Immunomodulation of Vibrio-Infected Penaeus monodon, Subjected to Probiotic Feed Supplementation

The study was an attempt to assess the impact of induced vibriosis by using Vibrio parahaemolyticus in cultured marine tiger prawn, Peneaus monodon collected from, Nagapattinam. Laboratory investigations were carried out to infer the impact of pathogenic Vibrio parahaemolyticus on total count, differential count, Nitroblue tetrazolium activity, Prophenoloxidase activity and bacterial clearance in Penaeus monodon. Feeds were prepared by coating two putative probiotic strains of bacteria B. firmus and B. coagulans isolated from the gut of wild marine prawn, P. monodon. Total heamocyte count after 30 days of probiotic supplementation was in control animals 1442 cells /Cu.mm, in B. coagulans supplemented animals 2757 cells / Cu.mm and in B. firmus supplemented animals 2448 cell/cu.mm. Differential count of prawn was evaluated by studying the three types of cells hyaline cells (HG), Small granular cells (SG) and large granular cells (LGL). There was not much variation in the percentage of cells, but slight decrease was observed in the hyaline cells after 24 hours of infection. The NBT activity was 1.4 (NBT activity Units/min/mg of protein)in control animals, 2.7 in B. coagulans supplemented animals, and 2.4 in B. firmus supplemented animals. Maximum reduction was observed in control animals with 0.92, 1.7 in B. coagulans supplemented animals, and 1.4 in B. firmus supplemented animals. The prophenol oxidase activity was 1.2 (prophenol oxidase activity Units/min/mg of protein) in control animals, 1.5 in B. coagulans supplemented animals, and 1.4 in B. firmus supplemented animals. Similar to that of differential count in this also there was gradual decrease in prophenol oxidase activity after infection. Maximum reduction was observed in control animals with 0.74, 1.9 in B. coagulans supplemented animals, and 1.3 in B. firmus supplemented animals.Bacterial clearance was enumerated in the heamolymph from the time of injection. There was initial spurt of vibrios when cultured in selective medium TCBS in all three treatments and gradual decrease in the vibrios count during 24 hours observation.