Introduction to Parasites PDF

Introduction to Parasites  Introduction Parasite is an organism baring food and shelter temporarily or permanent and living in or on another organism. The study of parasites is called Parasitology. Parasites can be 1. Facultative parasite: parasites able to live bot...

Introduction to Parasites  Introduction Parasite is an organism baring food and shelter temporarily or permanent and living in or on another organism. The study of parasites is called Parasitology. Parasites can be 1. Facultative parasite: parasites able to live both free living and parasite living e.g. Strongyloides species. 2. Obligate parasite: parasite living permanently in a host and cannot live without a host e.g. Trichomonos species. 3. Coprozic (spurious) parasites: foreign, pass through alimentally canal without affect. Clinical Parasitology: deals with animal parasites of man and their medical importance.  Parasitology Divisions of Parasitology: 1. Protozoa 2. Helminthes a. Roundworms (nematodes) b. Flatworms – Cestodes (tapeworm) Trematode (fluke) Parasitism: organism depend upon another for living, one is living at the expense of the other and harmful, called Parasite, the other organism is called Host.  Host: organism harboring the parasite species may be affected or not. Classification of Hosts: 1-Definitive host: harbors the adults or final stages or sexual stages (♂♀) in the development of parasite ex: man. 2-Intermediate host: in which you have the larva stages or Inter mediate stages in the development. Ex: Taenia adult------ man Larva –--- cattle 3-Reservoir host (carrier): the carrier host is well adapted to the parasite and tolerates the infection but serve as source of the infection to other organisms. Relationships between organisms: Symbiosis: permanent association between two organisms Mutualism: two organisms living together, the two organisms benefit. Commensalism: Two organisms Living together, one is benefited and the other is not been affected. When the other organism become affected, then the relationship turns = Parasitism. Zoonosis: disease of animals but can be transmitted to a man. Ex: Hymenolepis nana.  Classification of parasites General classification: animal parasites are classified according to international code taxonomy – Each parasite belong to a: Kingdom Phylum Class Order Family Genus Species Some have further divisions to: Sub – order, super family, sub – species in classification, scientific parasitic name is of 2 parts: Genus name and species name. Ex: Plasmodium Falciperum Genetic name (one word): plasmodium Species name (two words): plasmodium falciperum. Genus: means group of close related species. Species: means population with the same genetic characters.  Classification of parasites Parasites Protozoa Helminthes Blood and Intestinal Urogenital Cestodes Trematodes Nematodes tissue  Protozoa Intestinal Blood and tissue Urogenital tract Malaria Entamoeba histolytica Toxoplasma Giardia lamblia Trichononas Vaginalis Trypanosoma Cryptosporidium Leishmaina MEDICAL PROTOZOOLOGY Protozoa: These are unicellular organisms that occur singly or in colony formation. Each protozoan is a complete unit capable of performing all functions. Morphology: Protozoa have wide range of size (1-150μ). The structure of protozoan cell is formed of a cytoplasmic body and a nucleus. 1. Cytoplasm: a. Ectoplasm: The outer hyaline layer that is responsible for ingestion of food, excretion, respiration, protection and sensation. Some structures develop from ectoplasm as: - Organs of locomotion; pseudopodia, flagella and cilia. - Organs for food intake or excretion; peristome, cytostome and cytopyge. b. Endoplasm: The inner granular part of cytoplasm that is responsible for nutrition and reproduction. The endoplasm contains number of structures as: food vacuoles, foreign bodies, contractile vacuoles and chromatoid bodies. 2. Nucleus: It is the most important structure, as it regulates the various functions and reproduction. It is formed of Nucleus: It is the most important structure, as it regulates the various functions and reproduction. It is formed of: a. Nuclear membrane. b. Nuclear sap (nucleoplasm). c. Chromatin granules. d. Karyosome (nucleolus): It is a DNA containing body, situated centrally or peripherally within the nucleus Biology of protozoa: 1. Movement: Protozoa may move by pseudopodia, cilia and flagella with or without undulating membrane. 2. Respiration: It may be by direct taking of oxygen or by using oxygen liberated from metabolic processes. 4. Excretion: It is performed by osmotic pressure, contractile vacuoles, diffusion 5. Protozoan cell can secrete cyst wall, digestive enzymes, pigments, proteolytic enzymes, haemolysins, cytolysins, toxic and antigenic substances. 6. Reproduction: The parasite multiplies only in the trophozoite stage. The methods of reproduction are of the following types: I. Asexual reproduction: 1. Simple binary fission: It is either longitudinal or transverse into two organisms. 2. Multiple fission (schizogony, merogony or sporogony): In this process the nucleus undergoes several successive divisions followed by division of cytoplasm into small parts to produce large number of small merozoites or sporozoites within the schizont, e.g. Plasmodium. 