Subacute and chronic meningoencephalitis in mice after experimental infection with a strain of Naegleria fowleri originally isolated from a patient.

Swiss mice were inoculated intranasally with trophozoites of a cloned substrain of the Naegleria fowleri strain LL originally isolated from a human being. The original strain had decreased in virulence after ten years of maintenance in axenic culture. survivors were sacrificed from the fourth to the tenth week p.i. They were tested in a labyrinth experiment in which some demonstrated a diminution in performance. N. fowleri could be reisolated from the brains of five clinically inconspicuous animals. The histopathological findings in the brains of these animals resembled the features of a chronic granulomatous amebic encephalitis (GAE) which has been described in infections due to Acanthamoeba spp. It was not expected that N. fowleri could also produce latent infections. The significance of these findings is discussed.