Therapeutic, histopathological, and non-specific immune status effect of Rhizophora mangle and Laguncularia racemose hydroalcoholic extracts against Vibrio harveyi and Vibrio campbellii in white shrimp (Penaeus vannamei)

The objective of the research was to evaluate in vitro and in vivo antibacterial efficacy of Rhizophora mangle and Laguncularia racemose when added to the feed of Penaeus vannamei in an experimental infection with Vibrio harveyi (CAIM 1792) and V. campbellii (CAIM 333). Results show that the minimum inhibitory concentration for both extracts was 1.65 g mL-1, with an inhibition zone of 25 ± 1 mm (V. campbellii); 18 ± 2 mm (V. harveyi) for L. racemose and of 21 ± 2 mm (V. campbellii); 20 ± 2 mm (V. harveyi) for R. mangle. R. mangle gave a higher total content of phenolic compounds (4.50 ± 0.26 mg GAE mL-1) and flavonoids (2.60 ± 0.15 mg QE mL-1). The challenge with V. harveyi resulted in 70% survival for organisms fed L. racemose extract and 53% for R. mangle extract. The challenge with V. campbellii resulted in 80% survival for organisms fed L. racemose and 90% R. mangle. Histopathological alterations were observed in the hepatopancreas with hemocytic infiltration within the intertubular connective tissue. Also, tubules with severe cell detachment and tubular atrophy were detected in the positive control organisms, and organisms treated with R. mangle and L. racemose only had vermiform structures in the tubular lumen, cell detachment, and infiltration hemolymph in intertubular connective tissue. According to the analysis of the studied variables, it can be concluded that the hydroalcoholic extracts of R. mangle and L. racemose reduced mortality, clinical signs, and organs and tissue alterations and improved P. vannamei immunity. It is possible to use these hydroalcoholic therapeutic extracts as treatments in shrimp-farm to enhance bacterial disease tolerance and prevent mortality.