Vibriosis is one of the most common diseases in mariculture, caused by bacteria of the Vibrio genus, which affects many economically important aquaculture species worldwide.
Vibrio species are linked to infections in fish that cause symptoms such as skin ulceration, scale loss, and necrosis of the caudal fin.
The use of antibiotics is the most employed method to treat vibriosis in aquaculture. However, the uncontrolled use of antibiotics has led to the emergence of antibiotic-resistant bacterial strains, limiting the effectiveness of treatment.
In this regard, a team of researchers from Universiti Putra Malaysia published a scientific review of studies on vibriosis, specifically focusing on its treatments and limitations, as well as the application of nanoparticles in aquaculture.
Here is a summary of the study, and you can access the full publication at the end of this article.
Vibriosis
Vibrio spp. are Gram-negative bacteria that cause vibriosis. Vibriosis is a waterborne infection, meaning that the causal agent spreads through the water column. Vibrio species inhabit a variety of aquatic habitats, including rivers, estuaries, seas, and deep ocean waters.
Vibrio species are known to be opportunistic pathogens, meaning they cause diseases when the host’s immune system is suppressed or weakened due to physiological or environmental factors present in aquaculture systems.
Treatments against Vibriosis
Antibiotics
Antibiotics are the most common treatment used in aquaculture to treat bacterial infections, and most Vibrio spp. are susceptible to them. Antibiotics are widely used in bath treatments or mixed with food for therapeutic use.
Antibiotics like oxytetracycline, tetracycline, quinolones, nitrofurans, potentiated sulfonamides, trimethoprim, sarafloxacin, flumequine, and oxolinic acid have been used to treat vibriosis.
However, antibiotic resistance has developed in pathogens due to widespread and frequent antibiotic use in aquaculture in the past. The emergence of resistant bacteria and resistant genes can impact treatment effectiveness and public health by spreading antibiotic-resistant bacteria to consumers.
Vaccination
Techniques are being researched to combat vibriosis, including vaccines for prevention and control of vibriosis in aquaculture, with promising results.
A vaccine is a non-harmful biological agent that provides increased immune protection by inducing targeted and long-lasting immunological memory.
Vaccine administration can trigger an immune response in the recipients’ bodies. Targeted antibodies can neutralize and eradicate pathogenic microbes and toxins they produce, providing superior protection against pathogenic microorganisms.
Vaccination is a safer and more effective way than antibiotics to prevent and control vibriosis in aquaculture. Vaccination not only reduces antibiotic use but can also trigger a robust immune response. However, inactivated vaccines have disadvantages of high inoculation dosage, short immunization time, and a single immunization route, requiring multiple immunizations.
Despite the positive effects of vaccines, there is a debate about the suitability of vaccine use in invertebrates due to their lack of specific and adaptive immune systems.
Probiotics
Probiotics are microbial compounds that can be administered to fish in the form of food supplements or water to enhance disease resistance, health, growth performance, and stress response modulation.
Bacillus, Lactococcus, Lactobacillus, Pseudomonas, Enterococcus, Aeromonas, Alteromonas, Bifidobacterium, Clostridium, Phaeobacter, Pseudoalteromonas, Rhodosporidium, Roseobacter, Streptomyces, and several other bacterial species have been shown to be effective in aquaculture feeding with unique beneficial properties.
Although probiotics have many advantages, they also have limitations. The most significant disadvantage of using probiotics is that they often cannot sustain themselves and require regular supplementation, making this strategy less cost-effective. Additionally, the specificity and longevity of probiotics for protection are uncertain.
Phytotherapy
Phytotherapy has remained a key area of research in the quest for safer, more precise, and reliable treatments. The aquaculture industry favors phytotherapy as it is affordable and environmentally friendly.
Previous studies have shown that medicinal plants exhibit strong antibacterial activity against Vibrio spp. The antimicrobial activity of plant extracts is known to correlate with their active compounds found in various parts of the plant, such as roots, leaves, fruits, seeds, and skin.
Several parts of medicinal plants have demonstrated antibacterial effects; however, most studies on the potential benefits of these substances have focused solely on in vitro experiments. Bioactive natural compounds are essential components of medicinal plant extracts, but their mechanisms of action are still unclear.
Nanoparticles in Aquaculture
Nanotechnology is one of the fastest-growing innovations in recent years. Nanoparticles are small materials ranging from 1 to 100 nm in size, which exhibit a high surface-to-volume ratio, a characteristic that makes them suitable for various applications, such as biomedical, drug delivery, optics, and electronics.
Recently, it has been reported that nanoparticles have the potential to prevent microbial growth, and their efficiency in reducing most bacterial infections has been demonstrated.
Graphene Oxide Nanoparticles
Graphene oxide is one of the promising nanoparticles that has been used in biological applications such as biosensors, drug delivery, and potential treatment for infectious diseases.
Researchers report that graphene oxide has demonstrated antibacterial properties against both Gram-positive and Gram-negative bacteria, but no research emphasizing its impact on Vibrio spp. has been published.
Conclusions
Researchers highlight that nanoparticles have been used in a variety of biological applications, including antibacterial agents, and there is the potential to use nanoparticles to control diseases in aquatic organisms.
“As a carbon-based material, graphene oxide has been used in a wide range of applications due to its unique characteristics. Graphene oxide has antibacterial properties that can inhibit a wide range of microorganisms. The application of graphene oxide in aquaculture is still under consideration due to its toxicity at higher concentrations and a lack of studies on its effect in the aquatic environment,” they concluded.
The study was funded by the Ministry of Higher Education, Malaysia, under the Fundamental Grant Research Scheme (FRGS).
Reference (open access)
Kah Sem, N.A.D.; Abd Gani, S.; Chong, C.M.; Natrah, I.; Shamsi, S. Management and Mitigation of Vibriosis in Aquaculture: Nanoparticles as Promising Alternatives. Int. J. Mol. Sci. 2023, 24, 12542. https://doi.org/10.3390/ijms241612542
