Fish Farm Bio-Security
The intensification of fish production provides an ideal environment in which disease-causing organisms can flourish and cause serious damage to productivity. Disease can come from a number of sources i.e. viruses, bacteria and fungi. However caused, it is spread by recognised vectors of infection. These include fish stock, staff and visitors, equipment, vehicles and transportation, other aquatic life, birds and animals, the aquatic environment and even the air itself.
Medication and vaccination have traditionally played a major role in treating diseases but it is now widely accepted that they cannot, in isolation, prevent losses due to disease. Modern farming demands a holistic approach. If the background challenge from disease cannot be controlled, and good management practices strictly followed, medication and vaccination alone are not capable of adequately protecting fish stocks. Fish require an environment in which the level of infection is controlled to the point where vaccination and medication can achieve beneficial effects. Biosecurity is the key to achieving this.
Biosecurity involves the exclusion of disease-causing organisms from the environment. This is particularly important in fish production. It is achieved by the use of external and internal biosecurity barriers:
- External Barriers - blocking the spread of disease onto and off a fish farm
- Internal Barriers - blocking the spread of disease within the fish farm
The correct use and selection of disinfectants is very important and ensures that pathogen challenge is minimised, maximising the fish's natural defence against infection. This in turn will dramatically reduce incidences of disease, reducing mortality and saving money.
There are three key factors that must be considered when selecting a disinfectant for fish farm biosecurity, these are:
- Environmental Impact
- Operator Safety
Not all disinfectants are effective against the wide range of viral, bacterial and fungal disease causing organisms that affect fish production. Disinfectants with similar chemistry can have a widely different spectrum of activity and effective dilution rates.
Selecting a disinfectant is therefore very important. Viral disease agents such as Infectious Anaemia Virus (ISA) are extremely persistent and difficult to destroy. The disinfectant must have proven efficacy against a wide range of aquaculture pathogens and be effective in low concentrations and at low temperatures.
As well as being effective, it is important that the disinfectant causes no harm to the environment in which it is being used.
Viru-Gard is environmentally friendly. Therefore, unlike most other disinfectants where strict discharge controls are essential, use of Viru-Gard will not constrain your daily activities.
Given the exposure limits and dangers associated with the use of some disinfectants, particularly those based on Gluteraldehyde or Formaldehyde, consideration must be paid to operator safety. Viru-Gard has no occupational exposure limits and at a 1% in use dilution is classified as non-irritant to skin and eyes.
Viru-Gard provides complete control for all aspects of fish farm biosecurity.
Shrimp Production Biosecurity Programmes
Disease problems have been an increasing threat to shrimp farming all over the world. Although much needs to be done to investigate shrimp diseases, there would appear to be a progressive pattern of disease occurrence involving viral pathogens that either evolve from prevalent strains or from the introduction of new ones.
Whilst the fundamental issues of shrimp farming are common throughout the world, there are differences in procedures and in particular there are differences in water quality depending on the geographical location of the farm. These differences are reflected in the varying recommendations for product concentrations and application rates throughout the world. It is important to consider the local conditions and experience gained in the various countries before embarking on a full biosecurity programme:
Shrimp Production Biosecurity Programme for Asia
Biosecurity Measures for the Shrimp Industry
The main emphasis of any biosecurity programme is always going to be in the hatchery and in the growing ponds. However, besides good pond management and pond treatment there are biosecurity measures which should be put into place:
- Establish a secure Biosecurity perimeter to ensure that the site is limited to one combined entrance and exit, restricting access to the hatchery or farm to authorized personnel only.
- Ensure that all vehicles have been cleaned and disinfected prior to arrival at site.
- Identify all vectors that can transmit disease from one place to another. Man is a major source of contamination. Anybody working with shrimp in several ponds should wash his/her hands, legs and feet with a 0.5% solution of Viru-Gard solution after handling equipment or stock before moving to work on the next pond. Other vectors of disease transmission include mice and rats and wild birds which can contaminate food supplies and the water in ponds. These vectors should be kept to an absolute minimum.
- Do not share boots or other equipment between ponds unless necessary. In these cases, disinfect all equipment with a 0.5% of solution of Viru-Gard prior to being re-used.
- Provide foot and wheel dips filled with Farm-Gard at 1:100 (1%) or Viru-Gard at 1:100 (1%) and ensure that they are changed every 7 days.
- Minimise the occurrence of rodents and wild birds around the proximity of the farm.
- Where possible clean all surrounding areas of the hatchery or farm (especially if concreted) such as loading bays, paths and roadways with a heavy-duty detergent such as Quat-Gard at 1:500 (0.2%).
- After cleaning, disinfect all surrounding areas of the hatchery or farm such as loading bays, paths and roadways with Viru-Gard at 1:200 (0.5%).
- Thoroughly clean all equipment such as sampling jars and nets, rinse with clean water and then disinfect with Viru-Gard at 1:100 (1%).
The Shrimp Hatchery
Based on applications in Asia the water in hatchery ponds can be treated.
For routine treatment of water add 6 grams of Viru-Gard per 10,000 litres of water. This is a very low inclusion of Viru-Gard but is safe for the developing larvae and post larvae. At this concentration bacterial levels - especially vibrio - will be kept to an acceptably low level. Repeat daily.
When a bacterial challenge is experienced add 10 grams of Viru-Gard per 10 000 litres of water. Repeat daily.
Add the required quantity of Viru-Gard to a small volume of water (approximately 200 mls), mix thoroughly and add to the main tank.
For general water stock used for cleaning equipment add 10 grams of Viru-Gard per 10000 litres of water. Ensure that any equipment cleaned within this stock solution is left for at least 10 minutes before being removed and dried.
For a pond of 1600m² and 1 metre deep add 0.5 kg of Viru-Gard.
This application rate is ideal for the control of both bacteria and viruses. Dissolve 0.5 kg of Viru-Gard in approximately 30 litres of water and add directly to the pond or ideally pour in front of the paddle wheels (aerating device).
For routine control of bacteria and viruses in a 1,000m² pond with a 1 metre depth add 0.5 kg of Viru-Gard. Repeat every 15 days.
Further Biosecurity Measures
There are host organisms that may require the use of smaller mesh filters to keep them from entering the pond. Particular attention should be placed on drains and their communication with the main pond.
The design of a farm is also very critical. It is important to establish a well defined flow of traffic - both personnel and vehicles - within the compound. Foot dips and shoe exchange is recommended before entering any restricted areas. Although costly to initiate, parking areas and foot traffic pathways should be paved and construction materials selected with ease of cleaning and disinfection in mind. Concrete is probably one of the best choices.
Stress is another factor to be carefully managed. Any changes in salinity, pH, temperature, oxygen levels, nutrition, water column levels, excessive bacteria counts, etc can cause stress to the shrimp. These criteria alone may increase the mortality of the shrimp population but any one of these will be more significant with the prevalence of disease - no matter how small.
Note on Aquaculture images: © 2000 ArtAsia Press Cº Ltd. Permission given for use by Graham Doven