Identification and analysis of pathogenic bacteria causing outbreaks in Indian major carp aquaculture of Tripura.

OBJECTIVE: The objective of this study was to investigate bacterial disease outbreaks in Indian major carp from aquaculture systems in Tripura, India, and identify the bacterial species associated with those outbreaks. METHODS: A 3-year surveillance was conducted in eight districts of Tripura, during which nine bacterial disease outbreaks were recorded. Fourteen bacterial strains isolated from diseased Indian major carp were selected and identified using phenotypic, molecular (16S ribosomal RNA gene), and phylogenetic analyses. In vitro pathogenicity studies were performed to assess the potential pathogenicity of the isolated bacteria. RESULT: The selected isolated strains were preliminarily identified under the genera Aeromonas (9 isolates), Acinetobacter (1 isolate), Citrobacter (3 isolates), and Pseudomonas (1 isolate). Molecular and phylogenetic analyses confirmed the species of the isolated bacteria, including Aeromonas jandaei (strains COF_AHE09 and COF_AHE61), Aeromonas veronii (strains COF_AHE13, COF_AHE52, COF_AHE55, COF_AHE56, and COF_AHE62), Aeromonas hydrophila (strains COF_AHE51 and COF_AHE58), Acinetobacter pittii (strain COF_AHE14), Citrobacter freundii (strains COF_AHE20, COF_AHE57, and COF_AHE59), and Pseudomonas aeruginosa (strain COF_AHE54). Behavioral and clinical signs observed in the diseased fish, such as lethargy, skin hemorrhaging, ulcers, fin and tail rot, exophthalmia, distended abdomen, scale loss, and skin discoloration, indicated the presence of bacterial septicemia. The in vitro pathogenicity studies highlighted the potential role of these bacteria in disease development, especially under environmental stress. CONCLUSION: This study provides valuable insights into the diversity of bacterial species associated with bacterial disease outbreaks in Indian major carp from aquaculture systems in Tripura. It serves as the first comprehensive investigation of its kind, contributing to our understanding of bacterial infections in Indian major carp.

Ameliorating effects of dietary mixture of Withania somnifera root extract and vitamin C in Labeo rohita against low pH and waterborne iron stresses.

The present study was conducted to elucidate the possible effect of a combination of Withania somnifera (Ashwagandha) root extract and dietary l-ascorbic acid (vitamin C) on the immune responses and survivability in Labeo rohita fingerlings against low pH and waterborne iron toxicity. Four diets were prepared containing 0% (control), 0.01% (T1), 0.1% (T2) and 1.0% (T3) of a combination of Withania somnifera (Ashwagandha) root extract and dietary l-ascorbic acid (vitamin C) at the rate of 1:1 (w/w). Fishes were fed for 60 days to find out the best dose and duration of feeding by examining different haematological (haemoglobin, haematocrit, total RBC count, total WBC count, MCV, MCH and MCHC), immunological (NBT, lysozyme and total immunoglobulin activity) and biochemical (glucose, total protein, ALP, SGPT and SGOT level) parameters on 7, 15, 30 and 60 days of feeding. The best response was observed in fish fed with diet T3 within 15 days. The result showed a significant (p < 0.05) increase in haemoglobin, haematocrit, total RBC count, total WBC count, NBT, lysozyme activity, total immunoglobulin and total protein whereas a significant (p < 0.05) decrease in glucose, ALP, SGPT and SGOT level compared to control. Challenged study against waterborne iron (6.02 mg l-1) and low pH (4.2-4.5) after feeding the fish for 15 days with diet T3 showed significantly (P < 0.05) higher protection than control. The study concludes that inclusion of 1.0% Withania somnifera (Ashwagandha) root extract and dietary l-ascorbic acid (vitamin C) combination in diet have a stimulatory effect on immune response and reduces the effect of multiple stresses (i.e., low pH and waterborne iron toxicity) in L. rohita fingerlings.