work (6), suggests that different fish pathogenic bacteria have
different sensitivities to herb extracts. For example, A. hydrophila
was more sensitive to P. guajava than A. paniculata (6), whereas S.
agalactiae was more sensitive to A. paniculata than P. guajava. Therefore,
to select an appropriate herb for controlling fish disease caused
by a specific bacterium, the sensitivity pattern of the bacterium to
various herb extracts needs to be confirmed.
An aqueous extract of A. paniculata was reported by Singha et al.
(14) to inhibit both Gram-positive and Gram-negative bacteria including
Bacillus cereus, Escherichia coli, and Pseudomonas aeruginosa.
They also mentioned that antimicrobial activity of aqueous extract of A.
paniculata may be due to the combined effect of arabinogalactan proteins
and andrographolides. Although the use of A. paniculata to control
diseases in fish has not been previously reported, the results from this
study and reports on its effective medicinal application in human,
encouraged in vivo trials of this herb in fish infected with S. agalactiae.
In this study, brief in vivo experiments were conducted by supplementing
commercial fish feed with dry leaf powder of A. paniculata or
dried matter of A. paniculata aqueous extract. The supplemented feeds
reduced the mortality rate of fish experimentally infected with S.
agalactiae and had no apparent adverse effect on the fish. Furthermore,
feeds supplemented with dried matter of A. paniculata aqueous
extract at ratios (w/w) of 4:36 and 5:35 resulted in an absence of
mortality in bacterial infected fish; identical to the results obtained
from groups treated with oxytetracycline. The results suggest that
there is a significant therapeutic potential in A. paniculata extracts,
and that they could be used to replace antibiotics to control
streptococcosis disease in Nile tilapia. Furthermore, in vivo experiments
on the use of A. paniculata supplemented fish feeds against
natural S. agalactiae infections in a Nile tilapia farm are underway