Review of current disease threats for cultivated penaeid shrimp in Asia

Several shrimp diseases are new or newly emerged in Asia, including acute hepatopancreatic necrosis disease (AHPND), hepatopancreatic microsporidiosis (HPM), hepatopancreatic haplosporidiosis (HPH), aggregated transformed microvilli (ATM) and covert mortality disease (CMD). In addition to these, white spot disease (WSD), yellow head disease (YHD) and infectious myonecrosis (IMN) continue as the most serious viral threats to shrimp farmers in the region. Other diseases such as monodon slow growth syndrome (MSGS), white tail disease (WTD) and abdominal segment deformity disease (ASDD) are of less concern. In contrast, Taura syndrome virus (TSV) and infectious hypodermal and hematopoietic necrosis virus (IHHNV) have become innocuous due to the widespread use of highly tolerant specific pathogen free (SPF) stocks of Penaeus (Litopenaeus) vannamei that dominate production. Similarly, diseases caused by monodon baculovirus (MBV) and hepatopancreatic parvovirus (HPV) appear not to affect P. vannamei. Spread of diseases has been promoted by the use of live or fresh broodstock feeds such as polychaetes and clams. Also, shortages in the supply of imported SPF broodstock led some entrepreneurs to employ post larvae (PL) of imported SPF stocks to produce 2nd generation broodstock in open shrimp ponds where they became contaminated and were then used to produce PL for stocking ponds. These practices left the whole shrimp industry vulnerable to rapid spread of the new and newly emerging diseases and resulted in the current crisis in Asian shrimp culture. The situation has been exacerbated since 2009 by an almost exclusive focus on AHPND, which is only partially responsible for what has been widely called early mortality syndrome (EMS). The purpose of this review is to summarize progress of research on AHPND bacteria and also to encourage a wider focus on additional pathogens that are causing farm losses. The significance of these diseases and their implications for the future of shrimp aquaculture are discussed. Statement of relevance: This review summarizes recent information about new and newly emerging diseases of cultured shrimp in Asia and discusses the biosecurity lapses that led to the current shrimp production crisis. All industry stakeholders must be aware of this situation and of the need for regional and global collaborative efforts to stem this crisis and prevent future development of another. (C) 2015 Elsevier B.V. All rights reserved.