Basic Concepts of Parasitology, Pathogenesis, and Diagnosis of Parasitic Infections Class 1 2024-2025 PDF

BASIC CONCEPTS OF PARASITOLOGY- PATHOGENESIS AND DIAGNOSIS OF PARASITIC INFECTIONS BEDİA DİNÇ  single-celled protozoa multicellular metazoa called helminths or worms For medical purposes, protozoa are classified according to their most important site of infection;...

BASIC CONCEPTS OF PARASITOLOGY- PATHOGENESIS AND DIAGNOSIS OF PARASITIC INFECTIONS BEDİA DİNÇ  single-celled protozoa multicellular metazoa called helminths or worms For medical purposes, protozoa are classified according to their most important site of infection; the intestinal protozoa such as Giardia, the urogenital protozoa such as Trichomonas, the blood protozoa such as Plasmodium (the cause of malaria), tissue protozoa such as Toxoplasma. DEFINITIONS trophozoite, which is the motile, feeding, reproducing form surrounded by a flexible cell membrane, cyst, which is the nonmotile, nonmetabolizing, nonreproducing form surrounded by a thick wall. The cyst form survives well in the environment and so is often involved in transmission.  ****Certain protozoa, such as Leishmania and Trypanosoma, have flagellated forms called promastigotes or trypomastigotes nonflagellated forms called amastigotes.  Transmission of the intestinal protozoa typically occurs by ingestion of cysts, Transmission of the blood protozoa occurs via insect vectors such as the mosquito in the case of Plasmodium (malaria), the reduvid bug in the case of Trypanosoma cruzi (Chagas’ disease), the tsetse fly in the case of Trypanosoma brucei (sleeping sickness), the sandfly in the case of Leishmania donovani (visceral leishmaniasis or kala-azar) HELMINTHS NEMATODES Nematodes (roundworms) have long thin unsegmented tube-like bodies with anterior mouths and longitudinal digestive tracts. They have a fluid-filled internal body cavity which acts as a hydrostatic skeleton providing rigidity. Worms use longitudinal muscles to produce a sideways thrashing motion. Adult worms form separate sexes with well- developed reproductive systems. NEMATODES TREMATODES Trematodes (flukes) have small flat leaf-like bodies with oral and ventral suckers and a blind sac-like gut. They do not have a body cavity and are dorsoventrally flattened with bilateral symmetry. They exhibit elaborate gliding or creeping motion over substrates using compact 3-D arrays of muscles. Most species are hermaphroditic (individuals with male and female reproductive systems) although some blood flukes form separate male and female adults. TREMATODES CESTODES Cestodes (tapeworms) have long flat ribbon-like bodies with a single anterior holdfast organ (scolex) and numerous segments. They do not have a gut and all nutrients are taken up through the tegument. They do not have a body cavity and are flattened to facilitate perfusion to all tissues. Segments exhibit slow body flexion produced by longitudinal and transverse muscles. All tapeworms are hermaphroditic and each segment contains both male and female organs. CESTODES  Helminths form three main life-cycle stages: eggs, larvae, adults. The egg contains an embryo that, upon hatching, differentiates into a larval form, which then matures into the adult form that produces the eggs.  Transmission occurs by three main modes: ingestion of eggs (T. solium, Enterobius, Ascaris), penetration of the skin by larvae (Schistosoma, hookworms, Strongyloides), insect bite (Wuchereria, Onchocerca, Dracunculus). LIFE CYCLE This may involve Passing through a number of developmental stages & enviroment Parasitic and non-parasitic stages. The life of a parasite can be divided into a number of phases: Growth and maturation, Reproductive (sexual and asexual) and Transmission phases. All vitally important for the successful survival of the parasite. *****Can be simple or complex depending on how many different hosts it requires to complete its cycle  Why study life cycles? Break the chain!!! Control. Treatment. Epidemiology. Fundamental research. DEFINITIONS Definitive host: harbors the adults or final stages or sexual stages (♂♀) in the development of parasite,may be a human or any other living organism. Example: Mosquito acts as a definite host for Plasmodium spp. in Malaria. Intermediate host: in which you have the larva stages or intermediate stages in the development. Example: Man acts as an intermediate host for Plasmodium spp. in Malaria. Reservoir/Temporary 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. Example: Dog is the reservoir host for disease kala azar. How do Parasites Cause Inquiry to their Host? Competition for the host’s nutrients - Eg. D.latum absorbs vitamin B-12, can cause anemia - other tapeworms absorb large amounts of proteins and sugars Use of host’s fluids - hookworm ingests blood, can be up to 250 ml/day Destruction of host tissues - some injure upon entry, some after established - eg. Swimmers itch, cercariae penetrate and cause inflammation - intestinal worms, after