Experimental Infection of Indigenous Climbing Perch <i>Anabas testudineus</i> with <i>Aeromonas hydrophila</i> Bacteria

Abstract

The present study was conducted to know the pathogenicity and LD₅₀ of Aeromonas hydrophila isolated from diseased climbing perch Anabas testudineus against apparently healthy homologous fish and the distribution of the bacteria in the organs of the experimentally infected fish. A total of 10 fish of average body weight of 18 g were used. For pathogenicity test, two different doses viz. 9.2 × 10⁷ and 9.2 × 10⁶ CFU/fish were injected intramuscularly. Pathogenicity of A. hydrophila was confirmed at water temperature of 28.53^oC by the mortality of 40% to 100% of all tested fish within 4 to 9 days. The highest bacterial load was found to be 9.4 × 10⁸ CFU/g in the intestine and the lowest bacterial load was found to be 2.8 × 10³ CFU/g in the kidney of the tested fish. Four different serial concentrations, vide 9.2 × 10⁷, 9.2 × 10⁶, 9.2 × 10⁵ and 9.2 × 10⁴ CFU/fish of the bacteria were injected in each of four different groups of 10 fish. The calculated LD₅₀ value at 27.3^oC water temperature was 2 × 10⁷ CFU/fish of 18 g of average body weight. In all the cases of intramuscular injection, external pathology was found. Reddish anal region and fin bases were observed. Injected A. hydrophila was re-isolated from liver, kidney and intestine of the challenged fish. It was understood that the isolate was a high virulent pathogen for A. testudineus.

DOI: http://dx.doi.org/10.3329/pa.v22i1-2.16472

Progress. Agric. 22(1 & 2): 105-114, 2011