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

• Main Authors: A. A. Tafi, S. Meshkini, A. Tukmechi, M. Alishahi, F. Noori
• Format: Article
• Language: English
• Published: Razi Vaccine and Serum Research Institute 2020-06-01
• Series: Archives of Razi Institute
• Subjects: cineol; histopathology; medicinal herbs; oncorhynchus mykiss; streptococcus iniae
• Online Access: https://archrazi.areeo.ac.ir/article_121492_07e22eb97e24c6a95943542c0fc23b90.pdf

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 <em>Aloe vera</em> and <em>Salvia officinalis</em> hydroethanolic extracts against <em>Streptococcus iniae</em> in rainbow trout. Plant extracts components were analyzed by Gas chromatography-mass spectrometry method and tested <em>in vitro</em> against <em>S. iniae</em> by disk diffusion assay. In <em>in vivo</em>, 480 rainbow trout (10±0.1 g) were distributed in 9 groups (with 3 replication), and all groups (except for the first group as the negative control that was injected with 100 µl of physiologic serum) were injected by 100 µl of LD₅₀ (3.66×10^8.5CFU/ml) of <em>S. iniae</em> suspension, intraperitoneally. The fish of groups were treated by <em>A. vera</em> and <em>S. officinalis</em> extracts in doses 0 (positive control group was fed by commercial diet without plant extract), 0.5, 1, and 1.5% (supplemented diet) and 80 mg/kg body weight erythromycin for the next 10 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 <em>A. vera</em> and <em>S. officinalis</em> had antibacterial components as Cineol, and <em>S. iniae</em> was sensitive to both <em>A. vera</em> (MBC=4.067 mg/ml) and <em>S. officinalis</em> (MBC=5.185 mg/ml) extracts. At the end of the treatment period, there were no significant differences among erythromycin,<em> A. vera</em> (1.5%), and <em>A. vera</em> (1%) in terms of the mortality of the infected fish (P˂0.05). Moreover, <em>A. vera</em> (1.5%) showed a significantly lower mortality rate, compared to the positive control (P˂0.05).<em> A. vera</em> (1.5%) was the best group to moderate all histopathological lesions, compared to other groups. Accordingly, <em>A. vera</em> (1.5 %) is useful to treat <em>streptococcosis</em> (caused by <em>S. iniae</em>) and alter gill and liver histopathological lesions in rainbow trout.