Aquaculture facilities, while efficient, create ideal conditions for pathogens to thrive. Rising water temperatures, driven by climate change, further exacerbate the problem, expanding the scope and potency of microscopic threats. Mollusks, such as oysters and mussels, are particularly vulnerable to diseases despite their role as filter feeders, which improves the quality of local water.
In this context, scientists from the University of California and the University of Memphis published a scientific review highlighting the primary microbial threats to mollusk aquaculture and current and alternative solutions, considering the accessibility of the proposed solutions.
Microbial threats to mollusk aquaculture
Mollusks can be infected by a broad group of bacterial, viral, and protist pathogens that can lead to massive mortality events and may even accumulate in mollusk tissues, posing a risk to human consumption.
“As filter feeders and herbivores, mollusks are continually exposed to new microbes and potential pathogens from their environment,” report the scientists, indicating that mollusk-associated microbiomes are host and tissue-specific.
When a mollusk is stressed, it is more likely that the microbiome shifts to an altered state, sometimes called dysbiotic. In this state, it is more prone to diseases.
As detailed in the study, microbes affecting mollusks also pose a risk to consumers. Vibrio species lead the causes of bacterial infections related to the consumption of fish and seafood, resulting in gastroenteritis, vomiting, diarrhea, and, in some cases, death.
Solutions to mitigate microbial threats
Many solutions have been implemented to confront or minimize microbial threats in mollusk aquaculture. The study authors highlight the following:
- Hatchery: Pathogen control primarily involves the use of mechanical filters to prevent the entry of pathogens into the aquaculture farm. Filtration with sand filters, sterilization with ultraviolet light, and ozonation are also used to reduce or remove external contaminants from the water entering the hatchery.
- Larval settlement and seeding: There are limited options for aquaculture producers. Because mollusks lack an adaptive immune system, they are not good candidates for vaccine development, so antibiotic therapy is one of the most viable options to control disease spread.
- Harvest and processing: The main concern is to control pathogens that can affect humans. Many operations employ control measures before or immediately after harvest, such as rapid cooling, to prevent potential pathogen growth. Some operations use methods to further minimize pathogen loads, such as depuration, before sale.
How to use microbes?
Microbes also have the potential to benefit mollusk aquaculture through pathogen biocontrol, and animal resistance and growth can be improved.
- Probiotics: Beneficial microorganisms that help increase resistance in the host, surpassing harmful pathogens, and stimulating the immune system of cultivated mollusks.
- Phage therapy: Imagine microscopic submarines programmed to attack and destroy specific pathogens. That is the promise of phage therapy, which uses natural viruses to eliminate bacteria-causing diseases.
Microbes as “tools” in aquaculture
The study proposes sustainable solutions focusing on using microbes to improve production and prevent disease outbreaks. Beyond these cutting-edge solutions, a holistic approach is crucial and should include:
- Early detection and monitoring: Close monitoring of microbial activity in coastal waters and mollusk populations allows for rapid intervention and outbreak prevention.
- Sustainable practices: Reducing dependence on antibiotics and promoting responsible aquaculture methods minimizes the emergence of resistant pathogens.
- Collaboration is crucial: From mollusk producers and government regulators to industry experts and indigenous communities, a united front is vital to safeguard our seafood supply.
By adopting these strategies, we can ensure a sustainable future for mollusk aquaculture.
Scientists conclude that there is a significant opportunity for advances in aquaculture technology to strengthen the sustainable expansion of the mollusk farming industry.
“Probiotics and phage therapy (as alternatives to antibiotics) are promising for mitigating the impact of diseases and have the additional benefit of improving yields,” they concluded.
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Reference (open access)
Emily Kunselman, Kara Wiggin, Rachel E Diner, Jack A Gilbert, Sarah M Allard, Microbial threats and sustainable solutions for molluscan aquaculture, Sustainable Microbiology, 2024;, qvae002,