Medically Important Parasites PDF

Medically important parasites Asst. Prof. Ayhan MOEHMETOĞlu [email protected]  Parasites Parasites occur in two distinct forms: Single-celled protozoa and Multicellular metazoa called helminths or worms. 2 ...

Medically important parasites Asst. Prof. Ayhan MOEHMETOĞlu [email protected]  Parasites Parasites occur in two distinct forms: Single-celled protozoa and Multicellular metazoa called helminths or worms. 2  Protozoa For medical purposes, protozoa can be subdivided into four groups: Sarcodina (amebas), Sporozoa (sporozoans), Mastigophora (flagellates), and Ciliata (ciliates). 3  Metazoa Metazoa are subdivided into two phyla: The Platyhelminthes (flatworms) Cestoda (tapeworms) Trematoda (flukes). The Nemathelminthes (roundworms, nematodes). 4 Dr. Ayham Abulaila 5  Definitions, Types of Hosts Definitive host - the host in which sexual maturity and reproduction takes place. Intermediate host - the host in which the parasite undergoes essential development. Reservoir (carrier) host - the host harboring a parasite in nature, serving as a source of infection for other susceptible hosts. Reservoir hosts show no sign or symptom of disease. Vector - “carrier” of a parasite from one host to another. Often an insect.  Intestinal & Urogenital Protozoa (Entamoeba histolytica )  Entamoeba Diseases: Entamoeba histolytica causes amebic dysentery and liver abscess. The life cycle of E. histolytica has two stages: the motile ameba (trophozoite) and the nonmotile cyst 8  Entamoeba histolytica—Cyst. Arrow Entamoeba histolytica—Trophozoite. points to a cyst of Entamoeba histolytica. Long arrow points to trophozoite of Two of the four nuclei are visible just to Entamoeba histolytica. Short arrow points the left of the arrowhead. Provider: CDC. to the nucleus of the trophozoite. Arrowhead points to one of the six ingested red blood cells. Provider: CDC. Dr. Ayham Abulaila 10  Clinical Findings Acute intestinal amebiasis presents as dysentery (i.e., bloody, mucus-containing diarrhea) accompanied by lower abdominal discomfort, flatulence, and tenesmus. Chronic amebiasis with low-grade symptoms such as occasional diarrhea, weight loss, and fatigue also occurs. Amebic abscess in the liver 11 Giardia lamblia 12  Important Properties The life cycle consists of two stages, the trophozoite and the cyst The trophozoite is pear-shaped with two nuclei, four pairs of flagella, and a suction disk with which it attaches to the intestinal wall. 13 14  Clinical Findings Watery (nonbloody), foul-smelling diarrhea is accompanied by nausea, anorexia, flatulence, and abdominal cramps persisting for weeks or months. There is no fever. 15 Trichomonas 16  Trichomonas vaginalis Trichomonas vaginalis: causes trichomoniasis. T. vaginalis is a pear-shaped organism with a central nucleus and four anterior flagella. It has an undulating membrane that extends about two-thirds of its length. It exists only as a trophozoite; there is no cyst form. 17 18 Dr. Ayham Abulaila 23  Clinical Findings In women, a watery, foul-smelling, greenish vaginal discharge accompanied by itching and burning occurs. Infection in men is usually asymptomatic, but about 10% of infected men have urethritis. 20 21 Blood & Tissue Protozoa Plasmodium  Disease Malaria is caused by four plasmodia: Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium falciparum. P. vivax and P. falciparum are more common causes of malaria than are P. ovale and P.malariae. Worldwide, malaria is one of the most common infectious diseases and a leading cause of death. 28  Important Properties The vector and definitive host for plasmodia is the female Anopheles mosquito (only the female takes a blood meal). There are two phases in the life cycle: the sexual cycle, which occurs primarily in mosquitoes, and the asexual cycle, which occurs in humans, the intermediate hosts. The sexual cycle is called sporogony because sporozoites are produced, and the asexual cycle is called schizogony because schizonts are made. 29  Epidemiology More than 200 million people worldwide have malaria, and more than 1 million die of it each year, making it the most common lethal infectious disease. It occurs primarily in tropical and subtropical areas, especially in Asia, Africa, and Central and South America. 