This disease advisory describes the history, known host range, clinical signs and PCR detection methods for decapod iridescent virus 1 (DIV1). Preventative strategies are suggested. Currently known susceptible species of DIV1 include Penaeus vannamei, Macrobrachium rosenbergii, Exopalaemon carinicauda, M. nipponense, Procambarus clarkii, and Cherax quadricarinatus. Clinical signs of infected P. vannamei are not typical, including slightly reddish body, hepatopancreatic atrophy with colour fading, and empty stomach and guts.

In this issue:

Urgent warning: Positive PCR detection results for infectious myonecrosis virus (IMNV) and decapod iridescent virus 1 (DIV1) in captured Penaeus monodon from the Indian Ocean; COVID-19 news; Urgent announcement on usefulness of the lymphoid organ (LO) as an additional prime target for diagnosis of decapod iridescent virus 1 (DIV1) in diseased P. vannamei; Fresh or frozen seafood?; Report of the Eighteenth Meeting of the Asia Regional Advisory Group on Aquatic Animal Health; COVID-19 fallout could push half a billion people into poverty in developing countries; Simple techniques double crablet production.

Due to the devastating impacts of the COVID-19 pandemic the conference has been postponed. New dates have not been set, but it is anticipated that the meeting will be held in 2021 when circumstances allow. The venue will remain Shanghai, China. In the meantime, work on the programme will continue. Updates will be posted in due course.

Crab farmers will be happier, and the environment hopefully better, with recent improvements at the mangrove crab hatchery of SEAFDEC/AQD in Iloilo, Philippines. Crablets used in the farming of the prized mangrove crabs, Scylla serrata, are usually collected from the wild and increasing demand has threatened their natural population. However, Huervana recently revealed that simple tweaks in protocols at the SEAFDEC/AQD hatchery have led to a significant boost in their crablet production, with survival increasing twofold.

This report was prepared by the 18th Asia Regional Advisory Group on Aquatic Animal Health (AG) that met at Bangkok, Thailand on 18-19 November 2019. The group discussed OIE standards and global issues, review of regional disease status, reports on the aquatic animal health programmes of partner agencies, and disease reporting.

From a survey of wild, adult Penaeus monodon of potential broodstock size from the Indian Ocean in April 2018, we obtained positive nested RT-PCR test results for infectious myonecrosis virus (IMNV) and positive nested PCR test results for DIV1. As a confirmatory step, a second round of nested PCR tests was carried out using new, in-house primers designed from regions of the respective viral genomes distant from the target regions used in the first round of tests. These results suggested the possibility that the grossly normal, PCR-positive captured P. monodon specimens might be infected with the respective viruses at the carrier level. If so, they might serve as potential vehicles for introduction of IMNV and/or DIV1 into crustacean culture systems, especially if they were used in hatcheries for production of PL for distribution to shrimp farmers without proper precautions in place.

We carried out laboratory injection challenges that employed extracts prepared from shrimp naturally-infected with decapod iridovirus 1 (DIV1). We found that diseased shrimp from the injection trials showed pathognomonic lesions for DIV1 in the hematopoietic tissue that matched those reported for DIV1 in P. vannamei from China (Qiu et al. 2017. Scientific Reports. 7). In addition, we also found distinctive lesions in the lymphoid organ that could be used as an additional indicator in confirming diagnosis of DIV1 disease. Also, the lesions from shrimp challenged with the 10x dilution were more severe than those from 100x dilution, and for some shrimp in the 100x dilution, the lesions were very clear in the LO but absent in the HPT. Altogether, the results suggested that histology of the HPT and LO could be used together to help in the diagnosis of DIV1 in conjunction with RT-PCR, amplicon sequencing and in situ hybridization (ISH) analysis. This is particularly important in confirming the presence of virulent isolates of DIV1 in new geographical locations.

In this issue:

Mahseer sanctuaries of Meghalaya: A conservation and recreational perspective; Impacts of climate change on aquaculture in Vietnam: A review of local knowledge; Simple means of water aeration adopted by progressive fish breeders in West Bengal, India; Breeding striped snakehead (Channa striata) using the concrete tank method in the Cangkringan Area, Special Region of Yogyakarta; NACA Newsletter.

This article presents available information regarding the present status of chocolate mahseer and the conservation measures been undertaken in the East Garo Hills of Meghalaya. A total of 54 sanctuaries have been established since 2012 in Garo, Khasi and Jaintia hills under the Meghalaya State Aquaculture Mission project of the Fish Farmers Development Agency. The sanctuaries have been established with the objective to preserve and enhance aquatic biodiversity, protect indigenous fish species, preserve breeding and feeding grounds, and serve as tourist attractions to provide livelihood opportunities.

Vietnam has a vast coastline which exposes it to typhoons and flooding. Farmers are at the frontlines of experiencing climate change as their livelihoods are intrinsically linked with the natural environment. Our study collected local knowledge of aquaculture farmers living in South Central Vietnam. The purpose of the interviews was to gather firsthand knowledge on current climate change impacts experienced by farmers, as well as which climate change threats they are most concerned about, and how they are adapting to these threats.