Epidemiology of edwardsiella infections in farmed fish in Morogoro, Tanzania

M.Sc. Dissertation

cross sectional study was undertaken from November 2016 to April 2017 to find out whether Edwardsiella infections exist in farmed fish in Morogoro. The prevalence of infection, risk factors and fish haematological parameters were established. A total of 270 fish were sampled from 24 ponds. Each fish was clinically examined and aseptically swabs of kidney, liver and spleen and pond water were collected for bacteriology. Bacteria were cultured onto Tryptic soya agar and Salmonella-Shigella Agar. Colony morphology and biochemical tests were used for phenotypic identification of the bacterium and confirmed by conventional PCR through detection of gyrB, IRS and IVS in the 23S rRNA gene for E. tarda and E. ictaluri, respectively. Presumptive results identified 14 Gram-negative, rod-shaped similar biochemically with Edwardsiella bacterial isolates. Out of 14 only four isolates amplified the gyrB gene using specific E. tarda primers. Overall, the prevalence of E. tarda in the study area was 1.48% (n=270). Clarias gariepinus was at a higher risk of acquiring E.tarda infection than Oreochromis niloticus (P < 0.05). Since the bacterial prevalence was low, it was not possible to establish the correlation with hematological parameters. In addition, there was no association between water quality and the prevalence of E. tarda infections. For the first time, this study isolated and confirmed the occurrence of E. tarda pathogens in farmed fish in Morogoro, Tanzania. However, more work on virulence studies on E. tarda isolates need to be done. The establishment and implementation of biosecurity measures to prevent disease outbreak in fish farms is also recommended taking into account its zoonotic potential.

TRAHESA