Parasites Lecture 5 PDF

Parasites  Classification of parasites Parasites Protozoa Helminthes Blood and Intestinal Urogenital Cestodes Trematodes Nematodes...

Parasites  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 Trichomonas Giardia lamblia Trypanosoma Vaginalis Cryptosporidium Leishmania  Protozoa Protozoa are unicellular, eukaryotic organisms Protozoa inhabit water and soil Have a life cycle consisting of a trophozoite and cyst Protozoa reproduce asexually by fission, budding, or schizogony Some protozoa are part of the normal microbiota of animals Of the nearly 20,000 species of protozoa, relatively few cause human disease. Malaria is the fourth leading cause of death in children in Africa.  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 has not been affected. Parasitism: When the other organism become affected  Hosts 1. Intermediate host - a host in which either eggs (usually ingested) or very early larval forms develop into larval or intermediate parasite. one in which the asexual cycle occurs or the larva is present 2. Definitive host - a host in which the larval stages infect and mature into the sexually mature adult parasites. one in which the sexual cycle occurs or the adult is present 3. A reservoir host is any host essential to parasite survival and a focus for spread to other hosts.  Vectors Mechanical vectors - are nonessential to the life cycle of the pathogen (e.g., flies who track Chlamydia trachomatis from one child’s eye to another). Biological vectors - serve as the site of some developmental events in the life cycle of the parasite, such as mosquitoes in malaria. PROTOZOAN PARASITES Amebas - move by pseudopods include Entamoeba, Acanthamoeba, and Naegleria. Flagellates move by the action of flagella and include Giardia, Trichomonas, Trypanosoma, and Leishmania. Ciliates move by the action of cilia. Sporozoa (also or coccidia) are intracellular protozoans with complex lifecycles and non motile. They include Plasmodium, Toxoplasma, etc. Entamoeba histolytica Disease: Amoebiasis Mode of locomotion : Pseudopodia Geo. Dis.: cosmopolitan, but more common in tropical and subtropical countries and in countries with poor sanitation Pathogenic E. histolytica – uses lectins, non-pathogenic E. dispar 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 of liver and Produce lytic enzymes other organs (capable of doing lysis Flask shape and produce ulcer) ulcer Clinical picture: Dysentery: blood+mucous diarrhea (as a result of flask shape ulcer wall invasion) Sever abdominal pain 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) Also in lung, skin, and brain 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) Life Cycle of Plasmodium Toxoplama gondii Disease is called “Toxoplasmosis” Geo. Dis.: worldwide Transmission: (1) eating row, undercooked meat containing viable trophozoits. (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 transplantation Clinical symptom: -Infection of normal human hosts are common and usually asymptomatic -The infection can be very severe in immunocompromised individuals -Congenital infections can also be severe, and they are the major cause of blindness in newborns.  Trypanosoma Trypanosomiasis West African East African American Trypanosomiasis Trypanosomiasis Trypanosomiasis T. brucei bambiense T. brucei rhodesiense T. cruzi Chagas’ Disease Sleeping Sickness Transmitted by Tsetse fly Transmitted by Kissing Bug Features of Medically Important Protozoa Medically Important Stages in Life Cycle of Intestinal Protozoa  Helmints Helminths are multicellular eukaryotic animals that generally possess digestive, circulatory, nervous, excretory, and reproductive systems. Platyhelminthes (flatworms) Nematoda (roundworms) Cestodes Taenia Taenia saginata (Beef tapeworm) Taenia solium – human is a definitive host (Pork tapeworm) Diphyllobothrium Broad fish tapeworm Echinococcus – human is an intermediate host (Dog tapeworm)  Taenia saginata or Beef Tape-Worms habitat is the small intestine—the ileum Transmission: acquired in humans through the ingestion of raw or poorly cooked meat of infected cows. These cows have been infected via the ingestion of human feces containing the eggs of the parasite Morphology: Adult is divided into three parts, 1- a head: round and small. It has four suction disks 2- neck: A small, slender neck, about an inch long 3- number of segments. Adult tapeworms and can grow up to 25 meters in the lumen of the intestine, but are usually closer to 5 meters in length Egg present in feces Life cycle of the tapeworm, Echinococcus spp. Features of Medically Important Cestodes (Tapeworms) TREMATODES - General Characteristics Flat, unsegmented worms Leaf-like organisms Incomplete digestive tract Schistosoma (blood flukes) Clonorchis (liver fluke) Paragonimus westermani (lung fluke).  