Aquaculture Canada and WAS North America 2022

August 15 - 18, 2022

St Johns, Newfoundland, Canada

CO-INFECTION OF LUMPFISH WITH Aeromonas salmonicida ANDVibrio anguillarum

Chukwu-Osazuwa Joy*, Trung Cao, Ignacio Vasquez, Hajarooba Gnanagobal, Ahmed Hossain, Javier Santander

Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Memorial University of Newfoundland, St. John’s, NL, *Correspondence: ; Tel.: 1-709-8643268


Co-infection is a major challenge affecting aquaculture globally. Marine finfish have high tendencies to be affected by more than one pathogen concurrently in nature. Unfortunately, not enough attention is given to the studies of coinfection in aquaculture. Many commercial vaccines are developed to prevent single infection with little or no effort made towards the development of vaccines to combat co-infection. This can be because there is a lack of information on the infection patterns of different pathogens in several fish species. The susceptibility of fish to different pathogens or the severity of an infection caused by a pathogen can be alter during co-infections. There is need to understand how various pathogens affect fish in the presence of another pathogen. In this study, we investigated the co-infection of Lumpfish (Cyclopterus lumpus), a sea-lice biocleaner fish used in Atlantic salmon (Salmo salar) aquaculture with frequent marine bacterial pathogens Aeromonas salmonicida and Vibrio anguillarum. Three groups of fish were intraperitoneally injected with either PBS (control group) or sub-lethal doses of 101 and 104 or 102 and 105 CFU/ml of A. salmonicida and V. anguillarum, respectively. This experiment was conducted in duplicates and results showed regular clinical signs including petechial hemorrhage, skin lesions and exophthalmos. Survival rate ranged from 0 to 30%. Bacterial colonization revealed that sub-lethal doses of A. salmonicida could not be recovered on Tryptic Soy Agar (TSA) plates supplemented with the appropriate antibiotic marker because of the low doses. This was further elucidated in an in-vitro sea water analysis using 105 and 105 CFU/ml A. salmonicida and V. anguillarum respectively. The co-infection of lumpfish with A. salmonicida and V. anguillarum may be responsible for the increased mortality and severe clinical sign observed in this experiment even at sub-lethal doses suggesting a synergistic interaction between these bacteria.

Keyword: Petechial hemorrhage, skin lesions, exophthalmos, synergistic