Received: 05-01-2021 / Accepted: 23-04-2021
The study was conducted to compare and evaluate the cross-infection possibility of Edwardsiella ictaluricausing diseases in tilapia and Channel catfish. The strains ofE. ictaluriisolated from tilapia and Channel catfish were compared based on the biochemical characteristics, PCR confirmation, lethal doses and the possibility of cross-infection among other fish species. The results revealed that E. ictaluriisolated from tilapia and Channel catfish differed in 2/22 biochemical reactions (citrate utilization, Voges-proskauer) but they were identical in PCR assay. The virulence of E. ictaluristrains from tilapia was high when they were challenged to tilapia (LD50= 2.5 101CFU/fish) but remarkably decreased to Channel catfish (LD50= 2.0 106CFU/fish). Similarly, the isolates from Channel catfish exhibited a high virulence in this fish (LD50= 4.7 103CFU/fish) but reduced their pathogenicity to tilapia (LD50= 2.5 106CFU/fish). The primary result demonstrates that E. ictaluricausing diseases in Channel catfish and tilapia differed in several characteristics. However, they cause relatively high mortality of fish when cross-infection among fish species at high bacterial densities. Thus, biosafety is required to avoid the spreading of pathogens in the culture systems.