New catfish vaccines developed by ARS

Two new fish vaccines developed by Agricultural Research Service (ARS) scientists could save producers millions of dollars while lowering costs to consumers.

Two immersion-applied, modified live vaccines for farm-raised catfish and other species have been developed at the ARS Aquatic Animal Health Research Unit in Auburn, Ala., and at a unit branch in Chestertown, Md.

Fish are susceptible to diseases and need vaccines, but it's not easy to inject fish. So scientists try to develop vaccines that can be administered by immersion in water.

The two vaccines, which provide protection against Flavobacterium columnare, have been developed by ARS, and each works differently. One vaccine, developed by ARS microbiologist Craig A. Shoemaker at Auburn, is effective and has been field tested by Intervet, Inc., Millsboro, Del. This modified live vaccine cannot cause disease, but can persist long enough to stimulate immunity.

The other vaccine, developed by ARS molecular biologist Joel A. Bader at Auburn, does not allow a pathogen to colonize, yet allows enough pathogen to persist for immunity to develop. F. columnare, the second leading cause of catfish fatality, also affects many other fish species.

Two types of bacteria causing worldwide problems, Streptococcus iniae and Streptococcus algalactiae, are being treated with killed vaccines. Both bacteria cause streptococcal disease, but antibiotics do not work well against them. Killed vaccines, done by injection, are not as efficient as immersion, but research leader Phillip H. Klesius, a microbiologist at Auburn, believes research will produce an immersion vaccine for these Streptococcus bacteria.

Joyce J. Evans, an aquatic pathologist with ARS in Chestertown, has worked on several vaccines and developed a modified live vaccine for treating Edwardsiella tarda, another disease affecting several species. E. tarda is both costly and a nuisance, since fish processors must shut down and disinfect entire production lines. This fish pathogen is also a human pathogen transmissible through skin punctures and ingestion of contaminated fish.

ARS is the U.S. Department of Agriculture's chief in-house scientific research agency.

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