By: Mahmoud A. O. Dawood, Mohammed F. El Basuini, Amr I. Zaineldin, Sevdan Yilmaz, Md. Tawheed Hasan, Ehsan Ahmadifar, Amel M. El Asely, Hany M. R. Abdel-Latif, Mahmoud Alagawany, Nermeen M. Abu-Elala, Hien Van Doan y Hani Sewilam.
Due to the increase of consumer demand, aquaculture technique has been shifted from extensive to super intensive. Intensification of aquaculture needs a higher amount of artificial feed supply, water treatment and reuse, and high stocking density resulting in aquatic environmental degradation.
Mounting of stress and quality deterioration of living environment increases the activity and virulence of infectious and opportunistic microbial pathogens. To eliminate diseases and parasitic attacks in the aquaculture industry, different synthetic antibiotics, chemical drugs, vaccines, and chemotherapeutics are being used at high rates from year after year.
Using of these chemical substances cause mass killing of beneficial aquatic bacteria, produce multi-drugs resistant pathogens, and leaving residues in fish which can be transmitted to human. Essential oils (EOs) are the secondary metabolites of medicinal plants and possess bioactive properties to be used as a phytotherapeutic agent for sustainable aquaculture.
Terpens, terpenoids, phenylpropenes, and isothiocyanates are the key chemical groups identified in EOs. EOs mainly penetrate and act upon the membrane and cytoplasm of bacteria to inhibit their action mechanisms by altering cell morphology and organelles deformities.
Although natural EOs have enough potential for sustainable aquaculture, EOs have high volatility and can be decomposed by exposure to heat, humidity, light, and oxygen to lose effectiveness. The use of nano encapsulated EOs becomes a promising trend in the field of EOs applications, especially in the aquaculture sectors, protecting the volatilization, low stability, low solubility in water, and associated problems of using EOs
The focus of this article is to identify EOs antimicrobial and antiparasitic properties that can be used for sustainable aquaculture practices. Moreover, EOs effects for aquaculture species growth, immunomodulation, and infection resistances were also postulated. In addition, research gaps and tentative future research activities are also mentioned to effectively use EOs in sustainable fish culture.
EOs as Growth, Immunity, and Disease Resistance Enhancer
Modulation of the intestinal microbiome by EOs can be considered one of the possible reasons for the modulation of immune-related genes. Significantly, phenolic compounds like thymol and carvacrol modulate innate immunity through two possible ways i) direct action on host tissue ii) influence on the intestinal microbial community. A 60-day experiment was conducted with dietary supplementation with bitter lemon (Citrus limon), and sweet orange peels (C. sinensis).
In both cases, EOs elevated innate immune parameters (NBT, WBCs, lysozyme, and myeloperoxidase activity) and decreased serum/blood glucose, cholesterol, and triglycerides. C. limon and C. sinensis EOs administrated tilapia demonstrated resistance against Streptococcus iniae and Edwardsiella tarda, respectively.
Essential Oils as Antiparasitic Agents Acanthocephalas Neoechinorhynchus buttnerae
Acanthocephalas Neoechino-rhynchus buttnerae is an acanthocephalan parasite causing significant economic losses in Colossoma macropomum fish in the region of Amazon.
It was reported that Mentha piperita, Lippia alba, and Zingiber officinale and Piper hispidinervum, Piper hispidum, Piper marginatum, and Piper callosum essential oils showed 100% anthelmintic effect on N. buttnerae.
Anacanthorus spathulatus, Notozothecium janauachensis, and Mymarothecium boegeri cause significant infections in species belonging to the Serrasalmidae family as C. macropomum fish being.
Among the EOs, the most effective one was Lippia sidoides. Dactylogyrus spp is one of the most common parasitic pathogens in cultured freshwater fish. When L. Origanoides and L. Sidoides EOs were applied as 100 mg/L for 5 min, they showed 100% efficacy. Cichlidogyrus is the parasite genus that occurs naturally in cichlid fish and has the most species among gill parasites, with its 131 different species known.
