasite benefit on the expanse of the host. A binomial system of nomenclature is used in which the scienti c name consists of the genus and species and written under lined. Classi cation systems have been developed to indicate the relationship among the various species of parasites, based on life cycles and morphology of the organism. Closely related species are placed in the same genus, related genera in the same family, related families in the same order, related orders in the same class, and related classes in the same phylum, which is one of the major categories in the animal kingdom. Kingdom phylum class order family Genus species fi fi Example 1 - Tiger Kingdom: Animalia (Animal) Phylum: Chordata (Vertebrate) Class: Mammalia (Mammal) Order: Carnivora (Carnivore) Family: Felidae (Cat) Genus: Panthera Species: Panthera tigris (Tiger)  parasites major divisions Parasites of humans are classi ed in six major divisions, These include: Protozoa —amebae (Entamoeba histolytica), agellates (Giardia lamblia), ciliates (Balantidium coli ), sporozoans (Plasmodium falciparum), coccidia (Toxoplasma gondii), microsporidia. Nematoda or roundworms (Ascaris lumbricoides). Platyhelminthes or atworms (cestodes: Taenia solium & Taenia saginata , trematodes (Fasciola hepatica). Pentastomids or tongue worms. Acanthocephala or thorny-headed worms. Arthropoda (e.g., insects like lice, scorpion, spiders, mites, ticks). fl fi fl Protozoa : Entamoeba histolytica and Entamoeba coli Entamoeba species, which possess a life cycle that alternates between the trophozoite stage and the cystic stage, can be either parasitic or non-parasitic. Entamoeba histolytica is the parasitic form which causes the food borne disease Amoebiosis which can be lethal upon the protozoan entering the circulatory system Entamoeba coli is the non-parasitic form and excreted via stools and can live as commensals in the large intestine. Entamoeba histolytica is transmitted via ingestion of the cystic form (infective stage) of the protozoa. cysts can be found in fecally contaminated soil or water. Excystation then occurs in the terminal ileum or colon, resulting in trophozoites (invasive form). The trophozoites can penetrate and invade the colonic mucosal barrier, leading to tissue destruction, secretory bloody diarrhea, and colitis. In addition, the trophozoites can spread through the blood via the portal circulation to the liver or other organs  Entamoeba histolytica Entamoeba coli observed in the feces in two observed in the feces in two Morphology stages, trophozoite and cyst stages, trophozoite and cyst Infective stage Cyst Cyst is a pathogenic parasite of is the non pathogenic Pathogenicity the large intestine and protozoa of the large causes amebic dysentery in intestine of human. humans. Microscopic stool Microscopic stool Diagnosis examination for examination for trophozoite and cyst trophozoite and cyst treatment Metronidazole Unnecessary Entamoeba histolytica: Two trophozoites have ingested erythrocytes, and all 3 trophozoites have nuclei Entamoeba histolytica Entamoeba coli