A Review of Bacterial Co-Infections in Farmed Catfish: Components, Diagnostics, and Treatment Directions

SIMPLE SUMMARY: Catfish aquaculture is a prominent agricultural sector for foodfish production in the Southern United States. Catfish producers often experience high-level mortality events due to bacterial pathogens. In many instances, co-infections caused by multiple bacterial fish pathogens are isolated during diagnostic cases. These bacterial–bacterial interactions may alter the infection dynamics, and many of these mechanisms and interactions remain unclear. Furthermore, these co-infections may complicate disease management plans and treatment strategies. The current review provides an overview of the prevalent bacterial pathogens in catfish culture and previously reported instances of co-infections in catfish and other production fish species. ABSTRACT: Catfish production is a major aquaculture industry in the United States and is the largest sector of food fish production. As producers aim to optimize production yields, diseases caused by bacterial pathogens are responsible for high pond mortality rates and economic losses. The major bacterial pathogens responsible are Edwardsiella ictaluri, Aeromonas spp., and Flavobacterium columnare. Given the outdoor pond culture environments and ubiquitous nature of these aquatic pathogens, there have been many reports of co-infective bacterial infections within this aquaculture sector. Co-infections may be responsible for altering disease infection mechanics, increasing mortality rates, and creating difficulties for disease management plans. Furthermore, proper diagnoses of primary and secondary pathogens are essential in ensuring the correct treatment approaches for antimicrobials and chemical applications. A thorough understanding of the interactions and infectivity dynamics for these warm water bacterial pathogens will allow for the adoption of new prevention and control methods, particularly in vaccine development. This review aims to provide an overview of co-infective pathogens in catfish culture and present diagnostic case data from Mississippi and Alabama to define prevalence for these multiple-species infections better.