Pangasius catfish, Pangasius nasutus, is a promising candidate for aquaculture due to its high market value. However, the presence of pathogenic bacteria in Aeromonas hydrophila is a major concern in P. nasutus farming in this country. This study determines the pathogenicity of A. hydrophila in P. nasutus. A total of 80 P. nasutus juveniles were intraperitoneally injected with 0, 10³, 10⁵, and 10⁷ CFU mL^-1 of A. hydrophila and monitored until 240 hr. The infected moribund fish’s kidneys, livers, and spleens were collected for histopathological analysis. The LD_50-240hr value was found at 0.8 × 10⁴ CFU/ml of A. hydrophila. The percentage of mortality in 0, 103, 105, and 107 CFU/ml infected groups were found to be at 0, 40, 60, and 90%, respectively. The infected fish showed congestion at the base of the fin, ascites, enlarged gall bladder, and swollen spleen. It is the earliest report on A. hydrophila’s pathogenicity in high-value native fish, P. nasutus.

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