By Kathleen H. Hartman*
In my first aquaculture course the first lecture was dedicated to definitions and requirements for successful fish rearing. The prime requirement was determined to be “a plentiful supply of suitable quality water” which was dependent on the species being cultured, culture method and type of facility. The lecture went on to describe additional ‘keys to success’ which boiled down to knowledge and skills in animal biology, water chemistry, engineering, economics, and business and personnel management. I think everyone would agree that all these factors continue to be true and all contribute to overall animal health and business success. I would like to tweak out four areas that are ‘keys to success’ in achieving and protecting aquatic animal health on the farm in the broad sense. These areas are 1) access to technical experts both on and off the farm with regards to health and husbandry issues, 2) biosecurity, 3) clear plans for detection, communication and response to health issues and 4) adequate record keeping.
Technical expertise to achieve aquatic animal health
Any aquaculture business invested in the production of live animals should have a cadre of knowledgeable, reliable and trained professionals, veterinary and non-veterinary, working for or readily accessible both on and off the farm. Individuals working with the animals should receive regular training regarding biosecurity, signs of disease and pathogen recognition as well as appropriate husbandry practices and water chemistry parameters. To support these workers on the farm, the facility should also have equipment needed to conduct these activities.
Items on the top of my list for an aquaculture farm are: 1) a quality water chemistry kit that is both precise and sensitive enough for parameters suitable to the species and operation, and 2) a quality compound light microscope with appropriate objectives (recommended powers for objective lens are 4x, 10x and 20x [usually must special order the 20x]). Both of these relatively expensive tools require the person using them to be sufficiently trained on how to use the equipment and then accurately interpret what information is gained from using it. Too often the upfront investment is made in the equipment which then never gets used or is used incorrectly. I have found that employees will not use equipment if they do not understand it, know how to work it or are afraid they will break it. Overcoming these issues simply requires training and regular use of the tools.
Off the farm, the aquaculture business should have contacts with professionals, veterinary and non-veterinary, that can assist with husbandry, health (nutrition, disease diagnosis and treatment, vaccination etc.) and regulatory issues. Ideally, these individuals should have firsthand knowledge of the facility and procedures and practices such that recommendations or changes are not made in isolation. The business should bring all these players together to ensure that the “team” is working together to achieve the business the goal of producing quality healthy animals.
Biosecurity to protect aquatic animal health
The benefits of biosecurity are often intangible and unforeseen until it is too late. A colleague of mine has a presentation slide saying “If you cannot afford prevention, how will you afford disease?” showing a picture of a dump truck load of fish being dumped into a burial pit. The image is pretty effective. Farm biosecurity practices should be effective and meaningful for targeted pathogens. It is unreasonable to expect animals and/or a farm to be free of all disease-causing organisms all the time. But it is possible to mitigate the risks of specific pathogen introduction and/or spread with constant well planned effective strategies. Every facility will have different biosecurity risks but the top five areas to assess for most aquaculture facilities are the 1) animals, 2) water, 3) feed, 4) fomites (inanimate objects) and 5) vectors (a carrier, mechanical or biological, of a pathogen). These can conveniently be remembered on one hand!
Biosecurity will be covered in more detail in a later column but in brief a biosecurity plan should be in writing and detail all the practices and procedures on the farm from animal movement to pest control to carcass disposal.
The plan should be written after a thorough assessment of all the risks specific to the facility. It is no longer sufficient to say, “I have a footbath in the hatchery”; plans should detail why the footbath is there (what is it trying to keep out?), what disinfectant is being used (is it appropriate for the targeted pathogen?), and how often and who is responsible for cleaning and changing the solution? Biosecurity often gets a bad rap because money is spent on expensive disinfectants and equipment that are inappropriately used and the benefit is completely lost. Biosecurity is an ever-changing goal and plans and practices should be regularly evaluated.
Plans for detection, communication and response to maintain aquatic animal health
An aquaculture facility in conjunction with their technical expertise panel should have clear plans, devised as much as possible before a health problem occurs, for pathogen detection, communication of the detection and response to the causative problem(s). This begins with employees on the farm being trained and knowledgeable about the species being reared and recognizing when animals or systems are “ADR” (ain’t doin’ right). Ignoring early signs of a problem is simply diagnosed as “PMD” (poor management disease). Employees should know the early trigger points for when to start an investigation into a potential problem and when to call for help. Facilities may set morbidity or mortality set points that once exceeded, trigger, for example, a hold on the system, sample collection and testing, communication of the issue and then appropriate response whether that is a water change or chemotherapeutic treatment regimen.
The professionals on and/or off-site may be used to help accurately diagnose a problem and plan a response. Furthermore, they can provide guidance on how to prevent reoccurrence of the problem. They may also be able to construct strategies for surveillance on the farm to better manage animal health or to meet standards for declarations of freedom from a disease on the farm.
Records to verify aquatic animal health
Maintaining adequate and appropriate records is not always as easy as it sounds. Questions often arise about what to record, how to record it and then how long to keep it. Answers to these questions will vary depending on the business. A facility needs to devise a system that works for them which achieves compliance with record-keeping without becoming onerous. From a veterinary perspective, water quality parameter data, morbidity and mortality numbers, feed consumption, diagnostic test results, treatment regimens are all important. And from a biosecurity approach, documentation of animal sources, animal movement, feed source, pest control, logs of footbath changes and the like are all critical to be able to verify integrity of the practices. More and more it is not sufficient to simply point to the footbath for proof of use, for example, but there must be written indication about why it is there and how it is managed over time.
How the data is recorded and kept is largely up to the facility unless they are meeting some requirement for a program or trade. The length of record retention may vary depending on business needs and other requirements but for animal health a good rule of thumb is to retain records for at least 2-5 years after the animal(s) have left the facility (dead or sold).
There are many keys to success and achieving, protecting and verifying aquatic animal health takes a team of people working together to ensure its success.
Next column – Early Detection of Health Issues.
Kathleen Hartman, PhD, is the Aquaculture coordinator for USDA APHIES Veterinary Services at the Tropical Aquaculture Laboratory of the University of Florida, USA. She currently serves on the Professional Standards Committee of the American Fisheries Society-Fish Health Section and is a current member of the World Aquaculture Society (WAS).