WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2024 47 as high as 80 to 100 percent, and wild populations are showing rates between 19 and 33 percent, confirming the virus is spreading beyond farms (Ganesan et al. 2023). Infected crabs show signs of discoloration, slow movement, and severe damage to the hepatopancreas. Our research found viral inclusions in the crabs’ tissues, and TEM analysis revealed viral particles of 70 to 75 nm in size. To make matters worse, many farms are dealing with co-infections of Staphylococcus saprophyticus, a bacterial pathogen that is making the situation worse (Figures 1 and 2). Key Findings and a Possible Solution Our research uncovered that MCRV spreads primarily through cannibalism among crabs. Once an infected crab is eaten by a healthy crab, the virus moves quickly to the next. Waterborne transmission, on the other hand, is minimal. This discovery has given us a direction, by preventing crabs from coming into contact with one another, we can slow the spread of the virus. These research findings are available as a preprint as of now (Nivas et al., 2023). One promising solution is cage (box) culture, which isolates crabs from each other and prevents the cannibalism that drives MCRV transmission. Cage culture could reduce crab mortality by up to 60 percent compared to traditional open pen systems (Nivas et al. 2024). But this solution isn’t easy to implement. Farmers need training and resources to switch to cage culture, and the effort required to roll out this system on a large scale is enormous. Without proper education and disease monitoring, the entire industry could still collapse (Figures 3 and 4). Our Efforts to Turn the Tide In response to this growing crisis, our team, under the guidance of experts, including Drs. Ayyaru Gopalakrishnan, Dinesh Kaippilly and Dung Le Viet, have been working on a Recirculating Aquaculture System (RAS) specifically designed to protect mud crabs. This system offers a controlled environment where biosecurity is the top priority. With advanced filtration systems and limited exposure to outside water sources, the RAS greatly reduces the chances of viral contamination. The RAS is not just a stopgap system—it is a longterm solution for the future of mud crab farming. Even with the best technology, this effort will fail without a coordinated national response. We need better surveillance, MCRVfree hatcheries, and stronger biosecurity protocols if we are to save this critical industry. Economic Impact and the Urgent Need for Action Mud crab farming is a lifeline for thousands of smallscale farmers and an essential part of India’s seafood export market. If MCRV continues to spread unchecked, the collapse of this sector would have devastating consequences—not only for the farmers but for the entire economy. Jobs and livelihoods are on the line. With only one active hatchery struggling to keep up with demand, the situation is getting worse by the day. The Role of International Collaboration This crisis is not India’s alone to solve. The issue demands international attention. Countries that have dealt with similar situations must step forward and share their knowledge. Global collaboration is vital for creating effective biosecurity strategies and disease management plans. Together, we can prevent MCRV from spreading to other regions and protect the future of aquaculture worldwide. The Future of India’s Mud Crab Industry India’s mud crab industry stands at a critical juncture. Without immediate action on a national and international scale, this oncethriving sector could collapse entirely. The adoption of solutions like FIGURE 4. Glimpses of our work in developing a sustainable mud cab RAS unit. Mud crab farming is a lifeline for thousands of small-scale farmers and an essential part of India’s seafood export market. If MCRV continues to spread unchecked, the collapse of this sector would have devastating consequences—not only for the farmers but for the entire economy. Jobs and livelihoods are on the line. With only one active hatchery struggling to keep up with demand, the situation is getting worse by the day. (CONTINUED ON PAGE 48)
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