WWI-Era Bacteria: The Key to Eradicating Strangles?
The current S. equi strain didn’t appear until around the time of World War I. | Photo: Courtesy of the Swiss Federal Archives/Wikimedia Commons
In the war against strangles, researchers believe they’ve discovered a critical genomic influence: war.

Although veterinarians have been diagnosing strangles since the 13th century, the current strain of the causative agent didn’t appear until the early 20th century. Specifically, it was around the time of World War I.

Hoping to create a vaccine that would ward off all existing variants of Streptococcus equi (S. equi), the bacteria that causes strangles, British researchers started mapping bacterial genomes. They investigated the DNA of 224 S. equi samples from around the world to find a common genomic ancestor to this approximately 800-year-old agent. But to their surprise, the samples were very closely related. And they all appeared to have been derived from common ancestors dating back only about 100 years.

“S. equi has been infecting horses for many hundreds of years, but it appears that the older strains have died out, being replaced by what we see today,” said Andrew Waller, BSc, PhD, from the Animal Health Trust, in Newmarket, U.K

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