Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bacterium causing US catfish deaths has Asian roots

03.06.2014

A bacterium causing an epidemic among catfish farms in the southeastern United States is closely related to organisms found in diseased grass carp in China, according to researchers at Auburn University in Alabama and three other institutions. The study, published this week in mBio®, the online open-access journal of the American Society for Microbiology, suggests that the virulent U.S. fish epidemic emerged from an Asian source.

Since 2009, catfish farming in Alabama, Mississippi and Arkansas has been seriously impacted by an emerging strain of Aeromonas hydrophila, which causes Aeromonas septicemia in catfish. A serious infection that can cause death in as little as 12 hours, Aeromonas septicemia's clinical signs include skin lesions and blood loss.

Normally A. hydrophila, which can be found in both fresh and brackish water, only affects fish that are stressed or injured. But the newer strain has affected even apparently healthy fish with no obvious signs of duress, says senior study author Mark Liles, PhD, an associate professor in the Department of Biological Sciences at Auburn.

When initial tests of the diseased fish showed A. hydrophila was responsible, says Liles, scientists "didn't believe it at first, because the signs didn't match the more typical opportunistic infections in stressed fish that we associate with A. hydrophila." To date, disease outbreaks have been responsible for an estimated loss of more than $12 million in catfish aquaculture operations in the southeastern United States, he says.

Liles and colleagues studied the molecular epidemiology of the epidemic-causing A. hydrophila to try to trace its evolution. They compared samples of the bacteria to 264 known Aeromonas strains in an international database. Only one virulent strain came close to matching the one sampled from Alabama: ZC1, isolated from a diseased grass carp in China's Guangdong Province. ZC1 was isolated from fish that had experienced an epidemic outbreak atypical of Aeromonas infections.

Researchers also identified a less aggressive related A. hydrophila strain called S04-690, taken in 2004 from a diseased catfish in a commercial aquaculture pond in Mississippi. That strain caused a serious Aeromonas septicemia outbreak that killed thousands of catfish but did not result in an epidemic on neighboring farms.

Next, the scientists evaluated the evolutionary relationships of additional Chinese carp bacteria samples from epidemics in the Hubei Province in China. This revealed that all of the Chinese carp bacteria samples, including ZC1, group together with the recent U.S. epidemic samples of bacteria in catfish, suggesting that a common ancestor is responsible for the virulent A. hydrophila strains causing fish disease in both China and the United States.

S04-690, from the Mississippi fish, also was found to be in the same group, related to both the U.S. catfish and Asian carp bacteria. However, it was genetically distinct from the other two strains. By contrast, A. hydrophila strains that do not cause epidemics are more heterogeneous.

Additional experiments found that isolated bacteria from diseased catfish in America and diseased carp in China shared alternate forms of 10 key 'housekeeping' genes required for basic cellular function.

It's not clear how the bacterium was introduced in America, Liles says. It could be from importing Asian carp to America for aquatic weed control, or from transporting ornamental fish or contaminated processed seafood products from Asia. The spread of disease among farms also is not fully understood but could result from birds that move from pond to pond eating catfish, or from harvesting equipment that may be insufficiently sanitized between uses.

Liles and other researchers are investigating means to control the spread of illness, including developing vaccines against the bacteria, and using medicated feed and/or probiotics. Meanwhile, he says, U.S. farmed catfish are safe to eat and pose no disease threat to humans due to strict standards regarding harvesting and processing of sick animals.

###

The study was funded by Auburn University and the Alabama Agricultural Experiment Station.

mBio® is an open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. The focus of the journal is on rapid publication of cutting-edge research spanning the entire spectrum of microbiology and related fields. It can be found online at http://mbio.asm.org.

The American Society for Microbiology is the largest single life science society, composed of over 39,000 scientists and health professionals. ASM's mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.

Jim Sliwa | Eurek Alert!
Further information:
http://www.asmusa.org

Further reports about: Aeromonas bacteria catfish epidemic infections septicemia strains

More articles from Life Sciences:

nachricht Molecular Spies to Fight Cancer - Procedure for improving tumor diagnosis successfully tested
03.08.2015 | Helmholtz-Zentrum Dresden-Rossendorf

nachricht Stroke: news about platelets
03.08.2015 | Julius-Maximilians-Universität Würzburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Glaciers melt faster than ever

Glacier decline in the first decade of the 21st century has reached a historical record, since the onset of direct observations. Glacier melt is a global phenomenon and will continue even without further climate change. This is shown in the latest study by the World Glacier Monitoring Service under the lead of the University of Zurich, Switzerland.

The World Glacier Monitoring Service, domiciled at the University of Zurich, has compiled worldwide data on glacier changes for more than 120 years. Together...

Im Focus: Quantum Matter Stuck in Unrest

Using ultracold atoms trapped in light crystals, scientists from the MPQ, LMU, and the Weizmann Institute observe a novel state of matter that never thermalizes.

What happens if one mixes cold and hot water? After some initial dynamics, one is left with lukewarm water—the system has thermalized to a new thermal...

Im Focus: On the crest of the wave: Electronics on a time scale shorter than a cycle of light

Physicists from Regensburg and Marburg, Germany have succeeded in taking a slow-motion movie of speeding electrons in a solid driven by a strong light wave. In the process, they have unraveled a novel quantum phenomenon, which will be reported in the forthcoming edition of Nature.

The advent of ever faster electronics featuring clock rates up to the multiple-gigahertz range has revolutionized our day-to-day life. Researchers and...

Im Focus: Superfast fluorescence sets new speed record

Plasmonic device has speed and efficiency to serve optical computers

Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second and could form the basis of optical computing.

Im Focus: Unlocking the rice immune system

Joint BioEnergy Institute study identifies bacterial protein that is key to protecting rice against bacterial blight

A bacterial signal that when recognized by rice plants enables the plants to resist a devastating blight disease has been identified by a multi-national team...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Euro Bio-inspired - International Conference and Exhibition on Bio-inspired Materials

23.07.2015 | Event News

Clash of Realities – International Conference on the Art, Technology and Theory of Digital Games

10.07.2015 | Event News

World Conference on Regenerative Medicine in Leipzig: Last chance to submit abstracts until 2 July

25.06.2015 | Event News

 
Latest News

Reliable and extremely long-lasting – high-voltage power electronics for network expansion

04.08.2015 | Power and Electrical Engineering

Riding a horse is far more complex than riding simulators

04.08.2015 | Agricultural and Forestry Science

CO2 removal cannot save the oceans – if we pursue business as usual

04.08.2015 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>