31 Dr. Ayham Abulaila 32  Human Toxoplasmosis Toxoplasmosis is a zoonotic disease Caused by Coccidian protozoan Toxoplasma gondii Infectes a wide range of animals, birds but does not appear to cause disease in them Toxoplasmosis can be transmitted transplacentally resulting in a spontaneous abortion, a still born, or a child that is severely handicapped mentally and/or physically. Trypanosoma cruzi 30  Disease and Important Properties T. cruzi is the cause of Chagas' disease (American trypanosomiasis). The life cycle involves the reduviid bug (Triatoma, cone- nose or kissing bug) as the vector. 31 Trypanosoma gambiense & Trypanosoma rhodesiense Sleeping sickness 39  Disease and Important Properties These organisms cause sleeping sickness (African trypanosomiasis). They are also known as Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. The vector for both is the tsetse fly, Dr. Ayham Abulaila 34 Dr. Ayham Abulaila 35 Leishmania  Leishmaniasis Leishmania spp. Leishmaniasis is caused by unicellular, flagellate, intracellular protozoa belonging to the genus Leishmania Obligatory intracellular parasite Female sandflay (Phlebotomus spp) visceral leishmaniasis (VL, kala-azar) cutaneous leishmaniasis (CL) In Turkey 37 VL, 2300 CL per year 46,003 cases between 1990 and 2010 mucosal leishmaniasis (ML). 96% Sanliurfa, Adana, Osmaniye, Hatay, Diyarbakir, İel and Kahramanmaras 50% of CL cases reported in the last 20 years https://www.who.int/leishmaniasis/burden/Leishmaniasis_Turkey/en/ 49 Helminths  Trematodes Trematoda (flukes) and Cestoda (tapeworms) are the two large classes of parasites in the phylum Platyhelminthes. The most important trematodes are Schistosoma species (blood flukes), Clonorchis sinensis (liver fluke), and Paragonimus westermani (lung fluke). Schistosomes have by far the greatest impact in terms of the number of people infected, morbidity, and mortality. 52 Cestodes  Tapeworms Tapeworms consist oftwo main parts: a rounded head called a scolex and a flat body of multiple segments called proglottids Humans usually acquire the infection when undercooked flesh containing the larvae is ingested. There are four medically important cestodes: Taenia solium, Taenia saginata, Diphyllobothrium latum, and Echinococcus granulosus. Nematodes  Nematodes Nematodes (also known as Nemathelminthes) are roundworms with a cylindrical body and a complete digestive tract, including a mouth and an anus. The body is covered with a noncellular, highly resistant coating called a cuticle. Nematodes have separate sexes; the female is usually larger than the male. The male typically has a coiled tail. The medically important nematodes can be divided into two categories according to their primary location in the body, namely, intestinal and tissue nematodes. 49  The intestinal nematodes The intestinal nematodes include Enterobius (pinworm), Trichuris (whipworm), Ascaris (giant roundworm), Necator and Ancylostoma (the two hookworms), Strongyloides (small roundworm), and Trichinella. Enterobius, Trichuris, and Ascaris are transmitted by ingestion of eggs; the others are transmitted as larvae. As adults, these nematodes live within the human body, except for Strongyloides, which can also exist in the soil. 50  The important tissue nematodes The importanttissue nematodes 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. A fourth species is the guinea worm, Dracunculus, whose larvae inhabit tiny crustaceans (copepods) and are ingested in drinking water. 62 Dr. Ayham Abulaila 64  Refernces Lippincotts Illustrated Reviews Microbiology 3rd Edition by Richard A. Harvey Cynthia Nau Cornelissen_Ph.D Clinical and Diagnostic Virology (Canbridge, 2009) Jawetz Melnick & Adelbergs Medical Microbiology Review of Medical Microbiology and Immunology, Fourteenth Edition by Warren Levinson, MD, PhD. www.cdc.com  For any question [email protected] 66