天美传媒

Herbal medicine; Aeromonas hydrophila; Fish disease control; Antibacterial activity; Aquaculture biosecurity; Medicinal plants; Phytotherapy; Freshwater aquaculture; Natural immunostimulants; Antibiotic alternatives

Introduction

Freshwater aquaculture has become a vital source of animal protein in many developing countries, yet it is highly susceptible to bacterial infections that compromise fish health and yield. Among these, Aeromonas hydrophila is a major opportunistic pathogen responsible for motile Aeromonas septicemia (MAS), leading to high mortality rates and economic losses, especially in carp and catfish species [1-5]. Conventionally, antibiotics have been used to control such infections, but the rising concern over antibiotic resistance, drug residues in aquatic products, and environmental pollution has prompted a shift toward alternative, eco-friendly disease management strategies. Herbal extracts, rich in antimicrobial phytochemicals such as flavonoids, tannins, and alkaloids, offer a promising natural alternative. This study evaluates the efficacy of selected herbal extracts in controlling A. hydrophila infections in freshwater aquaculture, focusing on their antibacterial activity, safety, and immunomodulatory potential [6-10].

Discussion

The experiment was conducted using healthy specimens of rohu (Labeo rohita) maintained in controlled freshwater tanks. Four locally available medicinal plants—Azadirachta indica (neem), Ocimum sanctum (tulsi), Curcuma longa (turmeric), and Allium sativum (garlic)—were selected based on ethnoveterinary use and literature evidence. Ethanolic and aqueous extracts were prepared using Soxhlet extraction and tested in vitro for antibacterial activity against A. hydrophila using the agar well diffusion method.

Among the tested herbs, garlic and neem extracts exhibited the highest zones of inhibition (19.4 mm and 18.2 mm respectively), followed by tulsi (16.5 mm) and turmeric (14.7 mm), indicating strong antibacterial potential. The minimum inhibitory concentration (MIC) values ranged from 50 to 100 µg/mL, confirming bacteriostatic effects at low concentrations.

To assess in vivo efficacy, fish were divided into five groups: control (no infection), infected untreated, and three infected treatment groups receiving garlic, neem, and tulsi extracts mixed in feed (1% w/w) for 14 days post-infection. The herbal-treated groups showed significantly reduced mortality and clinical symptoms, with the garlic-treated group achieving a survival rate of 90%, compared to 40% in the untreated infected group.

Additionally, treated fish showed improved hematological parameters, such as increased total leukocyte count and elevated lysozyme activity—indicative of enhanced innate immunity. Histopathological examination revealed reduced tissue damage in the liver and kidneys of treated fish, supporting the therapeutic effects of the extracts.

Notably, the herbal treatments had no negative impact on feed intake or growth rate, and water quality remained stable throughout the trial, suggesting the plant extracts were safe and environmentally benign. These findings align with previous studies demonstrating the immunomodulatory and antibacterial effects of phytochemicals in fish, reinforcing the case for herbal therapies in aquaculture.

Conclusion

The study demonstrates that certain herbal extracts—particularly garlic and neem—can effectively control Aeromonas hydrophila infections in freshwater fish through their antibacterial and immunostimulatory properties. These extracts provide a natural, sustainable, and safe alternative to antibiotics in aquaculture, supporting both fish health and environmental integrity. Their incorporation into fish feed can be economically feasible, especially in regions with abundant access to medicinal plants. While results are promising, further studies on long-term application, standardization of dosages, and mechanisms of action are recommended. Integrating herbal remedies into aquaculture disease management could significantly reduce antibiotic dependency and promote more resilient aquaculture systems.

References

1. Besbes B (2009) . World's Poult Sci J 65: 260-271.

   , Crossref,

2. Aman G, Bangu B, Bereket Z (2017) . Int J Livest Prod 8: 145–157.

    

3. Nebiyu YA (2016) . Department of Animal Production Studies, College of Veterinary Medicine and Agriculture, Addis Ababa University.

4. FAOSTAT (2018) .

    

5. Delgado C, Rosegrant M, Steinfeld H, Ehui S, Courbois C (1999) . Food, Agriculture and Environment Discussion Paper 28.

   , Crossref,

6. Mack S, Hoffmann D, Otte J (2005) . World’s Poult Sci J 61: 7-14.

   ,

7. Alemu D, Degefe T, Ferede S, Nzietcheung S, Roy D (2008) .

8. Abdelqader A, Wolnny CBA, Gauly M (2007) . Trop Anim Health Prod 39: 155-164.

   , Crossref,

9. Solomon Z, Binyam K, Bilatu A, Ferede A (2013) . WJAR 2: 256-262.

   ,

10. Halima H (2007) . University of the Free State.