An experimental model for Naegleria fowleri-induced primary amebic meningoencephalitis in rabbits.

A new model was developed in rabbits for primary amebic meningoencephalitis, a rare disease caused by the free-living ameba, Naegleria fowleri. Naegleria fowleri was cultured in a liquid axenic medium, and then injected intracisternally into New Zealand White rabbits. Inocula of 10(3) or 10(5) trophozoites consistently produced a sanguinopurulent meningitis; duration of survival of rabbits was 57 or 45 hr, respectively. Counts of cells in cerebrospinal fluid were proportional to the size of inoculum used; white blood cell counts ranged from 30 to 1,055 cells/mm3, and red blood cell counts from five to 8,640 cells/mm3. Necropsies revealed severe basilar meningoencephalitis with extensive hemorrhagic necrosis and polymorphonuclear cell infiltration. Trophozoites of N. fowleri were seen within the meningeal exudate and the brain parenchyma. Potential applications of this model include studies of the host response to amebae in the CSF, evaluation of the optimal route of administration of amphotericin B, and in vivo studies of other chemotherapeutic agents that show in vitro efficacy.