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Protist parasite of human importance

Protist parasite of human importance. Disease : Toxoplasmosis Agent : Toxoplasma gondii Diverse routes of transmission Tissue-inhabiting Apicomplexan. Zoonosis. At risk groups. Life cycle of Toxoplasma. Toxoplasma life cycle stages. Oocyst. Bradyzoites. Tachyzoites.

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Protist parasite of human importance

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  1. Protist parasite of human importance Disease : Toxoplasmosis Agent : Toxoplasma gondii Diverse routes of transmission Tissue-inhabiting Apicomplexan. Zoonosis. At risk groups.

  2. Life cycle of Toxoplasma

  3. Toxoplasma life cycle stages Oocyst Bradyzoites Tachyzoites

  4. Bradyzoites within tissue cysts

  5. Toxoplasma gondii : Modes of transmission • Ingestion of cyst-containing meat (carnivores) • Ingestion of oocysts (environmental contamination) • Congenital infection • Transfusion (rare) • Raw goat’s milk, lambing, transplantation

  6. Percentage of Toxoplasma infection associated with type of meat consumed Adapted from Sukthana, 2006

  7. Seropositivity rates

  8. Symptomatology : Toxoplasma • Most infections benign • Rarely severe • hepatitis, encephalomyelitis, myocarditis • Few cases of retinochoroiditis which can progress to blindness • At risk groups (see over)

  9. Intra-uterine infections • Severe clinical picture : retinochoroiditis, encephalomyelitis, hydrocephalus, microcephaly • Most infections result in blindness, severe visual impairment and/or mental retardation • Estimates 50-70 seriously affected births UK ; approx 3000 congenital cases USA

  10. Toxoplasma in the immunocompromised host • Immunosuppression, malignancy, AIDS, organ transplantation • Neurological complications - meningoencephalitis or cerebral mass lesions : cerebral toxoplasmosis • Headache, confusion, ataxia, hemiparesis, retinochoroiditis • Endogenous versus exogenous infection

  11. Cerebral toxoplasmosis : Centre for Disease Control (CDC) criteria for diagnosis • Recent onset of focal neurological abnormality consistent with intercranial disease or reduced consciousness • Evidence from brain imaging of a lesion (CT or MRI) • Positive serum antibody to T. gondii or response to treatment

  12. Diagnostic tests for Toxoplasma • Sabin-Feldman dye test (DT) • Enzyme immunoassay for T. gondii specific IgM (EIA) • Immunsorbent agglutination assay (ISAGA) • Enzyme immunoassay for IgG avidity • Isolation and culture of parasite • Direct detection by microscopy and PCR

  13. Differential Diagnosis • Immunocompetent adults (DT, IgM EIA) • Pregnant women (maternal serum DT, IgM EIA, IgG avidity; Amniotic fluid culture or PCR) • Neonates (DT, EIA, ISAGA for IgM, IgA) • Organ transplantation (DT, IgM EIA) • Immunodeficiency (serum and CSF : DT, EIA, ISAGA for IgM and IgA; PCR, culture, microscopy)

  14. Prevention and control • Avoid consumption of raw or undercooked meat • Litterpans should be changed daily • Wash hands after handling raw meat, litter pans & soil • Pregnant women should avoid contact with cats • Issue of prenatal screening

  15. Program for mass screening and prophylactic treatment of pregnant women for T. gondii

  16. Treatment : toxoplasmosis • Only accepted treatment pyrimethamine with trisulfapyrimines for 1 month • Intravenous clindamycin used to treat encephalitis in AIDS patients • In France spiramycin has been used to treat toxoplasmosis in pregnancy • Spiramycin is available in the US on a case-by-case basis

  17. Seroprevalence of Toxoplasmosis by county of maternal residence % Ferguson et. al. 2009 IMJ

  18. Toxoplasma and Schizophrenia Robert H. Yolken, F.B. Dickerson & E. Fuller Torrey (2009) Parasite Immunology 31 (11), 706-715

  19. Key points • Individuals with schizophrenia higher seroprevalence of Toxoplasma • Epidemiology of Toxoplasma and schizophrenia similar • Antipsychotic drugs inhibit Toxoplasma • Toxoplasma induces elevated levels of dopamine • Individuals with schizophrenia higher exposure to cats

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