Featured Research

from universities, journals, and other organizations

Scientists unlock evolution of cholera, identify strain responsible for early pandemics that killed millions

Date:
January 9, 2014
Source:
McMaster University
Summary:
Working with a nearly 200-year-old sample of preserved intestine, researchers have traced the bacterium behind a global cholera pandemic that killed millions – a version of the same bug that continues to strike vulnerable populations in the world’s poorest regions.

Using sophisticated techniques, the team has mapped the entire genome of the elusive 19th century cholera bacterium. The findings are significant because, until now, researchers had not identified the early strains of cholera, a water-borne pathogen. The discovery significantly improves understanding of the pathogen’s origin and creates hope for better treatment and possible prevention.
Credit: McMaster University

Working with a nearly 200-year-old sample of preserved intestine, researchers at McMaster University and the University of Sydney have traced the bacterium behind a global cholera pandemic that killed millions -- a version of the same bug that continues to strike vulnerable populations in the world's poorest regions.

Using sophisticated techniques, the team has mapped the entire genome of the elusive 19th century bacterium. The findings are significant because, until now, researchers had not identified the early strains of cholera, a water-borne pathogen. The discovery significantly improves understanding of the pathogen's origin and creates hope for better treatment and possible prevention.

Researchers have now confirmed the first of two types of cholera, known as classical, was likely responsible for five of the seven devastating outbreaks in the 1800s, all of which most likely originated in waters of the Bay of Bengal.

That strain of cholera had remained a mystery because researchers were unable to examine samples from early victims. The pathogen thrives in the intestines, never reaching teeth or bones, so remnants of its DNA do not exist in skeletal remains. Despite many known cholera burials, access to historical cholera DNA had seemed impossible since it can only be found in soft-tissue remains.

But graduate student Alison Devault and evolutionary geneticists Hendrik Poinar, Brian Golding and Eddie Holmes -- working with a team of other scientists -- learned that a remarkable collection of tissue specimens was housed at a medical history museum. The Mütter Museum was established by the College of Physicians of Philadelphia in 1858, after the city itself was devastated by cholera earlier in the century.

Researchers carefully sampled a preserved intestine from a male victim of the 1849 pandemic and extracted information from tiny DNA fragments to reconstruct the Vibrio cholera genome.

The results, currently published in The New England Journal of Medicine, could lead to a better understanding of cholera and its modern-day strain known as El Tor, which replaced the classical strain in the 1960s for unknown reasons and is responsible for recent epidemics, including the devastating post-earthquake outbreak in Haiti.

"Understanding the evolution of an infectious disease has tremendous potential for understanding its epidemiology, how it changes over time, and what events play a role in its jump into humans," explains Poinar, associate professor and director of the McMaster Ancient DNA Centre and an investigator with the Michael G. DeGroote Institute of Infectious Disease Research, also at McMaster University.

"We need to understand the selective pressures on the pathogen which in turn is driving its evolution, its virulence and hopefully use that information to develop better treatments," he says. Using a sophisticated technique to extract, purify and enrich fragments of the pathogen's DNA, the team collected precious genomic data, which answered many unresolved questions.

The researchers identified "novel genomic islands," or genome regions that don't occur in current strains. In addition, a well-known genic region involved in toxicity of the pathogen (a sequence called "CTX") occurs more times in the ancient strain than in its modern descendants.

This may mean that this strain was more virulent, say researchers, but further testing will be needed.

Regarding the origins, the team's calculations show that the classical strain and El Tor co-existed in humans and estuaries for many centuries, potentially thousands of years prior to the 19th century pandemics, and emerged as a full-blown infection in humans in the early 1800's.

The ancestor of both the classical and El Tor strain likely circulated together in the waters of the Bay of Bengal for several thousand years before emerging in humans during what is known as the first epidemiological transition, or a time of great agricultural revolution and human settlement.

The World Health Organization estimates there are three to five million new cholera cases every year. Of those, 100,000 to 120,000 people typically die from the disease. But with access to historical collections and samples, scientists hope to gain a better understanding of how pandemics arise, spread and ultimately how they might be better controlled or stopped.

"The genomes of ancestral pathogens that have descendants today reside in these archival medical collections all over the world," says Poinar. "We have access to hundreds of thousands of ancient specimens, which hold tremendous potential to determine the origins of past epidemics." Thus these collections represent a treasure trove and should be carefully preserved and maintained.


Story Source:

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


Journal Reference:

  1. Alison M. Devault, G. Brian Golding, Nicholas Waglechner, Jacob M. Enk, Melanie Kuch, Joseph H. Tien, Mang Shi, David N. Fisman, Anna N. Dhody, Stephen Forrest, Kirsten I. Bos, David J.D. Earn, Edward C. Holmes, Hendrik N. Poinar. Second-Pandemic Strain ofVibrio choleraefrom the Philadelphia Cholera Outbreak of 1849. New England Journal of Medicine, 2014; 140108140136001 DOI: 10.1056/NEJMoa1308663

Cite This Page:

McMaster University. "Scientists unlock evolution of cholera, identify strain responsible for early pandemics that killed millions." ScienceDaily. ScienceDaily, 9 January 2014. <www.sciencedaily.com/releases/2014/01/140109003802.htm>.
McMaster University. (2014, January 9). Scientists unlock evolution of cholera, identify strain responsible for early pandemics that killed millions. ScienceDaily. Retrieved September 2, 2014 from www.sciencedaily.com/releases/2014/01/140109003802.htm
McMaster University. "Scientists unlock evolution of cholera, identify strain responsible for early pandemics that killed millions." ScienceDaily. www.sciencedaily.com/releases/2014/01/140109003802.htm (accessed September 2, 2014).

Share This




More Fossils & Ruins News

Tuesday, September 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Did Neanderthals Play Tic-Tac-Toe?

Did Neanderthals Play Tic-Tac-Toe?

Newsy (Sep. 2, 2014) — Artwork found in a Gibraltar cave that was possibly done by Neanderthals suggests they may have been smarter than we all thought. Video provided by Newsy
Powered by NewsLook.com
Millions Of Historical Public Domain Photos Added To Flickr

Millions Of Historical Public Domain Photos Added To Flickr

Newsy (Aug. 30, 2014) — Historian Kalev Leetaru uploaded a large collection of historical photos, images that were previously difficult to collect. Video provided by Newsy
Powered by NewsLook.com
Minds Blown: Scientists Develop Fish That Walk On Land

Minds Blown: Scientists Develop Fish That Walk On Land

Newsy (Aug. 28, 2014) — Canadian scientists looking into the very first land animals took a fish out of water and forced it to walk. Video provided by Newsy
Powered by NewsLook.com
Huge Ancient Wine Cellar Found In Israel

Huge Ancient Wine Cellar Found In Israel

Newsy (Aug. 28, 2014) — An international team uncovered a large ancient wine celler that likely belonged to a Cannonite ruler. 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:
from the past week

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