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Tile Medical Parasitology Marketing Department Mon. Feb. 21. 2018 Parasitology is the science dealing with parasites. Parasites can be classified into: 1. Helminthes. 2. Protozoa. 3. Arthropods. Medical terms you should know Parasite: is a living organism that lives at the expense of its host. Host:...

Tile Medical Parasitology Marketing Department Mon. Feb. 21. 2018 Parasitology is the science dealing with parasites. Parasites can be classified into: 1. Helminthes. 2. Protozoa. 3. Arthropods. Medical terms you should know Parasite: is a living organism that lives at the expense of its host. Host: the living organism at which the parasite lives on his expense. Parasitism: relationship between two living organisms one gets the benefit (parasite) and the other looses (host). As regard to the host Definitive (final host): The host that harbors the adult or sexual stages of the parasite. Intermediate host: The host that harbors the larval or asexual stages of the parasite. Vector: an arthropod the carries the infective stage of the parasite and can transmit it by active biological sharing in life cycle. Reservoir hosts: other hosts that harbor the parasite and thus ensure continuity of the parasite's life cycle and act as As regard to parasite Obligate parasite is termed when the parasite can live only in a host. Facultative parasite when it can live both in a host as well as in free form. Endoparasites parasites that live inside the body. Ecto-parasites parasites that exist on the body surface. Parasite life cycle The whole process of growing and developing e f i y l t nl c e o t. r i : D cl e o s h y c ne o In di cy rec lif cle t l e : t i fe c in yc he th mo le i an re s (in ho on te st e at rm e ed a fi n i ho nal d st s). Mode of parasitic infection 1. Food and drink: containing the infective stage of the parasite (entamaeba histolytica and giardia). 2. Soil, dust and water: a. Ingestion of food or drink contaminated with soil contain the infective stage of the parasite. b. Inhalation of dust. c. Direct contact with soil: handling or walking barefooted, so the infective stage present in the soil can penetrate the skin (Ancylostoma duodenale). d. Using water streams for swimming, washing or irrigation, so the infective stage present in the water can penetrate the skin (S. haematobium). 3. Vector: a. Bite of the vector inoculating the infective stage (Sporozoites of malaria placed by Mosquito). b. Contamination of the intact or wounded skin with the feces of the vector containing the infective stage (Trypanosoma cruzi). c. Direct penetration of an arthropod to the skin. 4. Direct contact: d. Skin contact (Scabies). e. Sexual contact. f. Autoinfection. 5. Congenital: maternal–fetal (Toxoplasma gondii) Effect of the parasite on the host Abstractin Abstractin g g nourishm nourishm ent ent from from the the host host Mechanical Mechanical effect effect due due to to pressure pressure or or obstruction; obstruction; feeding feeding on on the the tissues tissues or or irritation irritation of of the the tissues tissues leads leads to to inflammatory inflammatory or or neoplastic neoplastic reactions. reactions. Toxic Toxic effect effect from from the the toxins toxins or or the the waste waste products. products. Second Second ary ary infectio infectio n. n. The host reaction to the invading parasite Generalized in the form of fever, anaemia, eosinophilia, weakness. Localized according to tissue or organ affected. BMC Protozoa Protozoa General characters of protozoa Unicellular organisms that are capable of performing whole life functions. Eukaryotic. Complex life cycle involving various stages or forms Reproduction : sexual and asexual Motility : flagella, cilia, amoeboid movement These ways of motility are used to divide them into taxonomic The active feeding and growing stage of the protozoa is called the trophozoite. Several species possess a resting or resistant cystic stage which enables prolonged survival under unfavourable conditions. cyst is usually the infective stage Cyst formation Encystment of some protozoa is essential for survival outside the body and during Classification and motility The main phyla of medical importance Sarcomastigophora: containing amoebae and flagellates, division is by binary fission and locomotion by pseudopodia (ameobae) or whip like flagellar movement (flagellates). Ciliophora: the ciliates which divide by binary fission or conjugation and the locomotion is by cilia. Apicomplexa: containing the Sporozoa which are intracellular protozoa with complex life cycle (sexual and asexual reproduction). Microspora Protozoal infections in humans Phylum Organism Disease Habitat/source/ vector Sarcodina (amoeba) Entamoeba histolytica Amoebic dysentery Contaminated Water , food or autoinfection Mastigophora (flagellates) Giardia