Epidemiology and economic impact of disease-related losses on commercial catfish farms: A seven-year case study from Alabama, USA

The objectives of this study were to determine statewide production losses caused by diseases, identify the most incident catfish diseases affecting Alabama (AL) farm-raised catfish production in freshwater ponds and their annual pattern, and determine disease-related economic impacts. The Alabama Fish Farming Center (AFFC) conducted seven annual retrospective questionnaire surveys of AL catfish farmers since 2015 to assess the epidemiological situation of farm-raised catfish fish diseases and their economic impacts. Across the study (2015–2021), the annual number of survey respondents ranged from 64 to 74, with a total of 482 respondents. The yearly survey response rate ranged from 95.6 to 100% (mean: 98.2%). The annual survey coverage area ranged from 6410 to 7006 ha/year. About 97% of survey coverage area reported fish losses caused by a disease. Fish diseases resulted in the loss of 9 million fish/year (2.9 million kg/year; 436.7 kg/ha/year). Bacterial diseases resulted in >83% of catfish disease losses (>5 times losses to non-bacterial causes). The most incident statewide catfish disease was hypervirulent Aeromonas hydrophila (225 kg/ha/year), followed by columnaris (140 kg/ha/year), followed by Edwardsiella (52 kg/ha/year). The temporal epidemiological analysis results indicate that annual trends of proliferative gill disease and Bolbophorus disease were correlated with prolonged precipitation periods and total quantity of rainfall, respectively. Economic losses caused by fish losses to bacterial diseases, non-bacterial diseases, production losses due to reduced feeding during outbreaks, and expenditures associated with catfish diseases were responsible for 54.5%, 10.8%, 22.0%, and 12.7% of total direct economic impacts attributed to AL farm-raised catfish industry, respectively. Total disease-related financial losses in west AL were 11.1 million USD/year (1651 USD/ha/year), representing about 9.5% of food-size catfish sales in AL. The present study provides the first extensive assessment of epidemiology and health economics of farm-raised catfish disease in the freshwater pond environment for a substantial duration. More studies focusing on disease losses at the county- and farm-level would provide useful information regarding the spatial epidemiology of diseases and their underlying risk factors.