Dose Titration Study of Florfenicol as a Therapeutic Agent in Naturally Occurring Pseudotuberculosis

Abstract

Three groups of young yellowtail naturally infected with Pasteurella piscicida were given florfenicol (FF) for 5 consecutive days at dosages of 0, 5, 10 or 30 mg/kg/day.
Cumulative mortality varied but daily changes in mortality were similar among the groups before reatment. These differences of mortality before treatment do not seem so larges as to affect mortality rates during the dosing period and the evaluation of the treatment.
Daily mortality decreased rapidly in the groups treated with 5, 10 and 30 mg/kg/day of FF, while it remained at a high level for a long time in the non-medicated group.
Cumulative mortality of the FF-medicated groups during the dosing period (2nd day of dosing to 3 days after the last dosing) were significantly lower than those of the non-medicated groups. Among the medicated groups, the mortality of the 5 mg/kg/day FF-medicated groups were consistently higher than those of the 10 or 30 mg/kg/day groups.
Cumulative mortality during the dosing period decreased with the increase of the FF dose. The mean cumulative mortalities were 23.1, 11.5, 8.3 and 6.7 % in the groups treated with 0, 5, 10 and 30 mg/kg/day of FF, respectively.
From these results, it is concluded that 10 mg/kg/day of FF for 5 days is sufficiently effective as treatment for naturally occurring pseudotuberculosis in yellowtail.