Protecting Fish Through Vaccines
Just as humans need vaccines to prevent dangerous diseases like polio and
measles, fish too can benefit from vaccines against their own set of diseases.
Microbiologist Phillip Klesius gives catfish feed that
has been supplemented with vaccine at the Aquatic Animal Health Research
Unit in Auburn, Alabama.
Several researchers at the ARS Aquatic
Animal Health Research Unit in Auburn, Alabamaalong with one from their
laboratory in Chestertown, Marylandare working mainly with catfish and
to a lesser extent with tilapia, hybrid striped bass, and several other species
of fish, to develop fish vaccines to protect against diseases. Many of the diseases
kill the fish, which means less profit for the producer and higher prices for
Over the last few years, the laboratory has either patented or applied for
patents for several fish vaccines. It takes about 2 to 4 years of research
to get to the point where we can apply for a patent, explains microbiologist
Craig A. Shoemaker. Hes helped to develop several vaccines in Auburn.
After the vaccine is patented, ARS will license it to a company. Because of
the additional testing required by regulatory agencies, it might take another
5 years or more to get the vaccine on the market. Shoemaker says that to cut
down on this time, the researchers will often work with companies early on to
develop and test the vaccines.
At the Aquatic Animal Health Research Unit's Chestertown,
Maryland, site, veterinary medical officer David Pasnik weighs and measures
a tilapia fish while aquatic pathologist Joyce Evans injects another one
with a vaccine.
In June 2004, the lab submitted a patent application for a modified live vaccine
(meaning the fish are subjected to live bacteria) against Flavobacterium
columnare. This bacteria causes columnaris disease, which affects many varieties
of fisheverything from catfish to goldfishand thus has a large economic
impact. Its the second leading cause of death for catfish. The researchers
believe fish producers will save $100 million a year with this vaccine. Currently,
fish producers treating for columnaris either apply chemicals to the water or
give the fish special food, but this vaccinegiven through a bathis
much more effective.
At the laboratory, molecular biologist Joel A. Bader has also applied for a
patent for a modified live F. columnare vaccine against columnaris disease.
The two vaccines were developed independently of each other. Both vaccines
are effective against the disease but work in different ways, Bader says.
Baders vaccine was modified to prevent the bacteria from attaching to
the fish, yet will allow the bacteria to live long enough for the fish to become
While some fish vaccines are injectedjust like many human vaccines areresearchers
are trying to move away from that, since its not efficient to hand vaccinate
thousands of fish. With either of these two Flavobacterium vaccines,
both given as a bath at an early age, hundreds of thousands of fish can be vaccinated
in as little as 10 minutes. When the fish are moved from a farm to the producers
pond, theyll be protected.
The researchers have also worked on vaccines to fight two strains of Streptococcus
bacteria, a worldwide disease problem. Antibiotics do not work well against
these bacteria. For Streptococcus iniae, a disease found in 22
species of cultured and wild fish such as tilapia and rainbow trout, the scientists
have developed a successful killed vaccine. Weve found that its
more effective when given by injection, says microbiologist and research
leader Phillip H. Klesius. Its time consuming, but doable.
The group received a patent for this vaccine in 2002.
The scientists also developed a killed vaccine for Streptococcus agalactiae,
a similar bacterium. Klesius believes an immersion vaccine may be possible in
the future. This disease can also infect humans and cattle.
The group is working with the Canadian company PerOs Systems Technologies to
develop an oral delivery method for killed vaccines. Initial tests have been
positive. An oral vaccine would likely be cheaper and easier to administer than
an injection or immersion vaccine.
A lot of work for several of these vaccines was done by ARS aquatic pathologist
Joyce J. Evans in Chestertown, Maryland. She says her laboratory is more for
conducting vaccine trials on the fish rather than manufacturing the vaccines,
since its a smaller facility. The lab focuses on tilapia.
Evans has also helped to develop a modified live Edwardsiella tarda
vaccine. Like the other bacteria, this one infects many species of fish. The
disease is not just costly; its also a nuisance. If a producer detects
the bacterium, processing lines need to be shut down and disinfected. The disease
can also be passed on to humans. Up to this point, some producers use medicated
feed to stop the disease from spreading, but its not very effective. The
new vaccine could save producers millions of dollars each year.By David Elstein, formerly
This research is part of Aquaculture, an ARS National Program (#106) described
on the World Wide Web at www.nps.ars.usda.gov.
Phillip H. Klesius,
Craig A. Shoemaker,
and Joel A. Bader are
in the USDA-ARS Aquatic
Animal Health Research Unit, 990 Wire Rd., Auburn, AL 36832; phone (334)
887-3741, fax (334) 887-2983.
Joyce J. Evans is
with the USDA-ARS Aquatic
Animal Health Research Unit, 151 Dixon Dr., Chestertown, MD 21620; phone
(410) 778-2120, fax (410) 778-4399.
"Protecting Fish Through Vaccines" was published in the May
2005 issue of Agricultural Research magazine.