Effect of spatio-temporal variables, host fish species and on-farm biosecurity measures on the prevalence of potentially pathogenic Aeromonas species in freshwater fish farms

Abstract

Aims To determine the prevalence of Aeromonas species in freshwater fish farms, factors affecting their prevalence and virulence factors associated with each species. Methods and Results In a cross‐sectional study from 128 farms in four districts of Uttar Pradesh, India, 11 species of Aeromonas were identified by gyrB sequencing including the first report of Aeromonas crassostreae from fish. Four species of Aeromonas were more prevalent (MP) in fish farms, A. veronii bv. sobria (50.0%) was the highest, followed by A. caviae (18.8%), A. veronii bv. veronii (11.7%) and A. dhakensis (7.0%). The less prevalent (LP) species were A. hydrophila, A. media, A. jandaei, A. allosaccharophila, A. salmonicida, A. crassostreae and A. taiwanensis. Spatial variation in the prevalence of Aeromonas species was observed. Dominance of biovar sobria ranged from 33.3 to 68.6%, notably lesser in farms with on‐farm biosecurity measures. The prevalence of biovar veronii was significantly associated with pangas fish, rainy season and farms with on‐farm biosecurity measures. The prevalence of LP species was significantly higher in mrigal fish and winter season. Multiple virulence factors (>6) were detected in 70.2% of the Aeromonas species. Significant association of β‐hemolysin, DNase, slime production, act, ahh1, aexT and lip was observed with different species of Aeromonas. Moreover, 75.8% of Aeromonas species possessed one or more enterotoxins genes (act/alt/ast). Conclusion Significant association of spatio‐temporal variables, host fish species and on‐farm biosecurity measures were observed on the prevalence of some of the Aeromonas species in freshwater fish farms. Most of the Aeromonas species harboured virulence factors indicating their potential for pathogenicity. Significance and Impact of the Study This is the first study that determined the prevalence and identified the factors that affect the prevalence of Aeromonas species in freshwater fish farms. This information will be useful in managing Aeromonas infection in fish and their risks to public health.

Antibacterial activity of palmarosa oil significantly varies between Aeromonas veronii and Aeromonas caviae and exhibits selective action on tetracycline and sulfonamide resistant A. caviae

“…In this study, three EOs of plant origin were investigated for their antibacterial activity with an aim to control infections caused by A. veronii and A. caviae , especially by tetracycline and sulfonamide resistant strains. The farm prevalence of these two Aeromonas species is high in freshwater aquaculture ponds (Kumar et al, 2022). These pathogens may harbour AMR against frequently/commonly used aquaculture antimicrobials.…”

“…Thirty strains of Aeromonas species comprising A. veronii ( n = 18) and A. caviae ( n = 12) obtained from Fish Health Management and Exotic division, ICAR‐NBFGR, Lucknow were used in this study. All the strains were identified by gyrB sequencing (Kumar et al, 2022) and tested for antimicrobial susceptibility (AST) by disk diffusion method (Bauer et al, 1966) for tetracycline (30 μg) and sulfonamide class, trimethoprim–sulfamethoxazole (1.25/23.75 μg) using CLSI suggested breakpoints (CLSI, 2005). The AST categorization of these strains were tetracycline resistant ( n = 11), sulfonamide resistant ( n = 9) and susceptible to both antimicrobials ( n = 10).…”

“…Bacterial diseases are one of the major challenges with intensifying aquaculture (Pridgeon and Klesius, 2013). Among the most common bacterial fish pathogens are Aeromonas species, wherein Aeromonas veronii and Aeromonas caviae are more prevalent in the fish farms of Asia (Hoai et al, 2019; Kumar et al, 2022; Dhanapala et al, 2021). Furthermore, Aeromonas is an emerging food‐borne zoonotic pathogen associated with human diseases.…”

Aeromonas dhakensis: A Zoonotic Bacterium of Increasing Importance in Aquaculture

“…The aerolysin toxin is probably the most well-known and best-characterised cytotoxin of A. dhakensis and A. hydrophila, and this virulence factor, in addition to the ahh1 haemolysin, assists in overwhelming the host immune defences [1,[119][120][121]. The virulence capabilities of A. dhakensis isolates from fish hosts has been largely limited to screening for the presence or absence of predicted virulence genes [86,87,122,123], although challenge models have been established for several aquatic organisms (Table 4). Fortuitously, studies conducted with 'A.…”

“…Like many other infectious diseases in fish, the prevention of MAS relies on appropriate health management of stocks, which includes good husbandry, the avoidance of stress such as that caused by overcrowding and handling, and adherence to the key principles of biosecurity [13,117,123]. In certain circumstances, vaccination against Aeromonas spp., including A. dhakensis, can be a suitable approach to protect against these pathogens [133].…”