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Toxoplasma gondii in the peripheral blood of patients with acute and chronic toxoplasmosis
  1. Cláudio Silveira1,
  2. Adriana Lima Vallochi2,
  3. Ulisses Rodrigues da Silva2,
  4. Cristina Muccioli1,
  5. Gary N Holland3,
  6. Robert B Nussenblatt4,
  7. Rubens Belfort1,
  8. Luiz Vicente Rizzo2,5,6,7
  1. 1Department of Ophthalmology, Escola Paulista de Medicina—Federal University of São Paulo, São Paulo, Brazil
  2. 2Department of Immunology, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil
  3. 3Ocular Inflammatory Disease Center, Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
  4. 4Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA
  5. 5Albert Einstein Jewish Institute for Education and Research, São Paulo, Brazil
  6. 6Institute for Investigation in Immunology, Brazilian Ministry of Science and Technology, São Paulo, Brazil
  7. 7Hospital Israelita Albert Einstein, São Paulo, Brazil
  1. Correspondence to Professor Luiz Vicente Rizzo, Hospital Israelita Albert Einstein, Av Albert Einstein 627/701, Chinuch Level, Josef Feher Building, São Paulo, SP - Brazil, CEP 05652-000; lvrizzo{at}


Background and aims Toxoplasmic retinochoroiditis may recur months or years after the primary infection. Rupture of dormant cysts in the retina is the accepted hypothesis to explain recurrence. Here, the authors present evidence supporting the presence of Toxoplasma gondii in the peripheral blood of immunocompetent patients.

Methods Direct observation by light microscopy and by immunofluorescence assay was performed, and results were confirmed by PCR amplification of parasite DNA.

Results The authors studied 20 patients from Erechim, Brazil, including acute infected patients, patients with recurrent active toxoplasmic retinochoroiditis, patients with old toxoplasmic retinal scars, and patients with circulating IgG antibodies against T gondii and absence of ocular lesions. Blood samples were analysed, and T gondii was found in the blood of acutely and chronically infected patients regardless of toxoplasmic retinochoroiditis.

Conclusions The results indicate that the parasite may circulate in the blood of immunocompetent individuals and that parasitaemia could be associated with the reactivation of the ocular disease.

  • Toxoplasma gondii
  • tachyzoites
  • parasitaemia
  • ocular toxoplasmosis
  • choroid
  • retina
  • renitochoroiditis

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  • CS, ALV, RB and LVR contributed equally.

  • Funding This study was supported by Fundação de Amparo a Pesquisa de São Paulo and Conselho Nacional de desenvolvimento Científico e Tecnológico.

  • Competing interests None.

  • Ethics approval Ethics approval was provided by the São Paulo University, Biomedical Sciences Institute and Federal University of São Paulo, Department of Ophthalmology.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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