One of the main concerns of fish farmers is maintaining the health of their fish to ensure a good harvest; however, stressful conditions in aquaculture facilities can create the perfect environment for the proliferation of infectious microorganisms.
The primary strategy employed by aquaculturists to maintain healthy populations of cultured aquatic organisms is the use of antimicrobials, which have negative impacts such as the development of antibiotic-resistant bacterial strains, and antibiotic abuse affects fish, the environment, and consumers.
Researchers from the Agriculture Research Center (ARC) evaluated the effects of using florfenicol with the microalga Spirulina platensis as additives in the diet of Nile tilapia (Oreochromis niloticus), on blood biochemical parameters, antioxidant status, immunity, and susceptibility; and whether spirulina enhances the efficacy of florfenicol treatment.
The Antibiotic Florfenicol
Florfenicol is a broad-spectrum, low-toxicity antimicrobial. In addition to chloramphenicol-like properties such as broad-spectrum activities against Gram + and – bacteria and rapid tissue penetration, florfenicol has an extended elimination half-life.
Florfenicol is widely used in the aquaculture industry to treat infections in various countries, including China, Brazil, the USA, Egypt, Norway, South Korea, and Vietnam.
It has been reported that florfenicol has antibacterial activity against common fish bacterial diseases, including Vibrio anguillarum, A. salmonicida, A. hydrophila, Flavobacterium psychrophilum, Yersinia ruckeri, and Edwardsiella ictaluri.
Despite all the benefits of florfenicol in aquaculture, negative effects have also been reported in fish, such as alterations in hematological markers, increased liver weight, and testicular degeneration in rats and dogs.
In tilapia, research reports indicate that florfenicol, after a 48-hour exposure, can cause oxidative stress, resulting in cellular oxidative damage. Thus, florfenicol can be toxic to fish species.
The researchers worked with two experimental groups, with the first group being fed the control diet, while the second group was fed a diet enriched with spirulina.
At the end of the feeding trial, the therapeutic efficacy of florfenicol and spirulina was evaluated through an experimental challenge of tilapia with a pathogenic strain of A. hydrophila.
Positive Effects of Spirulina
“In the current research, hematological parameters of O. niloticus were improved by Spirulina platensis, indicating that spirulina is a safe supplement for O. niloticus diets,” the scientists noted.
To assess whether spirulina combined with florfenicol could improve the antimicrobial’s side effects, researchers examined changes in some markers of liver and kidney damage and found that S. platensis modulated the florfenicol-induced increase in these markers.
“S. platensis did not show adverse impacts on the liver function of O. niloticus. Histopathological findings of the kidney and liver demonstrated its protective role,” they reported.
On the other hand, study results reveal that florfenicol feeding resulted in oxidative stress, expressed by elevated GPx, CAT, and SOD activities. “Again, spirulina inclusion restored the level of antioxidant enzymes to normal. This minimizes the severity of oxidative damage to the liver and kidney induced by florfenicol,” they highlighted.
Ultimately, irrespective of the immunosuppressive impacts of florfenicol, when combined with Spirulina platensis, the strongest immunological response and disease resistance were achieved. “This was evident in lower mortalities in challenged fish fed Spirulina + florfenicol, compared to fish fed separately.”
“Exposure to florfenicol resulted in oxidative damage in O. niloticus, but did not affect hematological parameters. Our findings indicate that even at therapeutic doses, florfenicol can be detrimental to Nile tilapia,” the researchers emphasize.
According to the study results, the combination of spirulina and florfenicol reduces oxidative stress and diminishes liver and kidney damage, as well as spleen tissue damage induced by florfenicol and/or bacterial infection.
“This trial promotes the use of alternative additives, such as immunostimulants (SP), in combination with an appropriate amount of antibiotics, to combat diseases and raises awareness about antibiotic overuse to reduce environmental risks and bacterial resistance,” they concluded.
Nagwa I.S. Abu-Zahra
Department of Fish Diseases,
Kafrelsheikh Provincial Lab, Animal Health Research Institute (AHRI)
Agriculture Research Center (ARC), Giza, Egypt
Reference (open access)
Abu-Zahra, N.I., Elseify, M.M., Atia, A.A. et al. Impacts of florfenicol on immunity, antioxidant activity, and histopathology of Oreochromis niloticus: a potential protective effect of dietary spirulina platensis. Vet Res Commun (2023). https://doi.org/10.1007/s11259-023-10189-9