Isolation and experimental infection of free-living amebae in freshwater fishes.

Twenty-three species of fish from nine southeastern states were screened for the presence of small, free-living amebae. Organs from 11 species of fish contained amebae of the genera Acanthamoeba, Naegleria, and Vahlkampfia. Three strains of Acanthamoeba were injected into fish to determine infectivity and pathogenicity of the amebae. Strains used were an A. polyphaga MC-1 isolated from the spleen of a bass, the pathogenic A-5 strain of A. culbertsoni, and the pathogenic Lilly A-1 strain of A. culbertsoni. The MC-1 strain established systemic infections in many organs of the test fish. The 2 strains of A. culbertsoni did not produce any infection in fish under the laboratory conditions.