Using ozone nanobubbles to mitigate the risk of mycobacteriosis in Siamese fighting fish (Betta splendens)

Abstract

Betta splendens, a valuable ornamental fish species, is particularly susceptible to mycobacteriosis which poses a challenge to the sustainability of its culture and trade. Since there are no effective treatments for the disease, betta fish farms must take rigorous preventive measures. This study investigated the efficacy of ozone nanobubbles (NB-O3) to disinfect water for mitigating the risk of mycobacteriosis in betta fish. Laboratory tests showed a significant disinfecting effect of NB-O3 against a highly pathogenic, multidrug-resistant strain of Mycobacterium chelonae by destroying bacterial cells. After incubation in NB-O3 water for 60 min, the concentration of M. chelonae in distilled water was reduced by 96.71 to 99.92%. In practice, treatment of reserved and cultured water from betta farms with direct NB-O3 for a single 10 min significantly reduced total bacterial counts and presumptive mycobacteria by over 90%. In experimental infection, sub-adult betta fish (2-month-old) cultured for 14 days in water spiked with M. chelonae (∼106 CFU/mL), which served as a positive control group, had a low percent survival of 38.33%. In contrast, fish reared in the same water as the positive control group but treated with NB-O3 three times for 10 min at 20 min intervals had a significantly higher percent survival of 93.93%. Moreover, the relative percent survival (RPS) of the treatment group showed a statistically significant difference, with an RPS of 89.19% compared to only 67.57% in the negative control group (neither exposure to M. chelonae nor treatment with NB-O3). In conclusion, this study demonstrated that NB-O3 effectively reduces bacterial concentrations in water, mitigates the risk of mycobacteriosis, and enhances the survivability of betta fish exposed to multidrug-resistant M. chelonae. This non-chemical and non-antibiotic approach offers a promising solution for disease control in the betta fish industry.