Atypical Aeromonas salmonicida Infection in Sailfin Sandfish Arctoscopus japonicus

In 2009, a disease with cumulative mortality of 52.5% was observed in a captive population of sailfin sandfish Arctoscopus japonicus reared at an aquarium in Japan. The affected fish had no apparent lesions on the body surfaces, with the exception of skin abrasions on the lower jaw. The trunk kidney was swollen and bore white miliary nodules. The most prominent histopathological feature of the diseased fish was numerous bacterial colonies in the internal organs. However, no inflammatory cellular response was apparent. Single species of bacteria was isolated from the trunk kidney and spleen, and identified as atypical A. salmonicida based on the biochemical and serological characteristics.