The Need For Biosecurity in Aquaculture

Disease challenge by viruses, bacteria, fungi and toxic algae presents a major threat to profitable aquaculture production. Biosecurity, in other words reducing the number of infectious organisms in the aquaculture environment, is the most effective form of protection. Biosecurity is a set of management practices, which reduce the potential for the introduction, and spread of disease-causing organisms onto and between sites. Bio-security procedures, particularly disinfection and sanitation, should be combined with selection of pathogen-free seed and strategic treatments to either eradicate or reduce these pathogens to non-infectious levels.

The Neospark Biosecurity Programme has been developed over many years with leading aquaculture producers around the nation. Neospark products and procedures have proven effective in practical farm conditions against a broad spectrum of pathogens. These include persistent and difficult to destroy immunosuppressive viruses causing WSSV, MBV and Vibriosis, which make the shrimps and other aquaculture organisms more susceptible to additional disease challenge. Neospark disinfectants are also proven effective against bacteria casing a threat to food safety such as E. coli, Pseudomonas, Aeromonas, Salmonella, Shigella, Edwardsiella etc.

HACCP (Hazard Analysis and Critical Control Points) principles are increasingly being applied on all stages of aquaculture sector to control such threats. Neospark Bio-security Programmes are entirely consistent with HACCP principles.

Disease transmission

The mode of disease transmission between shrimps/prawns/fishes or between ponds or even between sites may or may not differ depending on the type of infection. For example, the occurrence of WSSV in shrimps depends on several factors. The shrimps that carry WSSV may not show any prominent symptoms or mortalities at all times. This may be due to the number of physico-chemical and microbiological factors, which triggers the stress factors causing severe mass mortalities. 

Therefore the management aspects should be considered for occurrence or non-occurrence of diseases in aquaculture ponds. Subsequently the virus particles through drained water spread the disease by waterborne transmission. On the other hand, the secondary infections caused my bacteria or other microbes, which are native flora, also causing the diseases and heavy mortalities. Infectious agents spread through droppings is also a major threat to the aquaculture sector.

Other diseases persist on sites through the contamination of equipment and organic matter by stubborn virus particles. Many organisms will persist outside the host, and Vibrio, Zoothamnium, Aspergillus and many viruses can survive in this way for a considerable time, especially in organic material.

Factors influencing biosecurity

Infection may be harboured and spread in a variety of ways. In relation to aquaculture, these may include by crustaceans, in feed, in feacal matter, by birds, by inadvertent human intervention and on equipment. These factors all influence the planning of a bio-security programme.

However, disease avoidance measures can be undertaken elsewhere. For example, use a heavy-duty broad-spectrum virucidal and bactericidal disinfectant (eg KloSant or ViraNil, Neospark), which will be capable of dealing with gross organic challenge.

People are the most important animate factor – including employees, servicemen, vehicle drivers, fishermen (cast net sampling). Staff movements should be as limited as possible, particularly where the disease situation on a particular site has deteriorated.

Control site traffic:

Keep to a minimum and exclude all unauthorized persons. All visitors should enter on foot. Use regularly refilled foot dips, charged with a suitable disinfectant (eg. SparkDin, Bionex, ViraNil - Neospark).

All possible vehicles should be excluded from the site. Vehicles, which must enter, should be subject at the site entrance to spray disinfection of wheels and wheel arches. All visitors should observe standard operating procedures on vehicle cleansing and protective clothing used by vehicle crew.

All site visitors should be provided with adequate protective clothing, and should wash their hands prior to visiting ponds. Use an effective hand hygiene system, which is equally effective even when there is no available water supply (KloSant or ViraNil, Neospark). A shower in, shower out facility should also be seriously considered.

The fish or prawn or shrimp themselves can also be a cause of disease spread. Incoming seed should therefore be from high health status sources and there should be a well-defined health monitoring and audit procedure for bravids/broodrs/nauplei supply flocks. This should extend to hatchery hygiene procedures with regular microbiological/PCR monitoring. Avoid the potential spread of infection by diseased carcasses and dead once by on-site incineration.

Effective cleaning and disinfection reduces pathogen numbers and the weight of disease challenge, and enhances any biosecurity programme. It can only be achieved with sufficient turnaround/down time to allow removal of all organic matter or litter, and to satisfy required contact times for the disinfection products used prior to stocking or restocking. Cleaning and disinfection should include ponds, equipment and surroundings.

  

Use water with a low total viable count for better growth of fish, prawn and shrimp. It is always better to maintain a reservoir for ideal disinfection of total volume of water. At turnaround, clean and disinfect the water system with a non-tainting product (eg. KloSant or ViraNil, Neospark) to remove the greasy biofilm that will harbour and protect pathogens.

Treat feed trays and feed delivery systems. Feed delivered to the site must be of high health status and vermin protected. Finished feed and stored raw materials should be sampled regularly for its quality. “High risk” feed or raw materials or sources should not be used.

Check biosecurity procedures regularly. Use only biosecurity products with proven broadspectrum efficacy against all viral and bacterial pathogens and use them according to manufacturers’ instructions. Maintain an effective, audited biosecurity programme and prevent entry of pathogens through good farm/pond design and repair.

Biosecurity Checklist:

01. Properly implemented biosecurity measures will limit the spread of disease causing organisms.

02. When these are combined with disinfection and sanitation, vaccination and strategic treatments, many pathogens can be reduced to non-infectious levels.

03. Remember – different infectious agents spread by different methods, so use appropriate measures against each type.

04. Site location and design, and density of fish/prawn/shrimp in a given geographical area, are vital. When planning a new site, there is the opportunity for very effective biosecurity to be implemented at the design stage. However, biosecurity practices must concern themselves with practicalities, rather than a theoretically deal set-up.

05. All sites must have traffic – in personnel, feed, stock and equipment – but this should be kept to an absolute minimum.

06. Only essential vehicles should have access to a site, and these should be sanitized where possible on arrival.

07. Use protective clothing to prevent pathogen spread.

08. Priority should be given to biosecurity measures on breeding and hatching sites since errors here are magnified greatly at the commercial level.

09. Site decontamination, turnaround times and a well audited and structured cleansing and disinfection procedure should be in place for all sites.

10. Effective disease/pathogen carrier control must be maintained.

11. Only disinfectants with proven broad-spectrum efficacy against all viral and bacterial pathogens should be used and then at manufacturers’ stated dilutions and directions.

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