Characterization of bacterial pathogens of Litopenaeus vannamei (Boone) and their management through herbal extracts
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Date
2022-07
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Chaudhary Charan Singh Haryana Agricultural University
Abstract
The enterprise and personal profile of shrimp farmers of Punjab and Rajasthan showed that 50-60% operated their farms on lease basis, 60% were registered with Costal Aquaculture Authority, 90 % used their own money,70-80 percent used solar power in addition to generators. Forty percent of shrimp farmers in Punjab and 60 percent in Rajasthan were having farm area of 6 to 10 acres (2-4 ha). 40-60 % maintained high stocking density (> 1.5 lacks/acre), took two crops per year and received 300-350 Rs/Kg for shrimps with an income of 2-4 lacks/acre/season. In Rajasthan, 40 percent of shrimp farmers were educated to the graduate level, followed by higher secondary education (30%), while in Punjab, 40 percent were educated to the secondary level. Males dominated (90%) the shrimp farming sector, majority of shrimp farmers were between the ages of 30 and 40, closely followed by 20-40 years and had less than 5 years of experience. The yield was positively correlated with the stocking density (r=0.46) and negatively correlated with shrimp sampling (r= -0.48). White muscle, vibriosis, loose shell, black gill, white faecal matter, AHPND, EHP and IHHN were the most common diseases reported in surveyed farms. Significant positive correlation coefficient of percentage infection in shrimp pond water with salinity, TDS, Na, Cl, K, Mg, TSS, total hardness, EC, turbidity, Calcium hardness was recorded. Thirty two bacterial isolates were isolated from diseased shrimps having symptoms like white gut, transparent or pale body, red telson with lesions. The isolates were found to be from Vibrio, Shewanella, Staphylococcus, Pasturella, Escherichia and Klebsiella genus. The present study reported the first report of Shewanella khirikhana, a shrimp pathogen in India. Fourteen isolates (Vibrio sp.) of the present study are potential new species of Vibrio whose only taxon (LCUE_s) is identified. Vibrio spp., S. alage, S. khirikhana and combination of Vibrio and Shewanella isolates, at 104, 105, 106 CFU/ml caused mortality and decreased the growth parameters of Litopenaeus vannamei. The MIC of Curcuma longa, Tinospora cordifolia, Coriander sativumwas10, 15, 25 mg/ml against S. algae and 15, 20, 25 mg/ml against Vibrio sp. C. longa was most effective against the bacterial challenged shrimps followed by T. cordifolia and C. sativum. The mean length, weight, SGR, biomass, total protein, carbohydrate, lipids, total haemocyte count were significantly higher in shrimps treated with different herbal extracts than bacterial challenged shrimps. The concentration of antioxidative enzymes, catalase, superoxide dismutase and glutathione peroxidase were higher in Vibrio sp. and S. algae challenged shrimps. The enzymes were high in haepatopancreas followed by muscle, haemolymph. The potential probiotic strains, Bacillus subtilis BAA3 and B. subtilis BAA96 showed antimicrobial properties against Vibrio sp. and S. algae. B. subtilis BAA3 was more effective as probiotics than B. subtilis BAA96. The shrimps treated with B. subtilis strains exhibited higher survival, better growth parameters than bacterial challenged shrimps. Histopathological studies showed necrotic hepatic tubules, ruptured basement membrane, loss of normal B, R and F cells in bacterial challenged shrimps. BOD and pH of probiotics treated shrimp water was lower on termination of experiment than on 0 day.