Vaccines for the prevention of the two major diseases of catfish

Award Year 

A team from the ARS Mid South Area’s Aquatic Animal Health Research Unit demonstrated exceptional creativity in the invention and transfer of the first U.S. modified live vaccines that protect channel catfish from enteric septice-mia and columnaris. Enteric septice-mia and columnaris are the two major diseases of U.S. farm-raised catfish and were reported to be a problem on about 50% of all catfish operations in 2003. The diseases together cost the U.S. (more) catfish industry $50-$70 million annually. The causative bacteria, Edwardsiella ictalari (E. ictaluri) and Flavobacteri-um columnare (F. columnare), respec-tively, are ubiquitous pathogens that infect all sizes of catfish. No effective control measures were available to the farmer. These pathogens are respon-sible for severe disease outbreaks throughout the catfish industry every year. Previous studies suggested that killed vaccines against both E. ictaluri and F. columnare were not effective when administered by immersions (i.e. mass delivered in the field). The team modified both agents with an antibiotic that changed the lipopolysaccharide (a virulence factor of Gram-negative bacteria). The modified bacteria were still able to gain entry into the fish for a proper immune response to develop, but could no longer cause disease. With the creation of the modified live vaccines, the problems associated with killed vaccines (e.g., injection ad-ministration of each fish, cost of ad-ministration, stress associated with administration, and not providing life-time protection) were overcome.The modified live vaccines are ad-ministered by bath immersion, a non-stressful and inexpensive process, to large numbers of young fish and provide lifelong protection. Both vac-cines were developed under a CRADA with Intervet, Inc., patented, and exclu-sively licensed to Intervet. The CRADA allowed team members to develop the final freeze-dried formulations in coop-eration with Intervet scientists and to cooperatively test the vaccines’ safety and effectiveness. These modified live vaccines are possibly a trend setting ad-vancement for the rest of the world in fish vaccinology. The enteric s e p t i c e-mia vaccine ( A QU AVA C -ESCTM) was first intro-duced in 2001. According to Intervet, the total benefit to producers from use of this vaccine alone is al-most $2,000 per acre, due to faster growing catfish that yield greater lengths over non-vaccinated catfish. AQUAVAC-COLTM, the first ef-ficacious vaccine against columnaris disease in the world, was launched in 2005 and sold out quickly. These vaccines, in combination, provide fish farmers with a cost-effective means of preventing the two most economically serious diseases in commercial pond-raised catfish. (less)