Therapeutic and Histopathological Effect of Aloe vera and Salvia officinalis Hydroethanolic Extracts against Streptococcus iniae in Rainbow Trout

Some of the medicinal plants have antibacterial contents and appear to be proper alternatives for antibiotics in the treatment of streptococcal disease, which causes plenty of mortalities in fish farms annually. Therefore, this study investigated the therapeutic effect of Aloe vera and Salvia officinalis hydroethanolic extracts against Streptococcus iniae in rainbow trout. Plant extracts components were analyzed by Gas chromatography-mass spectrometry method and tested in vitro against S. iniae by disk diffusion assay. In in vivo, ۴۸۰ rainbow trout (۱۰±۰.۱ g) were distributed in ۹ groups (with ۳ replication), and all groups (except for the first group as the negative control that was injected with ۱۰۰ µl of physiologic serum) were injected by ۱۰۰ µl of LD۵۰ (۳.۶۶×۱۰۸.۵CFU/ml) of S. iniae suspension, intraperitoneally. The fish of groups were treated by A. vera and S. officinalis extracts in doses ۰ (positive control group was fed by commercial diet without plant extract), ۰.۵, ۱, and ۱.۵% (supplemented diet) and ۸۰ mg/kg body weight erythromycin for the next ۱۰ days. At the end of the study period, tissue samples of the gills and livers of all groups were taken for the histopathological lesion assay. The results showed that A. vera and S. officinalis had antibacterial components as Cineol, and S. iniae was sensitive to both A. vera (MBC=۴.۰۶۷ mg/ml) and S. officinalis (MBC=۵.۱۸۵ mg/ml) extracts. At the end of the treatment period, there were no significant differences among erythromycin, A. vera (۱.۵%), and A. vera (۱%) in terms of the mortality of the infected fish (P˂۰.۰۵). Moreover, A. vera (۱.۵%) showed a significantly lower mortality rate, compared to the positive control (P˂۰.۰۵). A. vera (۱.۵%) was the best group to moderate all histopathological lesions, compared to other groups. Accordingly, A. vera (۱.۵ %) is useful to treat streptococcosis (caused by S. iniae) and alter gill and liver histopathological lesions in rainbow trout.

کلیدواژه ها:

Cineol ، Histopathology ، Medicinal herbs ، Oncorhynchus mykiss ، Streptococcus iniae