Best Management Practices for Bio security & shrimp Health Management

Bio security is preventing the introduction, establishment and spread of unwanted biological organisms or agents. In the context of shrimp farming, bio security is about managing dangerous disease risks. Bio security programs can be applied

At several levels, including pond, farm, locality and so on, up to national levels. Bio security measures should be part of every shrimp farm’s health management program. Shrimp farm bio security involves applying sets of targeted, science-based procedures t eliminate or reduce the risk of a particular pathogen that is, a disease-causing infectious agent such as a virus-

1. Entering the farm, and
2. Spreading within a pond, between ponds, to other farms, or to the wider environment.

Because of the costs (in time and money), many farmers generally implement bio security programs to reduce the risks associated only with dangerous pathogens. In an ideal world, they might aim for zero risk, but in reality they will need to balance the costs of any bio security program against the uncertain costs of future disease outbreaks. Development and implementation of a biosecurity program therefore requires a clear appreciation of the technical issues and involves compromises in which costs and benefits must be carefully considered.

Effective will implementation requires long-term commitment from the farmer as well as discipline form the farm workers. Effective bio security relies on a secure farm design, hygiene and quarantine, regular health testing, record keeping, and control of disease vectors. Using specific pathogen free (SPF) seed is the first important step in reducing risk.

Key Instructions for Bio security Implementation and Shrimp Health Management:

1. Stock only post larvae that have acceptable test results in terms of pathogen absence. Do not exceed optimal stocking densities. Eliminate or reduce risk form potential vectors (infection carrying agents) on the farm. Use water management practices that prevent or reduce contamination by the pathogen. Reduce the risk of spreading infection between ponds by restricting movements of people, equipment and other possible agents. Implement a health management program that aims to minimize stress to prawns by optimizing the pond environment.
2. Install Physical barriers to prevent crabs, birds and other animals. To protect form crabs, pond should be covered with crab fence (gill nets with mesh size of less than 1cm) of more than 0.5 meter height. To avoid the contamination form birds, bird net should be provided at the height of 2m from the dyke. Red colored plastic wire with 0.5mm thickness is preferred. The gap between bird lines should not be more than 10cm. There should not be any gap between crab fence and bird fence. It is preferable to provide the fence around all the farms in the neighborhood to avoid the animals, which any lead to cross contamination. Care should be taken not to obstruct to access to pathways for local community.
3. Follow farm sanitation and hygiene. Areas surrounding the farm should be kept clean. Garbage and other farm waste need to be managed through recycling and biodegradation. Each Society should have a toilet in good sanitary condition, and toilet should be located 20 to 30 m away from farm areas. Farm must avoid contamination of domestic sewage into grow-out pond, reservoir and canal. Do not use any animal manure. Provide the disinfect solutions like bleached water of KMnO4 (one table spoon for 10 L water) in one container and plain water in another container at the entrance of each pond. Workers should dip their hands and legs in KMnO4 solution before moving from one pond to another even during the check tray observation. Use separate, marked equipment for each pond (nets, feed buckets, water sampling jars, feeding float etc.) to eliminate the risk of contamination between ponds.

In case separate equipment are not available disinfect them with bleached water or KMnO4 solution (One table spoon for 10 L water) before using in another pond. Each pond should hav3e a separate water sampling container. Maintaining a healthy pond bottom is essential. Check the pond bottom on weekly basis and remove any black soil or benthic algae accumulated at pond corners. Do chain dragging to get organic matter oxidized.

4. Assess the health of shrimp by checking feed trays on daily basis. If there is poor feed consumption for consecutive three to four days, it indicates health problem of shrimp. CHECK the general health and growth of shrimp collected by cast net in weekly basis. Carry out sampling during early morning or late evening at different places. The shrimp should be clean with normal colour, have a full gut and without infection of legs or antennae. Gut content of >80% of the shrimp sampled form a healthy, recently fed pond should be full of food. If not, it could be an indication of onset of disease. If there is antennae cut without black tip, check under feeding. If the gills of shrimp and black it means that the pond bottom is not clean. Check shrimp for external fouling i.e. is growth of organisms and accumulation of debris on the surface of the shrimp. Improve water quality to encourage shrimp to moult regularly. Check if the shrimp have black spots. The causes could be localized bacterial infections like Vibriosis, Fungal infections (e.g. Fusarium species), high nitrite levels, acidic water.

Shrimp coming to the side or surface of the pond, lethargy, lack of appetite, discoloration-either red or blue are all symptoms of potential disease. Improve pond water quality. If shrimp have dirty or black gills, reduce feeding and exchange 10cm of water. Check the pond daily during early morning hours for sick or dead shrimp or other signs (oxygen problems or any other unusual observations).

If there is antenna cut, fouling or gill problem, corrective measures to improve general pond condition should be carried out. If the size of the shrimp is harvestable, harvest all the shrimp without draining the water. Disinfect the affected pond with 20ppm chlorine. Keep the water for one week without discharge. When the disinfected water is discharged after a week, inform neighboring farmers and ensure that water is not pumped in at least for two days. Put up bird net to prevent birds picking up dead shrimp and carrying it to other ponds.

Care should be taken to collect all the shrimp in the pond to prevent spread of disease. Dead and moribund shrimp should be buried under soil away from the pond area. Necessary precautions should be taken to avoid transfer of shrimp or equipments or anything used in the disease- affected pond to other ponds. Do not stop feeding the normal ponds during disease outbreak. Without feeding, shrimp get weak and susceptible to disease. Cooperation and communication with neighboring shrimp farmers and farm workers should be practiced with regular meetings on disease problem to prevent the spread of disease.

Source : NaCSA