3. Budding: Classification of Protozoa 1. Phylum: Sarcomastigophora (Amoebae and Flagellates): a. Sub-phylum: Sarcodina (Amoebae): i. Parasitic Amoeba. ii. Free-living Amoeba. b. Sub-phylum: Mastigophora (Flagellates): i. Intestinal and uro-genital flagellates e.g. Giardia intestinalis, Dientamoeba fragilis (Amoeba-like flagellate), and Trichomonas vaginalis. ii. Blood and tissue (haemo-somatic) flagellates: Leishmania and Trypanosoma species. 2. Phylum: Ciliophora, e.g. Balantidium coli. 3. Phylum: Apicomplexa (Sporozoa or Coccidia), e.g. Plasmodium, Toxoplasma gondii, Cryptosporidium parvum, Cystoisospora belli and Cyclospora cayetanensis.  Entamoeba histolytica Disease: Amoebiasis Mode of locomotion : Pseudopodia (false feet) Geo. Dis.: cosmopolitan, but more common in tropical and subtropical countries and in countries with poor sanitation Habitat: in the lumen of the large intestine (it is pathogenic because it can invade the wall of intestine) Reservoir: major: humans minor: dogs, pigs, monkeys  Entamoeba histolytica Morphology: 2 forms Cyst Trophozoite Infective stage: in polluted water Pathogenic stage: give and in infected food pathology as a result of infection  Life cycle: Cyst: infective Inters mouth through stage contaminated food, drink, To L.I. lumen and change fly, or through using human into trophozoite stool as fertilizer (pathogenic stage) Can do erosion through B.V. Produce lytic enzymes to liver and (capable of doing lysis other organs Flask shape and produce ulcer) ulcer Clinical picture: Dysentery: blood+mucous diarrhea (as a result of flask shape ulcer wall invasion) Sever abdominal pain Tenesmus: sense of incomplete evacuation (the patient at this point should be seeking medical advice) Complication: A. intestinal: peritonitis, appendicitis, Hemorrhage B. Extra intestinal: Most commonly: liver hepatitis (sever right abdominal pain) Fever amoebic liver abscess (sever pathology in the liver because the inflammation spots came together) shoulder pain and Toxemic manifestations Also in lung, skin, and brain  Plasmodium sp. (Malaria) Approximately 300 million people worldwide are affected by malaria and between 1 and 1.5 million people die from it every year Geo. Dis.: Previously extremely widespread, the malaria is now mainly confined to Africa, Asia and Latin America The problems of controlling malaria in these countries are aggravated by inadequate health structures and poor socioeconomic conditions. The situation has become even more complex over the last few years with the increase in resistance to the drugs normally used to combat the parasite that causes the disease. Causative agent: Malaria is caused by protozoan parasites of the genus Plasmodium. Species of Plasmodium are:  Plasmodium falciparum the most widespread and dangerous of the four, if untreated it can lead to fatal cerebral malaria.  Plasmodium vivax.  Plasmodium ovale.  Plasmodium malaria.  Plasmodium sp. (Malaria) Transmission: Malaria parasites are transmitted from one person to another by the female Anopheles Mosquito. The males do not transmit the disease as they feed only on plant juices. Reproduction: 1. Sexually reproduction: in anopheles mosquito 2. Asexual reproduction: in human (called sporozoans) in which sporozones multiply to produce merozoites, these, in turn, become trophozoits.  Life cycle: Mosquito bite Plasmodium sporozoits are carried by After 9-16 days they return develops in the gut of blood to the victim's liver to the blood and penetrate mosquito and is where they form cyst-like the red cells, where they passed on in the structure containing multiply again, saliva of an infected thousands of merozoits progressively breaking insect down the red cells This induces bouts of fever and anemia in the infected individual. In cerebral malaria, the infected red cells obstruct the blood vessels in the brain. Other vital organs can also be damaged often leading to the death of the patient.  Plasmodium sp. (Malaria) Pathology and clinical significance: When merozoits invade the blood cells, using hemoglobin as a nutrient, eventually, the infected red cells rupture, releasing merozoits that can invade other erythrocytes. If a large numbers of red cells rupture at roughly the same time, a paroxysm (sudden onset) of fever can result from the massive release of toxic substance. Plasmodium falciparum is the most dangerous species. P. malriae, P. vivax, and P. ovale cause milder form of the disease, probably because they invade either young or old red cells, but not both. This is in contrast to P. falciparum, which invades cells of all ages. Plasmodium falciparum is characterized by persistent high fever and orthostatic hypertension. Infection can lead to capillary obstruction and death if treatment is not introduced.  Toxoplama gondii Disease is called “Toxoplasmosis” Geo. Dis.: world wide Transmission: (1) eating row, undercooked meat of sheep and cow containing viable trophozoits (bradyzoits) (2) swallowing food and water contaminated with infected cat feces (3) Congenital transmission, through placenta (fatal) especially when infection occurs during pregnancy (4) person to person: ex. By blood transfusion or organ transmission Clinical symptom: -Infection of normal human hosts are common and usually asymptomatic -The infection can be very sever in immunocompromised individuals, who may also suffer recrudescence (relapse) of the infection. -Congenital infections can also be sever, and they are the major cause of blindness in newborns.