Aquaculture is the fastest-growing animal farming sector. It accounts for nearly half of the world’s fish supply and is critical to providing much-needed protein to a growing world population. There has been a worldwide shift from industrial fishing towards fish farming, with populous countries such as China, India, Vietnam, Bangladesh, and Egypt utilizing more aquaculture than wild-caught fish. This form of farming oceans and freshwater basins helps greatly in securing a stable food supply; however, the conditions of fish farms can be hotbeds for maladies that lead to widespread fish deaths.

Traditional disease management in aquaculture has relied heavily on antibiotics for decades. However, in recent years there has been a shift away from many types of antibiotic usage as there are concerns about drug resistance and what that could mean for human beings.

Here, we cover the topic in detail:

How have antibiotics historically been used in aquaculture?
Why are antibiotics being banned globally?
What is advisable antibiotic usage today?
How are farmers adapting to an antibiotic-free industry?

Antibiotic Usage & the Drive for Increased Production

Due to this pressure for production, there has been an industry-wide trend toward higher densities of fish (called “intensification”). In these dense, overcrowded pens and ponds, disease can proliferate. With higher waste levels and few barriers to prevent infected fish from contaminating others, antibiotics became a necessary disease management tool for fish and shrimp farmers.

The Rise of Antibiotic Resistance

The most important issue of using antibiotics in aquaculture is the potential to accelerate the development of antibiotic resistance, which results in a decrease of the effectiveness to treat human infections. Inappropriate and irrational use of antibiotics can lead to the emergence of resistant bacteria. The use of antibiotics in aquaculture is a particular concern because the greater the duration of exposure the antibiotic has in the environment, the greater the risk for the development of resistance - and administration of these drugs into aquatic ecosystems allows them to persist for long periods of time.

Studies from Bangladesh, India, Indonesia, and Thailand have reported antibiotic residues in aquaculture products and aquaculture water. There concentrations were:

Chloramphenicol in Bangladesh - up to 5ng/L
Chloramphenicol in India - up to 32ng/L
Chloramphenicol in Indonesia up to 45ng/L
Erythromycin and tetracyclines in Thailand - up to 180 ng/L
Fluoroquinolones in Thailand - up to 46100 ng/L
Fluoroquinolones in Vietnam - up to 1130 ng/L

But how much do these concentrations affect drug resistance on a more global scale? And to what degree does aquaculture contribute to antibiotic resistance and associated human deaths?

Drug-resistant bacteria claims the lives of more than 35,000 people in the United States, 33,000 people in the EU, and more than 30,000 in Asia. However, resistance is mainly acquired due to irrational antibiotic use (such as administering treatment for viral infections) and contamination from within hospitals. The contribution from aquaculture is unknown as of now, but given the high concentrations that persist in pens and wastewater, it is still important to limit the usage to decrease the chance of preventable treatment problems for human beings.

This issue is most prominent in countries where regulations are lax and antibiotic usage is abundant compared to countries such as the U.S. and Norway, which employ stricter measures on antibiotic usage.

Antibiotic Usage Today

There are two categories of antibiotics. Defined as “drugs of natural or synthetic origin that have the capacity to kill or to inhibit the growth of microorganisms and are non-toxic to the host, used in order to serve as treatment for disease”, antibiotics can be used to prevent disease (“prophylactic antibiotics) or to treat disease (“therapeutic antibiotics”). Troublingly, though, despite their use, limited data is available on the specific types and amounts of antibiotics required to control infection and disease.

While many uses have been banned, antibiotics of both forms are still used in some aquaculture settings today due to their effectiveness.

Antibiotics such as quinoles have been banned in the U.S. and Norway because of their use in human infection treatments, which is the major issue with administering antibiotics to fish and livestock in the first place. Still, major fish farming countries such as Chile and China, have actually increased their usage of quinole, though the National Fisheries Service of Chile recently proposed a monitoring program to address this problem.

In the U.S., the use of antibiotics in aquaculture is heavily restrictive: they must be FDA approved, may only be used for treatment, and all antibiotics that are used to treat human infections in any capacity are strictly banned. These restrictions extend internationally among countries that are in favor of eliminating any prophylaxis or treatments that are currently used for human medicine. On top of antibiotic-resistant bacteria concerns, a move towards prevention and health management instead of treatment, as well as vaccines and probiotics as emerging preventative practices, is forthcoming.

Caption: Major decline in antibiotic use after 2002, as well as with probiotics, chemicals, and vitamins; minerals and fertilizers have increased. There have been no newly approved antibiotics in US aquaculture since 2004. (https://www.aquacultureal… — Caption: Major decline in antibiotic use after 2002, as well as with probiotics, chemicals, and vitamins; minerals and fertilizers have increased. There have been no newly approved antibiotics in US aquaculture since 2004. (https://www.aquaculturealliance.org/wp-content/uploads/2016/08/Day1_HughMitchell_GOAL2015-copy.pdf).

There are only thirteen approved drugs for use in aquaculture in the United States, of which only six are true antibiotics. These include:

Fish Farmer Reactions to Antibiotic Restrictions

Farmers have traditionally been in favor of antibiotic use in aquaculture because it prevents large-scale die-offs and fish losses. However, there is promising data showing that fish farmers across the world are not only accepting of limited antibiotic usage but embracing the new reality.

