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T oxoplasmosis

T oxoplasmosis. Learning outcomes. By the end of the lecture, you should be able to: 1- Mention Causal Agent of Toxoplasmosis. 2- Mention systematic position of Toxoplasma gondii. 3- Mention geographic distribution of Toxoplasmosis.

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T oxoplasmosis

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  1. Toxoplasmosis

  2. Learning outcomes • By the end of the lecture, you should be able to: 1- Mention Causal Agent of Toxoplasmosis. 2- Mention systematic position of Toxoplasma gondii. 3- Mention geographic distribution of Toxoplasmosis. 4- Mention Intermediate and definitive hosts of Toxoplasma gondii. 5- Describe Forms and morphology of Toxoplasma gondii. 6- Mention habitat of different forms of Toxoplasma gondii. 7- Explain life cycle of Toxoplasma gondii. 8- Mention routes of disease Transmission. 9- Mention pathology and clinical features of Toxoplasmosis. 10- Diagnose Toxoplasmosis.

  3. Suggested Reading • http://www.dpd.cdc.gov/dpdx/HTML/Toxoplasmosis.htm • Chiodini, P.L.; Moody, A.H. and Manser, D.W. (2001): Atlas of Medical Helminthology and Protozoology. 4th ed. Churchill Livingstone, P. 59-60.

  4. Causal Agent of Toxoplasmosis • Toxoplasmosis is caused by Toxoplasma gondii. • Toxoplasma gondii is a protozoan parasite that infects most species of warm blooded animals, including humans, causing the disease toxoplasmosis.

  5. Systematic position of T. gondii • Phylum: Apicomplexa (Sporozoa). • Class: Coccidea. • Genus: Toxoplasma (T.) e.g. Toxoplasma gondii

  6. Geographic distribution of Toxoplasmosis • Toxoplasmosis is one of the most common of humans infections throughout the world. • Infection is more common in warm climates and at lower altitudes than in cold climates and mountainous regions. 

  7. Hosts of Toxoplasma gondii • Definitive host: • Cats. • Intermediate hosts: • Human. • Cattle. • Sheep. • Camel. • Pig. • Dogs. • Rodents. • Chickens

  8. Forms of T. gondii • Tachyzoite(acute stage, free or in pseudocyst in brain, liver, lung, spleen, bone marrow, eye, etc.) • Bradyzoite(chronic stage, in True cyst in different organs)

  9. Morphology Stages of the asexual cycle (in intermediate Host) • A- Trophozoite : - proliferative form , 6x3 µ - crescent in shape with one end pointed & the other rounded - has a nucleus.

  10. B- Pseudocyst • A host cell containing rapidly multiplying tachyzoites. • No cyst wall. • In acute infection.

  11. C-True Cyst • Dormant stage. • Contains bradyzoites • Surrounded by a cyst wall • 50-100µ • In chronic infection

  12. Stages derived from cat (D.H) • Sporulated oocyst: • Oval,10x12µ, transluscent • Di-sporocystic tetrazoic • Unsporulated oocyst: • Shed in faecs of cat, contains one sporoplast

  13. Different forms of T. gondii

  14. Life cycle of T. gondii • I- Sexual enteric cycle in cat: • Cats can acquire infection by ingestion of cysts (when they eat an intermediate host as rat), or mature oocysts in food and drinks contaminated with faeces of infected cats  release of trophozoites or sporozoites in the intestine  penetrate the enterocytes  multiple schizogony cycles. Then development of gametes occurs fertilization  zygotes  immature oocysts  external environment with faeces  mature within 3-4 days and become disporocystic tetrazoic oocysts. Moreover, asexual exoenteric multiplication may occur in tissues of the cat i.e. cat is a complete host

  15. Life cycle…..cont • Asexual exoenteric cycle in Intermediate host (as human): Ingestion of the infective stage(oocyst, cyst, or pseudocysts)  release of organisms (sporozoites or trophozoites) in the small intestine  penetrate the small intestinal wall, multiply in lymphoid macrophages in the lamina propria and then via lymphatics they reach the mesenteric lymph nodes where they proliferate  haematogenous spread to various organs pseudocysts in acute infection. In chronic infection, cysts are formed due to the developed host immunity. Then the intermediate host is infective if eaten by cats. • Human is a blind intermediate host.

  16. Life Cycle of T. gondii

  17. Unsporulated oocysts passed in faeces Infected fetus

  18. Routes of disease Transmission • Human and other animals infection may be acquired in several ways: 1- Ingestion of undercooked infected meat containing Toxoplasma cysts (true or pseudo-cyst) 2- Ingestion of the sporulated oocyst from fecally contaminated hands or food. 3- Organ transplantation or blood transfusion. 4- Transplacental (congenital) transmission. 5- Accidental inoculation of tachyzoites. 

  19. Clinical Features • Infection with Toxoplasma in immuno-competent persons is generally an asymptomatic infection. • However, 10% to 20% of patients with acute infection may develop: • A flu-like illness. • Cervical lymphadenopathy. • Atypical pneumonia. • Acute encephalitis. • Chorioretinitis. • Symptoms usually resolve within a few months to a year. 

  20. Clinical Features…cont. • In immunodeficient patients or infants (congenital) infection lead to: 1- Toxoplasmic encephalitis (hydrocephalus)

  21. Clinical Features ….…cont. 2- Myocarditis. 3- Retinochoroiditis(Ocular Toxoplasma infection)

  22. Laboratory Diagnosis of Toxoplasmosis 1-The detection of Toxoplasma-specific antibodies (IgM & IgG) is the primary diagnostic method to determine infection with Toxoplasma. 2- Observation of parasites in patient specimens, such as bronchoalveolar lavage or lymph node biopsy. 3- Isolation of parasites from blood or other body fluids, and intraperitoneal inoculation into mice or tissue culture.  4- Detection of parasite genetic material by PCR.

  23. Laboratory Diagnosis of Toxoplasmosis • Microscopy Findings T. gondii cyst in brain tissue stained with hematoxylin and eosin T. gondii tachyzoites

  24. Thank You

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