Cyst Rupture as a Pathogenic Mechanism of Toxoplasmic Encephalitis

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  • University of Kansas Medical Center, Gorgas Memorial Laboratory, Kansas City, Kansas 66103, Republic of Panama
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Seemingly intact cysts and sequential stages of disintegrating cysts of Toxoplasma were identified immunohistologically within developing microglial nodules in a Panamanian night monkey (Aotus lemurinus). This monkey had been successfully immunized and challenged 5 months earlier. This supports the hypothesis that glial nodules unassociated with Toxoplasma tachyzoites may represent the tombstone of a Toxoplasma cyst. Disintegration of cysts may give rise to clinical encephalitis in the presence of apparently adequate immunity.