In Asia, a research team led by Dr. Kelly Thornber assessed the feasibility of disseminating materials about the World Health Organisation’s global antimicrobial resistance (AMR) action plan. The materials were rolled out to a large audience across Bangladesh, where aquaculture is a major food production source - and where there is also an extensive 4G internet network and the majority of the population has mobile internet access. After the initial rollout, thirty-six farmers were surveyed, and 97% said it would change the way they use antibiotics in the future. Another, smaller group of a little over 30 aquaculture farmers in the southern Indian province of Kerala discussed the use of antibiotics in farming. They met at a one-day workshop organized by ReAct Asia, and every one of the farmers agreed and pledged to follow the “10 Commandments of Appropriate Antibiotics Use” with no issues or pushback against the restrictions put in place.

In Norway, a country where fish farming dominates the local and export food markets, farmers were also eager to cut antibiotics, though much sooner than most areas of the world. In 1994, Norwegian fish farmers began vaccinating fish in an effort to move away from using treatment and prophylaxis drugs to stop furunculosis and vibriosis in aquaculture farms. They adopted other methods as well, such as periodic holding area cleaning, and the result has been incredible. According to Dr Paul Midtlyng, a Norwegian veterinarian and former officer for fish health in the Norwegian Ministry of Agriculture during the days of heavy antibiotic usage: “Today, Norway has the largest tonnage of farmed salmon in the world and probably the lowest use of antibiotics.”

In Chile, the move away from antibiotics in aquaculture had been slow, but recently has gained traction. Improved early detection, new health management strategies, better use of vaccines and other methods to prevent diseases before they take hold have all been implemented. It has resulted in a total decrease of antibiotic usage by nearly half over the past five years. Farmers are not only on board with this reduction, they are one of the main catalysts.

Managing Water Quality and Disease without Antibiotics

(Source: ResearchGate [https://www.researchgate.net/figure/List-of-drugs-banned-for-use-in-aquaculture_tbl1_286914746])

While antibiotic-free organic fish farming is the future, the reality is that the same water quality, fish farm waste, and disease challenges exist that required antibiotics before. Therefore, it is imperative that there are effective, safe, and cost-competitive alternatives available in place of antibiotic treatments.

Vaccinations, functional diet changes, and early detection systems are helpful, but there is another type of treatment that holds a great deal of promise in safe prophylaxis of fish farming populations.

Probiotics offer a natural alternative to antibiotics

Probiotics used in farming pens and in aquaculture wastewater treatment may be the best bet for truly sustainable aquaculture - as well as truly organic fish farming with zero reliance and antibiotics or other more potentially harmful treatments such as aquatic pesticides.

The exact definition of probiotics has changed over the years, from a “live microbial food supplement that benefits the host (human or animal) by improving the microbial balance of the body” in early-stage usage to “microbial cells administered in a certain way, which reaches the gastrointestinal tract and remain alive with the aim of improving health” in recent years. The first application of probiotics in aquaculture occurred in 1986, where they were administered in an attempt to improve water quality and limit bacterial infections. Today, there are several commercial aquaculture-specific probiotics available to treat a variety of issues.

Probiotics differ greatly from antibiotics as they are themselves living bacteria - though they are harmless bacteria that help the wellbeing of the host and contribute, directly or indirectly, to protect against harmful bacterial pathogens. These helpful microorganisms improve feed value, and work by enabling an enzymatic contribution to digestion in fish (the same process as within humans), which leads to inhibition of pathogenic microorganisms, anti-mutagenic and anti-carcinogenic activity, and increased immune response. This promotes sustained growth, stimulated by improved digestion, and improved water quality overall. Probiotics prepare fish to fight against various pathogens, with (albeit limited) studies showing this treatment to have positive effects on fighting bacterial infections - as well as having antifungal and antiviral properties.

The use of probiotics in aquaculture is relatively new. This is due in large part to the fact that gastrointestinal microbiota of aquatic organisms is not fully understood and their effects have not been studied extensively. However, with the growing concern to find safe and sustainable alternatives in the treatment of water-borne diseases in aquaculture, the use of probiotics is a promising approach.

Given that the use of probiotics in aquaculture is a relatively recent development, its efficacy in fish-farming environments has not been widely studied as of yet. However, research into the use of probiotics for aquaculture is steadily increasing in tandem with the demand for more sustainable aquaculture.

On the path toward sustainable aquaculture

A few things are clear when it comes to the future of aquaculture:

The importance of aquaculture as a food source will only increase
Disease mitigation will always be a challenge to be dealt with
Antibiotics are effective, but overuse can result in lessening effectiveness and potentially causing harm to the human population
Probiotics afford disease mitigation benefits with the added benefit of being more ecological-friendly than other chemicals and safer than antibiotics

With the implementation of strict regulations, guidelines, and effective enforcement, the development of a more sustainable oceanic and sustainable freshwater aquaculture is possible.

At QB Labs, we’ve developed a comprehensive set of probiotics - tailored to the aquatic species and the use case. Whether you’re looking to control shrimp pond water, protect your hatchery, or cut out the fish farm waste and sludge accumulation in your pond, we have the high-impact, cost-effective solution for you. Even if you’re just getting started with probiotics, our team would love to chat with you!

In tandem with a comprehensive sustainable aquaculture plan, we can further decrease antibiotic use and chart a healthier, more sustainable, and more profitable future for aquaculture.