intestinalis Giardiasis Trichomonas vaginalis Trypanosoma brucei Vaginosis Contaminated Water Vagina Sleeping sickness Tsetse fly Trypansoma cruzi Chagas disease Kissing bug Leishmania spp Vesceral & Cutaneous Leishmaniasis sandflies Ciliophora (Ciliates) Balantidium coli Balantidial dysentery Contaminated Water, food or autoinfection Sporozoa (Apicomplexans) Plasmodium spp Malaria Toxoplasma gondii Toxoplasmosis Cryptosporidium Diarrhoea Microsporidium Diarrhoea Anopheles Mosquito Raw meat, cat faeces Humans, animals Humans, animals BMC Intestinal protozoa Entamoeba histolytica Diseases Amebic dysentery and liver abscess. Morphology: it has two form stages Trophozoite: A: Entamoeba With the ameboid appearance due to presence histolytica trophozoite with one ingested red of pseudopodia. Cyst: cysts are spherical with a cyst wall. 1 to 4 nuclei which are similar to trophozoite. blood cell and one nucleus (circle with inner dotted line represents a red blood cell). B: E. histolytica cyst with four Life cycle There are: no intermediate or reservoir hosts. infective stage: mature cysts. Mode of infection: feco-orally through contaminated food or hands. Clinical Findings # Dysentery. Amebic abscess Laboratory diagnosis Finding cysts in the stool. # Gardia lamblia Diseases Gardiasis= Lambliasis. Morphology Trophozoite: half pear-shaped organism with 8 flagella. There are two anteriorly located large suction discs. The cytoplasm contains two nuclei Cyst: The cytoplasm contains four nuclei with smooth well-defined wall. Life cycle Definitive host: Man. Infective stage: cyst Mode of infection: ingestion of cysts Clinical finding steatorrhia Laboratory diagnosis Cysts (constipation) and trophs ( diarrhea) in the stool. BMC Urogenital protozoa Trichomonas vaginalis (a flagellate) Disease: Trichomoniasis Morphology Trophoziote is the active and infective form, no cyst stage. Symptoms In Females with heavy infection: copious foul-smelling yellowish, frothy discharge. Life cycle Infective stage: trophozoites Infection occurs primarily via sexual contact. BMC Blood & Tissue protozoa Plasmodium Disease Malaria is caused by four plasmodia: Plasmodium vivax. Plasmodium ovale. Plasmodium malariae. Plasmodium falciparum. malaria is one of the most common infectious diseases and a leading cause of death. Life cycle There are two phases in the life cycle: 1. the sexual cycle in mosquitoes, the final host. 2. asexual cycle “schizogony”, occurs in humans, the intermediate hosts. Infective stage: sporozoites (mosquito) and schizonts (blood) Mode of infection: 1. Mosquito bites. 2. Across the placenta. 3. Blood transfusions. 4. Intravenous drug abuse. Pathogenesis Most of the pathologic findings of malaria result from the destruction of red blood cells. Malaria presents with abrupt onset of fever and chills. The timing of the fever cycle is 72 hours for P. malariae (quartan malaria) and 48 hours for the other plasmodia (tertian malaria). Malaria caused by P. falciparum is more severe than that caused by other plasmodia because: 1. It is characterized by infection of more red cells. 2. Occlusion of the capillaries with aggregates of parasitized red cells leading to:  Cerebral malaria.  Hemoglobinuria "black water fever”. Laboratory Diagnosis Blood films for finding the parasite inside RBCs Toxoplasma Disease Toxoplasma gondii causes toxoplasmosis. Life cycle Infective stage 1. Oocysts in animal stools. 2. True cysts in meat. 3. Tachyzoites in blood or transplacentally. Mode of transmission 1. Ingestion of cysts in uncooked meat or cat feces. 2. Ingestion of oocysts through contaminated hands with animal stool. 3. Transplacental transmission: congenital infection of the fetus occurs only when the mother is infected during pregnancy for the 1st time. Clinical Findings Asymptomatic in immunocompetent adults. Immunosupressed patients (e.g., AIDS patients), life-threatening disseminated disease. Congenital infection. Laboratory Diagnosis Immunofluorescence assay for IgM antibody is used. IgM is used to diagnose congenital infection, because IgG can be maternal in origin. BMC Helminthes 3 main classes of medically important helminthes 1. The Nematodes 2. The Trematodes Trematoda Cestoda 3. The Cestodes Nematoda Flattened, leaflike, Bilaterally symmetrical, not segmented Flattened, ribbon - Elongated. Shape shaped & cylindrical, round segmented in cross section & not segmented Simple blind tube(no anus) Absent Simple straight tube with anus Digestive system Absent Absent Present Body cavity Hermaphrodite (except schistosoma) Hermaphrodite separate Gender(Sex) BMC Trematodes Schistosoma (Blood fluke) Disease: Schistosomiasis (Bilharziasis). It differs from other trematodes in : 1. Separate sexes. 2. Eggs with spine. 3. Cercaria is the infective stage. 