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Penaeus vannamei farming has been the major aquaculture practice in the Indian Sundarbans. This study investigated the physicochemical characteristics, management practices, distribution of vibrios, and the prevalence of bacterial, parasitic and viral diseases in 14 P. vannamei intensive culture farms in the Indian Sunderbans during 2016. The total heterotrophic counts of the pond water ranged from 3.53 to 6.21 log10 cfu/ml. The presumptive vibrios were in the range of 2.40-4.99log10 cfu/ml. Mild vibriosis was noted in 3 farms. Twenty out of 21 isolates from the haemolymph samples were confirmed to be Vibrio parahaemolyticus by the PCR amplification of toxR gene. No acute hepatopancreatic necrosis disease (AHPND) causing V. parahaemolyticus (Vp AHPND) strain was, however, detected. Of the 14 shrimp farms surveyed, only one farm sample was white spot virus (WSV) positive and all others were negative. All the P. vannamei farms were negative for infectious hypodermal and haematopoietic necrosis virus, hepatopancreatic parvo-like virus, and infectious myonecrosis virus. No incidence of Enterocytozoon hepatopenaei, white faecal syndrome, running mortality syndrome, protozoan infestation, and luminous vibriosis was observed during the survey period. The survival rate was 90-95% in the normal ponds, while the lowest survival was 60% in an asymptomatic WSV infected farm. The physicochemical characteristics of the farms were well within the optimum, except the WSV infected farm, which had high ammonia levels. Due to the lack of awareness on the P. vannamei farming practices and high operational costs, the biosecurity measures were not strictly followed in the surveyed farms.

Immunomodulation is one of the useful tools to prevent diseases in aquaculture. In this study, the immunomodulatory effects of vitamin-E (100 mg/kg feed) and commercial probiotic consortia, Rhodomax™ (5 g/kg feed) on the innate immunity of

Objective: To study the ecology of antibiotic resistant bacteria with emphasis on sucrose negative vibrios in water and sediments samples of traditional shrimp farming system (bhery) in West Bengal, India. Methods: The vibrios were isolated from traditional shrimp farm samples on thiosulphate citrate bile salt sucrose agar and sucrose negative bacterial strains were used as biomarkers to assess the frequency of antibiotic resistance. Results: The incoming water brought presumptive vibrios ranging from 5.50000×10 1 to 1.00×10 3 mL in to the bhery, and there appeared to build up vibrios in the culture system with days of culture, as there was about 9 fold increase in vibrios. The levels of vibrios were observed to be moderately higher in outlet water and ranged between 4.15×10 2 and 4.15×10 3 mL. The counts of vibrios in pond sediment was found to be 1.00×10 2 –4.90×10 3 g; while in inlet (2.00×10 2 –4.20×10 4 g) and outlet (3.00×10 2 –6.85×10 3 g) their levels were observed to be higher than the pond sediment. Thirteen different Vibrio species were encountered in traditional shrimp culture system and all vibrios were sensitive to chloramphenicol, followed by ciprofloxacin and gatifloxacin (98.24%), gentamicin (95.61%) and other antibiotics. The multiple antibiotic resistance (MAR), i.e., resistance to at least two antibiotics, was noticed among 43.85% of the sucrose negative vibrios and 41.86% of the sucrose negative non-vibrios. All vibrios harveyi strains exhibited MAR. Although no antibiotic was used in the bhery, the prevalence of MAR in 44% of the sucrose negative vibrios and nonvibrios is a cause of concern. The MAR index was higher in inlet water and sediment samples. The MAR observed in biomarker strains of pond water and sediment (40%) was comparable to those of inlet samples, thus confirming the fact that incoming water was the major source of antibiotic resistant bacteria. Conclusions: It seems that the shrimp culture in bhery does not favour the proliferation and spread of antibiotic resistant bacteria.