Lippia sidoides EO had 100% efficacy against Cichlidogyrus spp. and Scutogyrus longicornis when applied as 160 mg/L for 1 min 58 s while Mentha piperita EO had 100% efficacy when applied as 320 mg/L for 8 min 11 s. Dawestrema spp. Application of M. piperita EO as 160 and 320 mg/L for 30 min showed 100% efficacy on D. cycloancistrium and D. cycloancistrioides parasites. Gyrodactylus spp. causes economic losses in many cultured fish species. Only O. americanum EO as 50 mg/L for 1 h had the most effective anthelmintic action (98% efficacy) against Gyrodactylus spp.
Trepomonadea Hexamita inflata
Hexamita inflate is a flagellated anaerobic protozoan and free-living in fresh and seawater. Moon, et al. reported that L. angustifolia and L. intermedia EOs as 1 and 0.5% for 30 min exhibited 100% efficacy on H. inflate.
Clinostomidae Euclinostomum heterostomum
Euclinostomum heterostomum is parasitic trematodes and very common in Europe, Asia, and Africa. It infects muscular tissues and kidneys of freshwater fish. Verbesina alternifolia and Mentha piperita EOs could act on E. Heterostomum in high doses and for a long time.
Oligohymenophorea Ichthyophthirius multifiliis
Ichthyophthirius multifiliis is the most famous virulent ciliated protozoan ectoparasite that invades the skin, fins, and gills of fish. de Castro Nizio, et al. indicated that Varronia curassavica EO showed 100% efficacy against I. multifiliis trophont and tomont when applied as 10 mg/L and 50 mg/L for one h, respectively. EOs applications were also found to be effective on I. multifiliis.
Essential Oils as Antibacterial Agents: An In Vitro Perspective Aeromonas spp.
It is known that many different Aeromonas species cause disease in fish. The antimicrobial effects of Origanum onites, O. vulgare, and Thymbra spicata EOs on 18 different A. salmonicida isolates, and it was reported that EOs of these herbs formed 10 to 30 mm zone depending on the disc diffusion test, and they had moderate inhibitory depending on MIC values. Cinnamomum cassia EO was reported to have a very high inhibitory effect on A. salmonicida subsp. with a 56 mm zone diameter. T. vulgaris EO had the highest zone diameter on Aeromonas sobria and Aeromonas veronii with 31.5 mm and 36 mm, respectively.
Cymbopogon nardus and Syzygium aromaticum EOs had a strong inhibitory effect on Aeromonas hydrophila and Aeromonas spp. It was found that C. cassia, Cin- namomum aromaticum, Cymbopogon citratus, and Origanum vulgare EOs were effective against Aeromonas spp., Aeromonas salmonicida subsp. Salmonicida, A. hydrophila, and A. veronii bv. Sobria Among Piper aduncum, Piper callosum, Piper hispidinervum, Piper hispidum, and Piper marginatum EOs on 11 different A. hydrophila isolates, only P. marginatum had a strong inhibitory effect on three different A. hydrophila isolates It was reported that Eucalyptus globulus, Lavendula angustifolia, Origanum vulgare, and Melaleuca alternifolia nanoemulsions were more effective on A. hydrophila than their EOs, and among four different herbs, O. vulgare essential oil was found as the most effective Vibrio spp., Listonella anguillarum, and Photobacterium damselae Historically, vibrionaceae family members are the most severe infectious diseases in marine fish species.
The antimicrobial effects of O. vulgare, M. alternifolia, C. citratus, C. verum, and T. vulgaris EOs on Vibrio campbellii, Vibrio harveyi, Vibrio vulnificus, and Vibrio parahaemolyticus have been researched, and it was reported that generally moderate and weak inhibitory effects of these EOs on Vibrio spp. It was reported that E. globulus, L. angustifolia, O. vulgare, and M. alter nifolia nanoemulsions were more effective on Photobacterium damselae than their EOs, and among these herbs, O. vulgare EO and nano-emulsion were found as the most effective.
