Brazilian aquaculture faces evolving threat from adaptable columnaris pathogens

New research reveals a broader and more adaptable set of columnaris bacteria affecting Brazil’s main farmed fish species, prompting calls for improved hygiene and targeted vaccines.

Brazil’s aquaculture sector is contending with a broader and more adaptable set of columnaris pathogens than previously recognised, according to research published in Microbial Pathogenesis. Scientists identified Flavobacterium species in fish samples taken from São Paulo, Minas Gerais and Paraná, extending the known reach of bacteria that had largely been associated with Asia and the United States.

The study found the organisms in farmed Nile tilapia, still Brazil’s main commercial species, as well as in native stocks including tambaqui, pacu, lambari and Amazon spotted catfish. That matters because columnaris disease attacks skin and gills, can spread quickly in warm water and is especially damaging to larvae and fry.

The researchers also reported species-level findings that widen the host range. One bacterium, Flavobacterium oreochromis, was detected in native food fish, while Flavobacterium davisii was recorded for the first time in Amazon spotted catfish.

Laboratory work suggested the pathogens are well suited to Brazilian conditions. Several grew best at 28C, while one performed even better at 35C. The bacteria also formed biofilms on surfaces, raising the risk of persistence on tanks, nets and equipment between outbreaks.

The authors say the findings support tighter hygiene controls, carefully calibrated salt use and the development of autogenous vaccines, possibly delivered by bath treatment for young fish.