Everything you need to know about EMS in shrimp farming - Part 3

Best practices for managing EMS/AHPND

There is no quick fix for EMS/AHPND – once a farm is infected a carefully balanced management plan is required. In a worst-case scenario, farmers should be prepared to harvest all ponds at short notice. There must be a strong commitment by all team members to implement strict biosecurity measures and a thorough disinfection phase to manage the disease and avoid future outbreaks.

Biosecurity is a concept for preventing disease infection and preventing the disease from spreading across boundaries. The two dominant approaches in biosecurity practices are preventive measures – the exclusion of pathogens – and countermeasures that eliminate pathogens. We can manage EMS/AHPND by preventing its further spread and providing better conditions to increase shrimp resistance to it.

Here are some of the best practices for managing EMS/AHPND in infected farms, covering all steps of production.

Preparing for the production cycle

• PL need to be derived from AHPND-free broodstock. The general health of PL should be checked before stocking, including in stress tests.
• All facilities should be disinfected prior to stocking. Using multiple disinfectant agents helps to remove all pathogen vectors.
• The grow-out pond should be lined with HDPE plastic liners for easy cleaning and control.
• Before stocking, ponds should be completely dried. Water should also be conditioned for 10–15 days before the shrimp are stocked.
• A thorough biosecurity plan should be implemented and reviewed after every cycle.
• Protect the farm from outside species, for instance by using crab protecting devices.
• To avoid infection, stocking should be done in a single area at the same time. It is recommended to stock into water which has Vibrio of less than 1 x 10^3 CFU/ml – ie where these species make up less than 1 percent of the total bacteria concentration.

Mitigating EMS during grow-out

• Water quality parameters – including levels of pH, alkalinity, salinity, dissolved oxygen (DO), ammonia nitrogen and hydrogen sulphide – should be monitored regularly.
• Shrimp health should be monitored every three days, this should include cramping and hepatopancreas checks.
• The feeding regime should be adjusted to avoid overfeeding and feeds containing a protein content of over 30 percent is suggested.
• The sediment should be siphoned regularly.
• Proper aeration should be maintained.
• Probiotics should be applied regularly and be increased where stress events or water exchanges occur.
• Agree water outlet and intake regimes with all farms in the area to reduce transferring pathogens between farms.
• At the first sign of disease, a management plan must be enacted. Where disease is suspected, a confirmatory lab test should be used.

EMS can be a devastating disease, but investing in infrastructure, strict biosecurity and frequent farm management reviews can help defend against the disease and reduce its impact if it enters the farm.

Long-term EMS solutions: infrastructure and technology

Maintaining the right equipment and infrastructure on the farm will make biosecurity maintenance and pathogens defense easier, resulting in more stable financial returns. The infrastructure needed to maintain biosecurity and defence against pathogens includes HDPE lining, foot, vehicle and hand wash stations, as well as fencing and netting to prevent people and animals from entering the farm.

Other important infrastructure includes dedicated water inlets and outlets, a central drain, pre-treatment ponds with a volume of at least 30 percent of the grow-out ponds, post-treatment, 10 hp of aeration per 1000m2 with good currents, nursery stages, storage facilities and a basic on-site laboratory with strong lighting for dissection and basic water testing.

There are also emerging technologies that can offer advanced detection and enable better management of pathogens. One company rapidly disrupting what disease detection means for the industry is Genics, which offers a new way to detect pathogens and their density with the Shrimp MultiPath technology. The test can detect disease up to 10 days before clinical signs and subsequent mortalities – buying farmers precious time to decide suitable mitigation strategies as early as possible and reduce the risk of an outbreak.

Moving forward from EMS

EMS can be a devastating disease but – as has been proven in Thailand and Vietnam – investing in infrastructure, strict biosecurity and frequent farm management reviews can help defend against the disease and reduce its impact if it enters the farm. The industry must take a proactive, preventative view to EMS/AHPND as it should to all pathogens, known and unknown. By planning for the worst and operating for the best, farmers have a better chance of producing successful crops, even in areas with high disease prevalence.

In addition to this quick overview on EMS, farmers should read other articles, attend national and international webinars and join local events where they can learn more and share ideas about disease prevention and mitigation.