November 17, 2023


Research finds sea lice treatments linked to increased bacterial infection risk for salmon



In a recent study conducted by the Norwegian Veterinary Institute, certain sea lice treatments have been associated with an elevated risk of bacterial infection in salmon, Fish Farmer reported.


The research found that both thermal and non-thermal exfoliation methods, such as brushing or rinsing, can heighten the likelihood of the disease pasteurellosis.


Pasteurellosis in salmon manifests symptoms like skin boils, particularly around the pectoral fin and internal organs, resulting from infection by the bacterium Pasteurella. This disease has become a growing concern in recent times, ranking as the 10th major biological problem faced by salmon farmers.


Project director Duncan Colquhoun underscores that while pasteurellosis is not highly contagious or pathogenic, the correlation between lice treatments and the detection of Pasteurella implies that external factors, such as stress, may influence bacterial spread and disease development.


The study, incorporating de-licing data from the Fish Health Report, the Veterinary Institute's diagnostic data from 2018 to 2022, and diagnostic data from private laboratories between 2021 and 2022, analysed the potential impact of different de-licing methods on bacterial infection rates.


Results indicated a substantial increase in the odds of detecting Pasteurella in the month following thermal de-licing (177%) and brushing or rinsing (164%), whereas treatment with freshwater showed a modest 17% increase, which the Institute deems statistically insignificant.


Senior researcher Leif Christian Stige said the correlations do not necessarily reflect causation, highlighting the preliminary nature of the results, subject to verification with additional data.


-      Fish Farmer