3 known schistosomes infect humans: 4. S. haematobium 5. S. mansoni: 6. S. japonicum S.mansoni : mesenteric venules of bowel &, rectum. It causes intestinal schistosomiasis and eggs pass in stool. S. haematobium: venous plexus of the bladder, Life cycle Intermediate host is a snail S. heamatobium (Bulinus trancatus) S. mansoni (Biomphalaria alexandrina). Infective stage: is the cercaria Mode of infection: Penetration of the cercaria (which is attracted to man by the body temperature) to skin when water begins to dry. Clinical features Urinary bilhariziasis: terminal haematuria. Intestinal bilhariziasis: dysentery. Laboratory diagnosis: Detection of eggs in stools or urine. BMC Cestoda General characters of cestodes Body is formed of: Scolex: with organs of fixation either in form of bothria, suckers and hooks. Neck: part of the warm that will give rise to segments. Strobila: it is formed of segments. Immature segments: sexual organs are not will developed. Mature segments: with fully developed sexual organs. Gravid segments: the egg engorged uterus covers the other structures. Taenia saginata (beef tapeworm) Disease: taeniasis saginata. Morphology: Has a scolex. Segmented from 1000-2000 segments. 1. Immature segments. 2. Mature segments. 3. Gravid segments. Clinical finding #Intestinal obstruction#Loss of weight as the parasite consumes much of patient’s food. Life cycle: Definitive host: human. Intermediate host: cattle (beef). Infective stage: Cysticercus bovis. Mode of infection: ingestion of raw or improperly cooked beef containing the cysticercus bovis. Ingestion of eggs is not infective to human. Diagnosis Detection of the eggs or gravid segments in stool. T. solium is the same as T. saginata but. Intermediate host is the Pork Eggs could be infective to human leading to cysticercosis. Taenia solium (Pork tapeworm) Same as T. saginata. 2-6 m Morphological differences: 1. Hooked scolex. 2. Gravid segments are less in size and in branches. Intermediate host is the Pork Occurring in pork-eating countries. The infective stage is cysticercus cellulosa. Eggs could be infective to human leading to cysticercosis. Cysticercosis The presence of cysticercus cellulosae (the larval stage of T. solium) in human tissues. Infection occurs after ingestion of the T. solium eggs through: 1. Contaminated food or water. 2. Autoinfection: patients having adult worm may be complicated with cysticercosis (external) along contaminated fingers (from anus to mouth), (internal) by reversed peristalsis. Symptoms depend on number, size & site of larvae: (1) Subcutaneous type: The subcutaneous nodules are usually found in head, limbs, neck, abdomen and back. They are movable and painless. (2) Muscle type Note this cysticercus in the tongue (3) Ocular type: The cysticercus is usually found in the vitreous body or subretina. Visual disturbance often occurs. The died body of worm may provokes local inflammation causing blindness. (4) Cerebral cysticercosis BMC Nematodes Enterobius vermicularis (pinworm) Disease: pinworm infection (enterobiasis). Life cycle: Infective stage: Egg. Mode of infection: ingesting of the worm eggs. At night, the female migrates from the anus and releases thousands of fertilized eggs on the perianal skin and into the environment. Clinical Findings Perianal pruritus is the most prominent symptom. Diagnosis The eggs are recovered from perianal skin by using the Scotch tape technique and can be observed microscopically (Figure 56–3). Unlike those of other intestinal nematodes, these eggs are not found in the stools. Ascaris lumbricoides Disease: ascariasis Life cycle: Infective stage: egg. Mode of infection: ingesting eggs in food or water contaminated with human feces Clinical Findings Most infections are asymptomatic Malnutrition and intestinal obstruction in a heavy worm burden patient. Laboratory Diagnosis Microscopically by detecting eggs in the stools. Treatment Both mebendazole and pyrantel pamoate are effective. Ancylostoma duodenale (hookworm) Disease: Ancylostomiasis. Life cycle: Infective stage: filariform larvae. Mode of infection: penetration of the skin by the filariform larvae on walking with bared foot on moist soil. Clinical Findings loss of blood at the site of attachment in the small intestine will lead to microcytic aneamia. Laboratory Diagnosis Microscopically by finding eggs in the stools. Wuchereria Disease: W. bancrofti leads to elephantiasis. Vector: female mosquito (especially Anopheles and Culex species). Infective stage: infective larvae. Mode of infection: Humans are infected when the female mosquito deposits infective larvae on the skin while biting. Clinical Findings Adult worms in the lymph nodes cause inflammation that eventually obstructs the lymphatic vessels, causing edema. Massive edema of the legs is called elephantiasis. Laboratory Diagnosis Thick blood smears taken from the patient at night reveal the microfilariae. Treatment Diethylcarbamazine. Thank You