by Dr. Natthinee Munkongwongsiri
Vibrio species are a group of bacteria that are naturally found in aquatic environments, including seawater and estuaries. They can be pathogenic to shrimp and can lead to diseases such as vibriosis, HLVD and EMS. Shrimp hatcheries, where shrimp larvae are reared before being transferred to grow-out ponds, can be highly susceptible to Vibrio contamination.
Causes of Vibrio Load in Shrimp Hatcheries
- There are several primary factors contributing to Vibrio proliferation in hatchery tanks. While one factor may initially lead to an increase in Vibrio numbers, it can also synergistically amplify the impact of other factors, resulting in a higher Vibrio population.
- Poor Water Quality Management: Inadequate filtration and water exchange can lead to the accumulation of organic matter and nutrients, creating a conducive environment for Vibrio growth. Maintaining optimal water quality is paramount for the health of shrimp larvae, as poor conditions make them more susceptible to Vibrio infections.
- High Organic Load: Accumulation of uneaten feed (due to poor feed management), feces and dead larvae, can elevate the organic load in the water, providing an abundant food source for Vibrio.
- Overcrowding: High stocking densities can induce stress in the shrimp, rendering them more susceptible to bacterial infections, including Vibrio.
- Inadequate Disinfection: Ineffective disinfection of tanks, equipment, water sources, and even the nauplii can allow Vibrio to persist in the hatchery environment. If water sources are contaminated with Vibrio, it can easily introduce the bacteria into the hatchery if not treated adequately.
- Inadequate Biosecurity Measures: Poor biosecurity practices, such as improper quarantine procedures for incoming animals, water, equipment and staff moving between production areas can lead to the introduction and transmission of Vibrio.
Strategies to Control or Reduce Vibrio
Methods for mitigating Vibrio in hatcheries must address the root causes. It is crucial to accurately identify the causes and sources of contamination in order to implement effective solutions.
- Optimize Water Quality: Implement effective treatment and water exchange protocols to maintain good water quality. While water exchange may appear to be the quickest way to reduce Vibrio, it is not always effective as Vibrio may increase faster than less harmful bacteria. For example, some Vibrio can double every 10 minutes compared to Bacillus which may take 1-2 hours.
- Nutrient Management: Properly manage feed application and remove uneaten feed to prevent excess organic matter from accumulating in the water. Feed is the primary source of organic nutrients introduced into the culturing tank. Paying close attention to the feeding program will significantly decrease the available food supply for Vibrio.
- Stocking Density Management: Avoid overstocking to reduce stress on shrimp and minimize the potential for disease outbreaks. When larvae are overstocked beyond the tank’s maximum capacity, it will undoubtedly induce stress, making them more susceptible to infections and ultimately leading to mortality. Subsequently, the dead shrimp will serve as a food source for Vibrio, facilitating its propagation in the tank.
- Disinfection and Sanitation: Regularly clean and disinfect tanks, equipment, and surfaces using appropriate disinfectants to reduce bacterial load. Pay special attention to blind-spot areas. Additionally, it is essential not to rush the stocking of a new batch if the tanks have not been properly sanitized. Routine checking of Vibrio in the water supply is recommended.
- Biosecurity Measures: Implement strict biosecurity protocols, including quarantine procedures for new stock, visitors, and equipment entering the hatchery. Also, within the hatchery, staff members in each unit should have limited access to other units.
It is absolutely imperative to tailor these strategies to the specific conditions and challenges faced by your shrimp hatchery. Speak to our local commercial teams and seek guidance for technical support for valuable insights and assistance.
