A total of 481 samples, including 417 shrimp and molluscan shellfish samples from retail shops and farms and 64 water samples from shrimp and molluscan shellfish farms in the Mekong Delta located the southern part of Vietnam, were examined for the presence of Vibrio parahaemolyticus (Vp_AHPND) caused acute haepatopancreatic necrosic disease (AHPND) in shrimp. Vp_AHPND strains were isolated in two of 298 (0.7%) molluscan shellfish samples from retail shops, seven of 71 (9.9%) shrimp samples from shrimp ponds, and two of 42 (4.8%) water samples from shrimp ponds. Vp_AHPND strains were classified into two types of O antigen, including O1 and O3, in which O1 was the predominant. Vp_AHPND strains isolated showed high resistance rates to colistin (100%), ampicillin (93.8%), and streptomycin (87.5%). These results indicate that Vp_AHPND is widely prevalent in environment in the Mekong Delta, Vietnam.

Acute hepatopancreatic necrosis disease (AHPND) has recently emerged as a serious disease of cultured shrimp. A total of 19 lactic acid bacteria (LAB) strains isolated from shrimp samples were characterized based on morphological characteristics, biochemical tests, sequencing analysis, and their ability to antagonize Vibrio parahaemolyticus, which causes AHPND in whiteleg shrimp. Results from the agar well diffusion method indicated that 3 out of 19 isolated LAB strains showed the highest antagonizing ability against AHPND V. parahaemolyticus strain with an inhibition zone diameter ranging from 18 to 20 mm. Experiments where shrimps were given feed supplemented with these LAB strains and challenged with AHPND strain showed high survival rates (approximately 80.0%), which were not significantly different as compared to those recorded in the negative control treatment (86.6%), but significantly different to those recorded in the positive control treatment (40.6%) after 16 days of the experiment. However, the histological images of shrimp hepatopancreas indicated that the infection rate significantly reduced from 60.0% to 11.1% in shrimps fed with LAB-supplemented feeds and challenged with AHPND V. parahaemolyticus strain as compared to those in the positive control treatment. A polymerase chain reaction (PCR) and 16S rRNA gene sequencing confirmed the identification of LAB strain. These results can be applied in further experiments to investigate the ability of L. plantarum in preventing AHPND in intensively cultured whiteleg shrimp.

This study aimed to evaluate the growth, survival rate, and resistance to acute hepatopancreatic necrosis disease (AHPND) of white leg shrimp (Penaeus vannamei) by using Lactobacillus plantarum, Lactobacillus fermentum, and Pediococcus pentosaceus mixed with feed, and at the same time supplying CNP in a ratio of 15:1:0.1 to the water. As a result, the treatments that shrimp were fed with feed containing lactic acid bacteria (LAB), especially L. plantarum, have increased shrimp growth, total hemocyte cells, granulocyte cells, and hyaline cells significantly (p < 0.05) in comparison to the control group. The supply of CNP to the water has promoted the intensity of V. parahaemolyticus effects on shrimp health and significantly decreased total hemocyte cells, granulocyte cells, and hyaline cells by 30–50% in the period after three days of the challenge, except in L. plantarum treatment, which had only a 20% decrease compared to other treatments. In CNP supplying treatments, the AHPND infected rate and mortality of shrimp were higher than those in other treatments. In summary, the supply of CNP had significantly reduced the shrimp’s immune response and promoted the susceptibility of shrimp to AHPND in both cases of use with and without LAB-containing diets.

Background: Alternative materials for antibiotics used in white leg shrimp farming were extensively investigated. The promising effects of plant based extracts in controlling aquaculture diseases has been reported elsewhere. This study was conducted to examine the effect of Solanum procumbens Lour. extract on survival, growth performance, innate immunity and protection against acute hepatopancreas necrosis disease caused by Vibrio parahaemolyticus (VpAHPND) in white leg shrimp. Methods: From March 2021 to September 2021, four difference diets were examined including the supplementation of S. procumbens L. extract at 0.0%, 0.5%, 1.0% and 1.5%. After 30 days of culture, the experimental shrimp was examined for survival rate, growth responses, innate immune parameters and mortality as challenged with VpAHPND. Result: The results indicated shrimp fed diets with and without S. procumbens L. extract supplementation showed no significant differences in survival and growth performances. However, the innate immune parameters were likely increased in shrimp fed diets at 1.0% and 1.5% extract supplementation and shrimp fed diets at 1.0% and 1.5% extract supplementation reduced the accumulate mortality of VpAHPND challenged shrimp by 47.6%. S. procumbens L. could be a potential material for enhancing innate immunity of white leg shrimp and can protect shrimp from AHPND infection.

Background: The high density of farmed snakehead fish and the expansion of the farming area might cause a negative impact on water environment and an increased frequency of fish diseases. The use of plant-based extracts has been promised as an alternative method to antibiotic application in the controlling of fish diseases. This study was conducted to investigate the effect of Pleurotus ostreatus extract on survival, growth, immune responses and against Aeromonas hydrophila of snakehead fish (Channa striata). Methods: During 2021-11 to 2022-10, the P. ostreatus extract was prepared using hot water method and the fish fed diets supplemented the extract at 0.0 g kg-1, 1.5 g kg-1, 2.5 g kg-1, 3.5 g kg-1 and 4.5 g kg-1 was examined for survival rates, growth responses, white blood cell count, respiratory burst activity and mortality rates of fish in A. hydrophila infection. Result: The results indicated snakehead fish fed five different diets showed no significant differences in survival and growth performances. However, the innate immune parameters were likely increased in fish fed diets supplemented P. ostreatus extract and the diet supplemented extract at 4.5 g kg-1 could reduce the accumulate mortality of snakehead fish challenged with A. hydrophila. P. ostreatus extract could be a promising material for enhancing the innate immunity of snakehead fish and can protect fish from A. hydrophila infection.

Background: Enterocytozoon hepatopenaei (EHP) has been caused the substantial lost of production in shrimp farms in Vietnam. This study investigated the prevalence of EHP in white leg shrimp (Litopenaeus vannamei) culture in Vinh Long province, Vietnam and examined the effect of bamboo charcoal on survival, growth and EHP control in white leg shrimp. Methods: A total of 58 shrimp samples collected randomly from 58 shrimp ponds at 53 shrimp farms in Vinh Long province was examined for the prevalence of EHP. Beside that, feed supplemented bamboo charcoal (FSBC) at 0%, 1% and 2% was examined for their effects on survival and growth of white leg shrimp and EHP control in white leg shrimp culture. Result: This study found that EHP can be detected in 28/58 (48.28%) in white leg shrimp samples collected from shrimp ponds. Common clinical symptoms of EHP infected shrimp showed slow growth, size variation, segmented intestinal food and pale hepatopancreas (HP). Several EHP positive samples were found with white feces syndrome. After 3 weeks of culture, FSBC showed no effect on survival and growth of white leg shrimp. After 2 weeks fed EHP infected tissue, shrimp fed bamboo charcoal showed significantly higher survival rates compared to animals fed feed without bamboo charcoal and the cycle threshold value by real time PCR in shrimp fed FSBC at 2% was significantly higher than that in shrimp fed feed without bamboo charcoal. In conclusion, EHP was prevalent relatively high in white leg shrimp ponds in Vinh Long province, Vietnam and bamboo charcoal could be a potential source in EHP control in white leg shrimp culture.