Effects of a Myrrh (Commiphora myrrha) Essential Oil Supplemented Diet on Haemato-Biochemical Parameters, Expression of Tissue-Specific Immune- and Stress-Related Genes, and Resistance of Cyprinus carpio to Aeromonas hydrophila Infection

Plant-based additives or botanicals, have garnered considerable interest in the aquaculture industry for their multifaceted benefits in fish diets. In this study, a 30 days short term feeding experiment was designed to determine the effects of Myrrh (Commiphora myrrha) essential oil on hematological, biochemical parameters and tissue specific mRNA expression responses of common carp (Cyprinus carpio). Fish were experimentally infected with Aeromonas hydrophila and monitored for 20 days after been divided in four groups: a control group without C. myrrha and three experimental groups supplemented with 0.25%, 0.50%, and 1.0% C. myrrha essential oil (CMO 0.25, CMO 0.50, and CMO 1.0, respectively). Results revealed a significant increase in RBC count, hemoglobin, and hematocrit values compared to the control diet. Positive effects of C. myrra supplementation have been observed also in serum biochemistry parameters. mRNA transcripts of il-1 ss, tnf-alpha, il-8, sod, cat, gpx and gst genes significantly increased in spleen and liver tissue of fish fed with C. myrra supplemented diets. After the challenge with Aeromonas hydrophila, the survival rates were 60%, and 83.33%, respectively, suggesting enhanced fish resistance in the CMO 0.50 and CMO 1.0 groups compared to the control. The results suggest the immunomodulatory roles of C. myrrha essential oil.