Evaluation of pathogenicity of motile Aeromonasrnspecies in African catfish

Abstract

This study was conducted to evaluate the ability of motile Aeromonas species (MAS) to induce skinrnlesions and cause mortality in African catfish (ACF). Eight motile Aeromonas isolates (A. hydrophila – 4rnisolates, A. caviae – 2 isolates and A. sobria – 2 isolates) were used for the study. Ninety apparentlyhealthyrnACF juveniles were randomly assigned into 9 groups of 10 fish each. Fish in groups 1 – 4 wererninfected with A. hydrophila while those in groups 5 – 6 and 7 – 8 were infected with A. caviae and A.rnsobria, respectively. Infection was achieved by immersing fish in water containing 1x108 colony formingrnunits (cfu)/ml of experimental isolate. Fish in group 9 were immersed in water containing sterilernphosphate buffered saline (PBS) and served as the control. Fish in the infected and control groups werernmonitored daily for 15 days for signs of ill health including development of skin lesions and mortality.rnSkin lesions were processed for re-isolation of MAS. Skin lesions were found in 40 – 90% ofrnexperimentally-infected fish while none of the uninfected had skin lesion. Mortality rate in infected fishrnranged from 20 – 90% while none of the uninfected died. Development of skin lesions as well asrnmortality in the ACF was associated with experimental infection with Aeromonas isolates. This study hasrnshown that MAS could serve as the primary cause of skin lesions in cultured ACF.