The application of probiotics for disease control in aquaculture is now a convincing approach towards replacement of antibiotics, which can cause adverse effects in aquatic animals and humans. In this study, we combined 2 probiotics, Lactobacillus acidophilus and Saccharomyces cerevisiae, with shrimp feed to create 2 formulas (WU8 and WU9), which were fed for 10 d to juvenile shrimp Penaeus vannamei. The shrimps were then subjected to a challenge infection with Vibrio parahaemolyticus, the causative agent of acute hepatopancreas necrosis disease (AHPND). The protective effects of probiotics against bacterial infection were investigated through histopathology of the hepatopancrease and immunological evaluation of shrimp. Both WU8 and WU9 probiotic mixtures (1:1, at 108 and 109 CFU kg diet-1) increased blasenzellen hepatopancreatic epithelial cells and reduced pathology caused by AHPND. After 10 d of feeding, hemocyte parameters, including the total hemocyte count, percent of granular hemocytes, and phenoloxidase activity, increased significantly and were still increasing at 24 h post infection. Crustin and penaeidin 3 genes were also highly upregulated in hemocytes before and after 24 h of bacterial challenge and significantly upregulated in the hepatopancreas 1 to 5 d post-infection. A significantly higher survival rate was observed in shrimp fed with the probiotic supplemented diet (>90%) in comparison to the control group (60%). In conclusion, probiotic mixtures of L. acidophilus and S. cerevisiae reduced hepatopancreas pathology and protected shrimp from a challenge with AHPND.

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Here single nucleotide polymorphisms (SNPs) were associated with white spot syndrome virus (WSSV) resistance in black tiger shrimp Penaeus monodon. SNPs were identified by single-strand conformation polymorphism (SSCP) screening and DNA sequencing of shrimp sampled from 3 families (100 shrimp per family) challenged with WSSV. Shrimp that died over the 14 d challenge trial were designated susceptible, with those remaining alive on Day 14 designated resistant. To compare SNPs, 10 samples from the susceptible and resistant groups, each comprising DNA pooled from 3 shrimp, were amplified by polymerase chain reaction (PCR) using primers to 12 selected genes and screened by SSCP. SNPs were only identified in the anti-lipopolysaccharide factor 3 (ALFPm3) gene product. Analysis of complete ALFPm3 gene sequences confirmed the existence of 3 SNPs (g.934C>G, g.1186A>G, and g.1898C>G) that were polymorphic between the susceptible and resistant groups. Further analyses using specific tetra-primer amplification refractory mutation system PCR primer sets associated these 3 SNPS, and particularly the g.1186A>G SNP, with WSSV resistance. This SNP thus has potential for use as a DNA marker to select for WSSV resistance in P. monodon breeding programs.

5-aminolevulinic acid (5-ALA) is an endogenous non-protein amino acid that is widely used in medicine, pharmacy products, agriculture, and aquaculture. In this study, the aim is to investigate the effects of 5-ALA on feeding Pacific white shrimp (Litopenaeus vannamei) with a diet supplemented with 5-ALA on their growth performance, immune responses, and resistance to acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio paraheamolyticus. Shrimp were fed with different diets, including a commercial diet (control) and diets supplemented with 15 ppm (ALA15) and 30 ppm (ALA30) of 5-ALA for 15 and 30 days before bacteria challenge. Anti-lipopolysaccharide factor, crustin, and penaeidin3 immune genes had significantly increased expression level after 15 and 30 days of feeding with 5-ALA. The mortality rate of L. vannamei fed with 5-ALA for 15 and 30 days significantly decreased after V. parahaemolyticus infection. These results indicated that the diet supplemented with 5-ALA enhanced the innate immune response and consequently shrimp's pathogen tolerance. Thus, 5-ALA can be used as immunostimulant additive for Pacific white shrimp cultivation.

The farming of Nile tilapia (Oreochromis niloticus) has faced the challenges of infections, especially by Streptococcus However, solving this problem by using antibiotics will cause other problems, such as drug residue that can directly affect consumers and an increase in antibiotic resistance to bacteria. Therefore, probiotics should be an alternative to control bacterial diseases. This study aimed to investigate the optimum level of mixed probiotic supplementation. The experiment was designed to include six treatments (the control diet and probiotic-supplemented diets at 0.5, 1.0, 2.0, 5.0 and 10.0%). The mixed probiotic was composed of 3.1 × 108 CFU of Lactobacillus sp. and 4.6 × 106 CFU of Saccharomyces cerevisiae. After feeding for 30 days, tilapias from each replication were injected with a vaccine containing Streptococcus agalactiae to study the immune gene expression. The results showed that this mixed probiotic can enhance the growth and immune system of tilapias, and the most effective level was at 0.5% with consideration for high ADG, low FCR, and high protective efficiency against S. agalactiae infection. Moreover, toll-like receptor 9 gene and immunoglobulin gene expressions after vaccination for 24 hours were significantly higher than the control. The relative percent survival was the highest at 78.13%. This mixed probiotic can be used for Streptococcosis control in tilapia farms because it can reduce the diet cost and induce both the growth and immune system of tilapias.

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