Establishing bacterial infectivity models in striped Catfish <i>Pangasianodon hypophthalmus</i> (Sauvage) with <i>Edwardsiella ictaluri</i>
Nguyễn Ngọc Phước, Randolph H. Richards, Margaret Crumlish
Abstract
Abstract A bacterial infectivity challenge model of Edwardsiella ictaluri in striped catfish was developed. All experiments were conducted using a bacterial isolate of E. ictaluri that had been recovered during a natural outbreak of bacillary necrosis of Pangasianodon (BNP) in farmed striped catfish Pangasianodon hypophthalmus in Vietnam. Time of immersion in 10 7 CFU.ml −1 had a significant effect on mortality. The immersion bacterial dose of 10 7 CFU/ml for 30 s resulted in a cumulative percentage mortality of 63%. Three to four days post‐bacterial challenge, fish showed gross clinical signs of natural BNP and E. ictaluri was recovered and identified from these fish. Moreover, a cohabitation challenge was evaluated as an alternative challenge method, although the mortalities among the infected fish were lower at around 15%–40%. This study confirmed the horizontal transmission of E. ictaluri in striped catfish and elucidated that cohabitation challenge could be used in reproducing the disease under controlled conditions.