Single-celled Parasites (Protozoa) - Amebae PDF

Balantidium coli Single-celled parasites (Protozoa). Phylum Sarcomastigophora. Subphylum Sarcodina Leishmania donovani Entamoeba histolytica Trypanosoma gambiense Trichomonas hominis Plasmodium vivax Giardia lamblia Toxoplasma gondi Protozoa  Single-celled eukaryotic microorganisms belo...

Balantidium coli Single-celled parasites (Protozoa). Phylum Sarcomastigophora. Subphylum Sarcodina Leishmania donovani Entamoeba histolytica Trypanosoma gambiense Trichomonas hominis Plasmodium vivax Giardia lamblia Toxoplasma gondi Protozoa  Single-celled eukaryotic microorganisms belonging to kingdom Protista are classified as Protozoa. o Active feeding and growing stage of the protozoa is called the trophozoite. With are noted parasites, that will be studied by you in the course of parasitology. CLASSIFICATION Morphology of protozoa Balantidium coli ✓Nucleus – most protozoa have one nucleus, others – two (macro- and micronucleus) and more. Morphology of protozoa Balantidium coli ✓Cytoplasm – two layers – external (ectoplasm) and internal (endoplasm) Morphology of protozoa ✓Cytoplasm – ectoplasm is shrouded by a cell membrane, which in most protists is denser and is called the pellicle. When it is even denser, it performs a supporting and protective function, and then it is called the cuticle. Morphology of protozoa Giardia lamblia Balantidium coli ✓Cytoplasmic organelles – perform a variety of functions, for example - motor (pseudopods, flagella, cilia), reception and processing of food (cytostome, cytopharynx, food vacuoles), excretory function – contractile vacuoles. ✓Two forms: vegetative (trophozoite) and cystic (cyst) – no all single-celled parasites have cystic form! ✓The cyst serves for the survival of the parasite in adverse living conditions. ✓Cysts don’t move, feed and multiply. The cystic form is invasive form of some parasites (it can infect the host)! Types of reproduction of Protozoa: ✓asexual (binary fission, multiple fission, endodyogeny) ✓sexual (conjugation in Balantidium coli; gametogony in Sporozoa like genus Plasmodium)! In amoebae, division occurs along any plane, but in flagellates, division is along longitudinal axis and in ciliates, in the transverse plane. Phylum Sarcomastigophora  Includes two subphyla:  subphylum Mastigophora  subphylum Sarcodina - 7 species amoebae inhabit the gastrointestinal tract of man, as a parasite is only Entamoeba histolytica of the genus Entamoeba o their shape is variable or undetermined (no shell or internal skeleton) o move with pseudopods (false feet) Phylum Sarcomastigophora. Subphylum Sarcodina (amoebae) Entamoeba histolytica • Entamoeba histolytica is amoeba, parasitizing in large intestine of human. • While the majority of infected humans (80-99%) are asymptomatic, invasive amebiasis causes disabling illness in an estimated 50 million of people and causes 50,000 deaths annually, mostly in the tropical belt of Asia, Africa and Latin America E. histolytica is worldwide in prevalence, being much more common in the tropics than elsewhere. It has been found wherever sanitation is poor, in all climatic zones from Alaska to Straits of Magellan. Morphology E. histolytica occurs in three forms: 1. forma magna 2. forma minuta 3. forma cystica Forma magna: Irregular in shape An active-moving, feeding and growing stage Produces pseudopods (false feet organelles) – they are motor organelles Inhabits the human colon Phagocytose red blood cells Pathogenic form pseudopodes Morphology E. histolytica occurs in three forms: 1. forma magna 2. forma minuta 3. forma cystica Forma minuta: Lives in the lumen as a commensal, it is generally smaller in size Phagocytose bacteria and fungi from the intestinal contents, but never erythrocytes. Produces pseudopods Does not cause disease It can turn into forma magna or forma cystica Morphology E. histolytica occurs in three forms: 1. forma magna 2. forma minuta 3. forma cystica Forma cystica: Spherical in shape Immature cyst (1 or 2 nuclei) has the glycogen vacuole & chromatoid body. Inclusions disappear in mature cyst (4 nuclei) Does not produce pseudopodes Invasive form (it infect us)! chromatoid body glycogen vacuole Immature cyst Mature cyst Life cycle of E. histolytica  Man acquires infection by swallowing mature cysts with fecally contaminated food, water or hands. Life cycle of E. histolytica ➢ Excystation occurs in the small intestine: when quadrinucleatead amoeba is liberated from cystic wall, the nuclei immediately undergo division to form eight nuclei, each of which gets surrounded by its own cytoplasm to become eight small trophozoites (minuta forms) Life cycle of E. histolytica ➢ Adult trophozoites (minuta forms) migrate to the large intestine. The optimal habitat for E. histolytica is the submucosal tissue of large intestine, where they reproduce. Life cycle of E. histolytica ➢ In most of the cases (when the immunological resistance is optimal) E. histolytica remains as a commensal (forma minuta) in the large intestine without causing any ill effects. From the minute form in the infected person, the formation and secretion of cysts begins. These cysts get into the environment with feces and can infect other people. A person, excreting cysts, is called a cyst carrier. Life cycle of E. histolytica ➢ In people with reduced biological resistance of the body due to disease, intoxication forma minuta turns into forma magna, which causes local damages (ulcers in the intestine, hemorrhages) through the proteolytic enzymes separated from it. Forma magna can get into the bloodstream and reach other organs (most often liver, lungs and brain). The typical amebic ulcer is flask-shaped in cross section, with mouth and neck being narrow and base large and rounded. Clinical features The typical manifestation of intestinal amebiasis is amebic dysentery (amebiasis). Amebic colitis The expansion of ulcers in depth can lead to perforation of the intestinal wall Symptoms: ✓ bloody, mucus-containing diarrhea ✓ lower abdominal discomfort (colickly abdominal pain) ✓ the patient is usually afebrile (when the colitis is fulminant and there is colon necrosis, the patients is febrile) Clinical features Extraintestinal manifestations of amebiasis: abscesses in different organs (liver, brain, lung…) Symptoms depends on organ localization of abscess! Abscess in the liver Abscess: cavity filled with pus How can we diagnose amebiasis? 1. ▪ - Microscopy: stool examination: detection of cysts (typically found in formed stool) detection of forma magna (typically found in fresh, diarrheal stool) – rarely, because forma magna quickly perishes ▪ detection of trophozoite in organ biopsy (e.g liver) оr pus 2. Serology: ▪ antibody detection (test for antibodies in serum help in diagnosis of mainly extraintestinal localisations of amoeba) ▪ amebic antigens detection trophozoite cyst Prophylaxis of amebiasis  purification and control of water reservoirs  preservation of food products from houseflies  good personal hygiene  washing fruit and vegetables before consumption Entamoeba coli exists as a vegetative form in the large intestine, and is discarded outside with feces like cyst. Differences between Entamoeba coli and Entamoeba histolytica: E. histolytica E.coli Extranuclear chromatin material is called chromatoid body. Karyosome is a deoxyribonucleic acid (DNA) situated peripherally or centrally within the nucleus. 1. E.coli is larger, but less mobile. 2. In the cytoplasm of E.coli there are no erythrocytes. 3. Mature E.coli cysts are larger and are 8nuclear. 4. E.coli is a commensal in the colon and does not cause disease, unlike E. histolytica. REFERENCES: Created by: Assist. Prof. Dr. Stoyan Stoyanov