Origins of Dysentery

A new genomic analysis reveals that the pathogen responsible for the gastrointestinal disease likely originated in Europe and hitched a ride to new lands with settlers.

Bob Grant
Bob Grant
Mar 21, 2016

A stool sample from a patient infected with Shigella dysenteriaeWIKIMEDIA, CDCShigella dysenteriae, the bacterium that causes dysentery, originated in Europe and was spread to the rest of the world decades ago by emigrants and colonizers, according to a new genomic analysis of hundreds of strains of the pathogen. Researchers and historians previously suspected that European travelers had brought the deadly disease back with them from South America, Asia, or Africa. But the new findings, published in Nature Microbiology this week (March 21), tell a different tale.

An international team used high-throughput technology to sequence more than 300 strains of type 1 S. dysenteriae in samples collected from the early 20th century until 2011 at sites around the globe. The researchers detailed differences in the strains that caused various outbreaks throughout history, and surmised that type 1 S. dysenteriae dates to at least the 18th century.

“Analyzing the full genomes of all these Shigella dysenteriae strains collected over a huge timeframe and from such an array of different countries provided us with an unprecedented insight into the historical spread of this pathogen,” study coauthor Nicholas Thomson, leader of the Bacterial Genomics and Evolution group at the Sanger Institute in the U.K., said in a statement. “This was needed because there are still many unanswered questions relating this infamous and important bacterial pathogen. It was achieved by combining high resolution genomic research data with the detailed information recording the provenance of each sample from a large number of dedicated groups.”

Dysentery still plagues human populations in Asia, Africa, and the Americas, with the last major outbreak killing 20,000 Central Americans between 1969 and 1972. To that end, the researchers also detected genomic signals pointing to the development of antibiotic resistance, which has left only 1 percent of circulating S. dysenteriae strains vulnerable to antibiotics since the 1990s. “This bacterium is still in circulation, and could be responsible for future epidemics if conditions should prove favorable—such as a large gathering of people without access to drinking water or treatment of human waste,” study coauthor François-Xavier Weill of the Pasteur Institute’s Enteric Bacterial Pathogens Unit said in the statement. “This study highlights the need for an effective vaccine, which will be crucial for controlling this disease in the future in view of the reduced efficacy of antibiotics.”