Andy Shinn, director of Fish Vet Group Asia, and a world-renowned expert in aquatic parasites, believes the shrimp industry can do more to mitigate the impact of disease challenges.
Common Shrimp Diseases Today
The top three shrimp pathogens currently are:
- WSSV (White Spot Syndrome Virus)
- AHPND (Acute Hepatopancreatic Necrosis Disease)
- EHP (Microsporidian Enterocytozoon hepatopenaei).
An aerial view of a shrimp pond in Pau Badia, Thailand
Factors that may contribute to increased disease incidence
- Farm management: The majority (about 80%) of farms in Asia are small-scale, with no mandatory disease testing for shrimp leaving hatcheries and stocked into ponds.
- Water management: Many pond systems share water sources. The challenges in maintaining biosecurity for water sources are also greater as they depend on the biosecurity level of surrounding ponds.
- Biosecurity: Depending on the scale of the farming system, implementing biosecurity measures can be very difficult or costly.
- Health monitoring: The rate of shrimp health checks is generally low. Some places offering free diagnostic services have somewhat improved the responsibility of health management. The lack of mandatory culling for diseased ponds has led to higher pathogen persistence and spread.
Some preventive management initiatives to reduce pathogen challenges
- Ponds should be lined with polyethylene sheeting
- Install siphon pits to collect and remove waste, uneaten feed, molted shrimp shells, etc.
- Better pond bottom management through siphoning, observing sludge accumulation, and installing aeration devices to ensure a clean pond bottom.
- Regular cleaning of the pond liner
- Water treatment before stocking into ponds and during the culture period
- Install crab barriers around the pond banks and predator bird netting
- Stock genetically selected shrimp postlarvae for higher disease resistance.
PCR sampling at Fish Vet Group's laboratory in Chonai, Thailand
During the culture period, some aspects need to be closely monitored and managed as follows
- Be aware of shrimp diseases
- Disease testing before stocking and throughout the culture period
- Enhance biosecurity
- Use functional feeds containing health-boosting ingredients
- Culture specific pathogen-resistant shrimp strains
- Closed-system farms are less susceptible to disease and have better on-site water management.
A study was conducted to examine the likelihood of disease outbreaks, production intensity, and investment in biosecurity measures. In low-intensity production systems with low biosecurity and a high probability of disease, losses are typically low when an outbreak occurs. Conversely, for high-intensity production systems with high investment in biosecurity and a low probability of disease, losses can be very high if an outbreak occurs.
Eradicating major shrimp pathogens is very difficult. Some agents are very common bacteria and viruses, and eliminating them is impossible. As aquaculture activities continue to increase, there is greater environmental pressure on viruses and bacteria. The ability of viruses to mutate and bacteria to acquire alternative virulence factors to alter existing pathogens is also a concern. This can lead to the emergence of new strains with significantly increased virulence.
The best we can do is develop better management and control programs to reduce the intensity and frequency of pathogens
- Implementing new technologies and better management can help mitigate risks and create more sustainable systems.
- Record growth data and analyze it to increase farm efficiency.
- Genetic technology to breed healthier, more disease-resistant shrimp.
- Use highly sensitive diagnostic methods. Detecting pathogens at lower levels will help with early detection and simultaneous diagnosis of multiple diseases.
- In-pond sensors – using eDNA methods to monitor livestock health and early detection of pathogens.
- Improve standards in commercial production. For example, ending eyestalk ablation to stimulate maturation.
Source: The fish site
