Abstract
Our previous suggestion that the gill was a key organ for the development of pseudotuberculosis at the early phase of infection was evaluated in natural infection. From naturally infected amberjack Seriola dumerili groups at two fish farms, total 15 dead fish and total 18 apparently healthy fish were collected. In the dead fish, bacterial isolation rate from the kidney and the detection rates of the pathogen in the gills, kidney and spleen by fluorescent antibody method were 87, 100, 100 and 100%, respectively. In the apparently healthy fish, those rates were 6, 72, 33 and 33%, respectively. The quite high detection rate of the bacteria at the gills of the apparently healthy fish may confirm the suggestion.