Trematodes Bilharzia (Schistosomiasis) Disease of the venous system, acquired by people when they come in contact with contaminated water. Adult Schistosomes take up residence in various abdominal veins, depending on the species; they are, therefore called (Blood Flukes). Very common among children Geo. Dis.: developing countries, affects up to 200 million people Transmission: Direct skin penetration Fresh water becomes contaminated by Schistosoma eggs when infected people urinate or defecate in the water. The eggs hatch and the parasites grow and develop inside snails. Schistosoma is not acquired by ingestion of contaminated food, it directly penetrates the skin of swimmers in contaminated rivers and lakes. 2 types of Schistosomiasis: Intestinal Schistosomiasis Urinary tract Schistosomiasis  Bilharzia (Schistosomiasis) Pathology: Intestinal Schistosoma: the primary site of infection is the gastrointestinal tract. Damage to the intestinal wall is caused by the host’s inflammatory response to eggs deposited at that site. The eggs also secret proteolytic enzymes that further damage the tissue. Urinary tract Schistosoma: The primary site of infection are veins of the urinary bladder, where the organism eggs can induce fibrosis, granulomas, and hematuria Clinical picture: Intestinal Schistosoma: GI bleeding, diarrhea, and liver damage. Urinary tract Schistosoma: hematuria Disease: Bilharzia Intermediate host Features of Medically Important Trematodes Medically Important Stages in Life Cycle of Trematodes  Nematodes Round-worms with a cylindrical body and a complete digestive tract, including a mouth and an anus Have round unsegmented bodies Have separate sexes Their life cycle includes: egg, larvae and adult The medically important nematodes - intestinal and tissue nematodes. INTESTINAL NEMATODES Enterobius - pinworm Ascaris - giant roundworm Ancylostoma & Necator - hookworms Strongyloides - small roundworm Trichinella The pinworm, Enterobius vermicularis Ascaris lumbricoides (Roundworm) Ascaris lumbricoides is the largest nematode (roundworm) parasitizing the human intestine 1/3 the world population is infected with this worm Geo.dis.: worldwide, common among people with low standard of living and among children Morphology: Adult: in small intestine adult egg: infective stage Life cycle: 2 phases: lung and intestinal Egg ingested, hatches in duodenum; larvae penetrate intestine wall, enter blood vessels and embolize through liver to lungs. They then migrate into airspaces, up trachea and are swallowed, taking up permanent adult residence in the small intestine; ~ 2 months from egg to mature adult Each female produce 200,000 eggs per day Clinical symptoms: - related to number of worms; small numbers asymptomatic large numbers of adults in intestine – obstruction, pains - at times adults migrate into bile duct, - cause malnutrition if in large numbers Lung phase A. lumbricoides is known as Ascaris pneumonitis. In the lung it causes hemorrhage, inflammation, bacterial infection. It also causes allergy in areas with seasonal transmission. Typically occurs at 6–14 days after initial exposure. Intestinal phase The intestinal phase causes malnourishment, intestinal blockage. A. lumbricoides will move around in the body in response to chemotherapy or fever. Typically occurs at 6 to 8 weeks after initial exposure. TISSUE NEMATODES Wuchereria Onchocerca Loa Dracunculus Wuchereria, Onchocerca, and Loa are called the “filarial worms,” because they produce motile embryos called microfilariae in blood and tissue fluids. These organisms are transmitted from person to person by bloodsucking mosquitoes or flies. Dracunculus is the guinea worm, larvae inhabit tiny crustaceans (copepods) and are ingested in drinking water. Elephantiasis. References Levinson, Review of Medical Microbiology and Immunology, Part VI Gerard J. Tortora, Berdell R. Funke, Christine L. Case - Microbiology_ an introduction-Pearson (2018), Chapter 12