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Lab 9 -toxoplasmosis
- 5. Morphology 1. tachyzoites (trophozoites). 2. tissue cysts (bradyzoites). 3. oocyst. Oocyst Tachyzoites Bradyzoites Toxoplasma gondii exists in three forms:_
- 9. Intracellular in cell culture. Note a group arranged in a rosette (arrow) and vacuole (arrowhead) around a tachyzoite. 1.Tachyzoite
- 11. Tissue cysts Tissue cysts of Toxoplasma gondii filled with bradyzoites
- 12. Toxoplasmosis: brain cyst at low magnification
- 13. Toxoplasmosis: brain cyst at high magnification
- 16. G.D. Cosmopolitan Habitat:- Macrophage and most nucleated cells, toxoplasmosis favored host cells are the muscle and brain cells. Disease Toxoplasmosis Intermediate Host most mammals and most birds are susceptible to infection. Definitive Host Cat Toxoplasma gondii
- 18. Toxoplasma gondii Tissue phase (intermediate hosts). infected by ingesting sporulated oocysts. Intermediate host Human, cattle, birds, rodents, pigs, and sheep. 1 to 5 days 3-10
- 19. Toxoplasma gondii Cat’s intestinal enterocytes Bradyzoites infect cells and become tachyozoites. Tissue cyst Multiplication Merozoites Gametocytes Zygote Oocyst Encapsulation of zygote within a rigid wall: oocyst
- 21. Toxoplasma gondii Diagnosis 1- Microscopic examination * Tissue biopsy * CSF 2- Serological diagnosis * ELISA * IFAT * Latex agglutination Test
- 24. Next Lab Enteric Apicomplexa: Cryptosporidium parvum
Notas do Editor
- Having an immune system that has been impaired by disease or treatment. having the immune response attenuated by administration of immunosuppressive drugs, by irradiation, by malnutrition, or by certain disease processes (e.g., cancer). Medicine / Pathology) having an impaired immune system and therefore incapable of an effective immune response, usually as a result of disease, such as AIDS, that damages the immune system. Incapable of developing a normal immune response, usually as a result of disease, malnutrition, or immunosuppressive therapy.
- capable of developing an immune response following exposure to an antigen; "immunocompetent cells“ Having a functioning immune system. Able to develop an immune response. Able to recognize antigens and respond to them. The opposite of immunodeficient.
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- The size of young tissue cysts may be as small as 5 μm in diameter and contain only two bradyzoites while older ones varies between 50-150 µm and may reach 200 µm ,and it might contain about 3000 closely packed bradyzoites
- As host resistance develops, usually around 3 weeks post infection, tissue cysts may form in many organs, primarily in brain and muscle.
- In places where raw meat consumption is usual, population shows high prevalence of toxoplasmosis An important percentage of AIDS patients die because of toxoplasmosis Cattle is less prone to Toxoplasma infection than is sheep (or pigs). - Toxoplasma -induced abortion is frequent in sheep/goats, bur it is much less frequent in cattle. Usually cold and dry climates are unfavourable for toxoplasmosis (oocysts are killed by low temperatures and sun exposure). Tropical or moist climates favours Toxoplasma survival Members of the cat family (Felidae) are the only known definitive hosts for the sexual stages of T. gondii and thus are the main reservoirs of infection.
- - In acute infection phase, infected hens can transmit the Protozoa to their eggs.
- Tachyzoites are the motile, asexually reproducing form of the parasite. Unlike the bradyzoites, the free tachyzoites are usually efficiently cleared by the host's immune response, although some manage to infect cells and form bradyzoites, thus maintaining the infection. Tissue cysts are ingested by a cat by feeding on an infected mouse. The cysts survive passage through the stomach of the cat and the parasites infect epithelial cells of the small intestine where they undergo sexual reproduction and oocyst formation. Oocysts are then shed with the feces. Animals and humans that ingest oocysts by eating unwashed vegetables or tissue cysts in improperly cooked meat become infected. The parasite enters macrophages in the intestinal lining and is distributed via the blood stream throughout the body. Members of the cat family (Felidae) are the only known definitive hosts for the sexual stages of T. gondii and thus are the main reservoirs of infection. Cats become infected with T. gondii by eating infected tissue of prey. After tissue cysts or oocysts are ingested by the cat, viable organisms are released and invade epithelial cells of the small intestine where they undergo an asexual followed by a sexual cycle and then form oocysts, which are excreted. The unsporulated oocyst takes 1 to 5 days after excretion to become infective. Although cats shed oocysts for only 1 to 2 weeks, large numbers may be shed. Oocysts can survive in the environment for several months and are remarkably resistant to disinfectants, freezing, and drying, but are killed by heating to 70°C for 10 minutes.
- (gametogony, the production of gametes)
- Diagnosis of toxoplasmosis can be aided by serologic or histocytologic examination. Clinical signs of toxoplasmosis are nonspecific and cannot be depended on for a definite diagnosis; toxoplasmosis clinically mimics several other infectious diseases. Many serologic tests have been used to detect antibodies to T gondii. The most reliable of these is the Sabin-Feldman dye test. Live virulent tachyzoites of T gondii are used as antigen and are exposed to dilutions of the test serum and to a complement accessory factor resembling complement that is obtained from Toxoplasma-antibody free-human serum. This test is sensitive and so far is the most specific test for toxoplasmosis. Its main disadvantages are its high cost and the human hazard of using live organisms. The indirect fluorescent antibody test (IFAT) overcomes some of the disadvantages of the dye test. In IFAT, killed tachyzoites of Toxoplasma, which are available commercially, are used as antigen. Titers obtained by IFAT are similar to those from the dye test. Disadvantages of the IFAT are that a microscope with UV light is needed, fluorescent anti-species globulin is required for each species to be tested, and false-positive titers may occur in hosts with anti-nuclear antibodies. The suitability of IFAT in animal diagnostic work is therefore limited, but it has proved useful in diagnosing acquired human toxoplasmosis. Other serologic tests including the indirect hemagglutination test, the latex agglutination test, modified agglutination test, and the enzyme-linked immunoabsorbent assay (ELISA), offer some advantages. For example, agglutination tests are easy to perform.
- Most asymptomatic (80-90%) Other 10-20% have Painful swollen lymph node, Fever, headache, and muscle pain
- Most asymptomatic (80-90%) Other 10-20% have Painful swollen lymph node, Fever, headache, and muscle pain