established cause small lesions in gut, possible secondary infection - Entamoeba actively digest epithelial cells in large intestine  Tissue changes - may cause serious consequences to host - hyperplasia,. Eg Fasciola - hypertrophy, - metaplasia, change of tissue cell type to another type. Eg. Paragonims (lung fluke) - neoplasia, growth of cell to form a new structure. Eg. Tumors  Toxins and secretions - some may cause pathogenic response, some may inhibit immune function - eg. Mosquito saliva Mechanical interference - Elephantiasis (filarial worms) blocks lymphatic system - Tapeworms in large numbers can block intestine - Plasmodium can cause RBC’s to stick together and clog capillaries Host Responses Nonspecific immunity Macrophage endocytosis Common for bacteria and small protozoa Inflammation Acute – edema and increase of leukocytes Subacute – monocytes and lymphocytes present, with fibrocytes binding parasite with collagen. Chronic – plasma cells present and form a granuloma Hyperplasia – parasite causes host to produce more cells Liver fluke simulating enlargement of bile duct Neoplasia (cancer) – rare parasites have been associated with cancer, but mechanisms are still unknown. Host Responses Specific Immunity Humoral response: Formation of immunoglobulins(Ig) by B cells. IgE fights helminths (high IgE levels!!) IgM and IgG important against protozoans Cell mediated response: uses T-cells Cytotoxic T cells inject invading parasites Also release cytokines, which promote nonspecific immunity. Parasite Responses Antigenic variation Change surface glycoproteins regularly Being poorly antigenetic Don’t induce a response, or a most a mild one Hide within host cells Host can’t kill what it can’t find Camouflage Use bits of host cells and attach to parasite’s surface Depress host’s immune response Modulate produce of host T cell production LABORATORY DIAGNOSIS OF PARASITE INFECTIONS Samples for detection Blood Urine Stool Biopsy /aspirate CSF Sputum METHODS Macroscopic examination Microscopy Serology Rapid tests Culture Molecular techniques Xenodiagnosis MACROSCOPIC EXAMINATION Stool specimen can be examined with the naked eye for presence of some adult worms Ascaris Taenia species E.vermicularis MICROSCOPY The majority of intestinal, blood, urinary and skin parasites are usually detected microscopically Use different body specimen such as blood, stool, urine, CSF etc either directly or following concentration techniques in stained or unstained preparation  Temporary stain; Eosin, Lugol’s iodine solution, Acridin orange Permanent stain; Giemsa, Trichrome stain, Modified ziehl-nielsen stain SEROLOGY parasite antigen (in various samples) antibodies produced as a result of parasitic infection (in serum). Serological tests are used in cases of…. Parasites live in the tissue of internal organ and can not easily obtained for examination. Parasites can be found in specimens only in certain stages of infection, e.g., in the acute stage not in the chronic stage. Parasites are present intermittently or in too few numbers to be easily detected in the specimens. The techniques used to detect parasites are complex or time consuming. SEROLOGICAL TESTS South American trypanosomiasis , Chronic stage African trypanosomiasis, when parasitaemia is low Leishmaniasis Filariasis Amoebic liver abscess Trichinosis Toxoplasmosis Toxocariasis Hydatid disease Schistosomiasis Malaria RAPID TESTS Rapid diagnostic tests (RDTs) have the potential to greatly improve the quality of management of infections, especially in remote areas with limited access to good quality microscopy services CULTURE Growth medium is provided for a specific parasite. NNN Medium: (Novy-Mac Neal-Nicolle) for Leishmania spp Usually not used for routine diagnosis MOLECULAR TECHNIQUES PCR The purpose of a PCR is to make a huge number of copies of a gene of the parasite. Commonly used for diagnosis of; Toxoplasmosis Malaria Giardiasis Leishmaniasis Other specimens examined for intestinal parasites Duodenal aspirates - e.g., Strongyloides sp., Giardia lamblia Sigmoidoscopy specimens - e.g., ameba, Cryptosporidium Urine - Schistosoma hematobium & Enterobius vermicularis ova Cellophane tape-Enterobius vermicularis ova Other specimens-II Vaginal/urethral discharge Trichomonas vaginalis trophozoites Sputum Strongyloides larvae Paragonimus westermani eggs Entamoeba histolytica (from pulmonary abscess) Detection of blood parasites Two types of blood films can be made, Thick films Thin films Parasites that could be detected in blood film Malaria Trypanosoma (African and American). Microfilaria of all types Filaria except Onchocerca volvulus. Indian type of Leishmania donovani. XENODIAGNOSIS Xenodiagnosis is a diagnostic method used to document the presence of infectious disease microorganisms or pathogens by exposing possibly infected tissue to a vector and then examining the vector for the presence of the microorganisms or pathogens it may have ingested. Trypanosoma cruzi infection  THANK YOU….