Virulent Aeromonas hydrophila (vAh) has been identified as the main pathogen in recent occurrences of motile Aeromonas septicemia (MAS) in commercial-sized channel catfish (Ictalurus punctatus) and hybrid catfish (Ictalurus punctatus X I. furcatus). In 2021, 2.05 million pounds of catfish were lost to vAh in West Alabama alone and at current live fish prices the estimated monetary loss is roughly US $2.6 million annually. Field r eports suggest that mortality is often observed after feeding or seining catfish. Therefore, u sing an existing bath immersion infection challenge model with fin clipping, we investigated the effects of skin integrity (fin-clipping) and dietary status (feeding) on c hannel catfish infected with vAh.
A total of 425 channel catfish (mean weight = 30g) were challenged with vAh strain, ALG-15-097, at a concentration of 1.5×107 CFU/mL in 4 treatment groups. Group 1 was fin clipped and fed (FCF, n=100), group 2 was not fin clipped but fed (NCF, n=100), group 3 was fin clipped but not fed (FCN, n=100), and group 4 was not fin clipped and not fed (NCN, n=100) . The fed groups that were fed 2 h prior to the challenge on commercial diet at 3% of the ir average body weight . All fish were anesthetized (MS-222 at 150mg/L), fin clipped treatments had their adipose fin cut off with scissors before being placed in flow-through tanks. N o fin clipped fish were placed in the tanks after anesthesia. The mortalities were recorded at 0, 1, 2, 4, 6, 8, 12, 20, 24, 36, 48 and 72 h ours. The control group (n=25) were manipulated like groups 1 (FCF) and 2 (NCF) but were mock challenged with sterile tryptic soy broth.
After 72 h post challenge, we observed 30%, 38%, 23% and 55% survival rate in groups 1 (FCF), 2 (NCF), 3 (FCN) and 4 (NCN) respectively. Overall, statistically significant differences were observed between treatments, except between groups 2 (NCF) and 4 (NCN) (Fig. 1). Results suggest skin integrity and dietary status are important factors in MAS pathogenesis.