This study reinforces the view that garlic is beneficial for the
control of A. hydrophila infection in rainbow trout, and thereby
extends the previous study [10], by demonstrating the long-term
memory effect after the cessation of the feeding regime. Of relevance
to the present study, a previous investigation using brook
trout, Salvelinus fontinalis, which were administered with chitosan
by a 30-min immersion led to reduced protection 14 days afterwards
[23]. Moreover by 21 days after concluding the administration
of chitosan, there were not any significant differences in the
levels of protection with the controls. Certainly, it has been argued
that the long-term application of immuno-stimulants leads to
immuno-suppression and loss of effect of the compounds [24,5].
Indeed, it is speculative whether or not a similar effect could have
happened in this study.