Featured Research

from universities, journals, and other organizations

Bacterium causing U.S. catfish deaths has Asian roots

Date:
June 3, 2014
Source:
American Society for Microbiology
Summary:
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. The study suggests that the virulent US fish epidemic emerged from an Asian source.

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.

Related Articles


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.


Story Source:

The above story is based on materials provided by American Society for Microbiology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Mohammad J. Hossain, Dawei Sun, Donald J. McGarey, Shannon Wrenn, Laura M. Alexander, Maria Elena Martino, Ye Xing, Jeffery S. Terhune, and Mark R. Liles. An Asian Origin of Virulent Aeromonas hydrophila Responsible for Disease Epidemics in United States-Farmed Catfish. mBio, 5:3 May/June 2014 DOI: 10.1128/mBio.00848-14

Cite This Page:

American Society for Microbiology. "Bacterium causing U.S. catfish deaths has Asian roots." ScienceDaily. ScienceDaily, 3 June 2014. <www.sciencedaily.com/releases/2014/06/140603092426.htm>.
American Society for Microbiology. (2014, June 3). Bacterium causing U.S. catfish deaths has Asian roots. ScienceDaily. Retrieved March 27, 2015 from www.sciencedaily.com/releases/2014/06/140603092426.htm
American Society for Microbiology. "Bacterium causing U.S. catfish deaths has Asian roots." ScienceDaily. www.sciencedaily.com/releases/2014/06/140603092426.htm (accessed March 27, 2015).

Share This


More From ScienceDaily



More Plants & Animals News

Friday, March 27, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Jockey Motion Tracking Reveals Racing Prowess

Jockey Motion Tracking Reveals Racing Prowess

Reuters - Innovations Video Online (Mar. 26, 2015) — Using motion tracking technology, researchers from the Royal Veterinary College (RVC) are trying to establish an optimum horse riding style to train junior jockeys, as well as enhance safety, health and well-being of both racehorses and jockeys. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Bear Cubs Tumble for the Media

Bear Cubs Tumble for the Media

Reuters - Light News Video Online (Mar. 26, 2015) — Two Andean bear cubs are unveiled at the U.S. National Zoo in Washington, D.C. Alicia Powell reports. Video provided by Reuters
Powered by NewsLook.com
Botswana Talks to End Illegal Wildlife Trade

Botswana Talks to End Illegal Wildlife Trade

AFP (Mar. 25, 2015) — Experts are gathering in Botswana to try to end the illegal wildlife trade that is decimating populations of elephants, rhinos and other threatened species. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
Elephants Help Keep 18-Wheeler From Toppling Over

Elephants Help Keep 18-Wheeler From Toppling Over

Newsy (Mar. 25, 2015) — The Natchitoches Parish Sheriff&apos;s Office discovered two elephants keeping a tractor-trailer that had gotten stuck in some mud upright on a highway. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins