Abstract
Shrimp, as a high-protein animal food commodity, are one of the fastest growing food producing sectors in the world. It has emerged as a highly traded seafood product, currently exceeding 8 MT of high value. However, disease outbreaks, which are considered as the primary cause of production loss in shrimp farming, have moved to the forefront in recent years and brought socio-economic and environmental unsustainability to the shrimp aquaculture industry. Acute hepatopancreatic necrosis disease (AHPND), caused by Vibrio spp., is a relatively new farmed penaeid shrimp bacterial disease. The shrimp production in AHPND affected regions has dropped to ~60%, and the disease has caused a global loss of USD 43 billion to the shrimp farming industry. The conventional approaches, such as antibiotics and disinfectants, often applied for the mitigation or cure of AHPND, have had limited success. Additionally, their usage has been associated with alteration of host gut microbiota and immunity and development of antibiotic resistance in bacterial pathogens. For example, the Mexico AHPND-causing V. parahaemolyticus strain (13-306D/4 and 13-511/A1) were reported to carry tetB gene coding for tetracycline resistance gene, and V. campbellii from China was found to carry multiple antibiotic resistance genes. As a consequence, there is an urgent need to thoroughly understand the virulence mechanism of AHPND-causing Vibrio spp. and develop novel management strategies to control AHPND in shrimp aquaculture, that will be crucially important to ensure food security in the future and offer economic stability to farmers. In this review, the most important findings of AHPND are highlighted, discussed and put in perspective, and some directions for future research are presented.
Highlights
The acute hepatopancreatic necrosis disease (AHPND) is caused by specific strain of bacteria, e.g., V. parahaemolyticus, V. punensis, V. harveyi, V. owensii, V. campbelli and Shewanella sp. that contains pVA1 plasmid (63–70 kb) encoding the binary PirAVP and PirBVP toxins, homologous to the Photorhabdus luminescens insect-related (Pir) toxins PirA/PirB (Table 1) [18,39,40,41,42,43]
The results showed that none of the AHPND-causing strains possess tdh, trh or TTSS2-related genes of human pathogenic strains [81]
The results showed that heterotrophic bioflocs and autotrophic bioflocs can decrease the impact of AHPND-causing V. parahaemolyticus and the highest survival of L. vannamei was observed when challenged in the presence of their respective biofloc suspensions
Summary
Economic losses from disease outbreak have been estimated by the FAO to be over of USD 9 billion per year, which is approximately 15% of the value of world farmed fish and shellfish production. The shrimp production in AHPND affected regions has dropped temporarily to ~60% and has resulted in collective losses exceeding an estimated USD 43 billion across Asia (China, Malaysia, Thailand, Vietnam) and in Mexico [23,24,25,26,27]. The shrimp affected with AHPND exhibits lethargy, anorexia, slow growth, empty digestive tract and a pale to white hepatopancreas These reported clinical signs for AHPND are common for some other diseases. Identification of bacterial virulence factor and AHPND-specific cellular changes coupled with gross clinical signs are considered to be helpful for confirmatory diagnosis of AHPND in shrimp
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