Pseudomonas fluorescens Pseudomonas fluorescens is a harmful pathogen in a variety of farmed fish. It was reported that Ocimum basilicum EO exhibited a potent inhibitory with 9 μL/mL MIC value on P. fluorescens, C. Nardus and S. aromaticum EOs showed marked activity on Pseudomonas spp. and P. Aeruginosa.
“The efficiency of EOs depends on plant variables, chemical compositions of bioactive compounds, environmental characteristics of plant origin, and parts of plants from which EOs is extracted.“
Citrobacter spp. Citrobacter spp. is an opportunistic fish pathogen affecting farmed fish species. It was determined that C. freundii showed susceptibility towards the Argania spinosa EO with a zone diameter of 15 mm.
Raoultella ornithinolytica Raoultella ornithinolytica was isolated from kidneys and skin lesions of naturally diseased silver catfish (Rhamdia quelen), and Ocimum gratissimum EO showed a moderate inhibitory effect on this pathogen.
Nocardia seriolae Nocardia seriolae is the causative agent of nocardiosis in cultured fish species. The most effective herb species were C. zeylanicum and T. vulgaris.
Flavobacterium spp. Flavobacterium species are widespread in soil habitats and fresh and marine waters and cause economic losses in cultured fish. T. vulgaris EO exhibited a potent inhibitory with 320 μg/ mL MIC value on F. psychrophilum.
Staphylococcus aureus Staphylococcus aureus is an important Gram-positive opportunistic pathogen for aquaculture species. Gulec, et al. reported that O. acutidens EO formed a zone diameter of 28 mm on S. aureus, Z. officinale, N. Sativa, T. Vulgaris, S. Aromaticum and E. Sativa EOs had no inhibitory effects on S. aureus.
Streptococcus spp., Lactococcus spp., and Vagococcus salmoninarum Streptococcaceae family species are important Gram-positive pathogens for cultured fish. Among L. alba, L. sidoides, M. piperita, O. gratissimum, and Z. officinale EOs, strong inhibitory effects of L. sidoides EO was reported on Streptococcus agalactia. Gholipourkanani, et al. determined that among E. globulus, L. angustifolia, O. vulgare, and M. alternifolia nano-emulsions and EOs, O. vulgare EO and/or nano-emulsion were found as the most effective on Streptococcus iniae.
A remarkable activity of Z. multiflora and R. officinalis EOs were reported, respectively, with 0.06 μL/ mL and 0.5 μL/mL MIC, and 0.12 μL/mL and 0.25 μL/mL MBC for S. iniae. Similarly, R. Officinalis, Z. Multiflora, A. Graveolens, and E. Globulus EOs exhib- ited potent inhibitory effects on S. iniae, and R. Officinalis showed the highest inhibition with a zone of 45 mm, and MIC value of 3.9 μg/mL, and MBC value of 7.8 μg/mL Zataria multifora, Thymbra spicata, Bunium persicum, Satureja bachtiarica, and Thymus daenensis EOs exhibited potent inhibitory effects.
Research Gaps and Concluding Remarks
The efficiency of EOs depends on plant variables, chemical compositions of bioactive compounds, environmental characteristics of plant origin, and parts of plants from which EOs is extracted. Sometimes plant originated EOs possess a mixture of different compounds, which may produce undesirable side effects on fish and shellfish. Commercial pharmaceutical companies might play significant roles in refining the desirable and undesirable compounds of EOs to achieve better effects in fish culture. Before applying EOs in aquaculture from any new plants, local and international drug regulating agencies (FDA or EU) permission or guidelines should be needed or followed.
This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “Antiparasitic and antibacterial functionality of essential oils: an alternative approach to sustainable aquaculture” developed by: Mahmoud A. O. Dawood, Mohammed F. El Basuini, Amr I. Zaineldin, Sevdan Yilmaz, Md. Tawheed Hasan, Ehsan Ahmadifar, Amel M. El Asely, Hany M. R. Abdel-Latif, Mahmoud Alagawany, Nermeen M. Abu-Elala, Hien Van Doan and Hani Sewilam. The original article was published on The original version was published in February 2021 via Pathogens.