Genomic Dissection of an Icelandic Epidemic of Respiratory Disease in Horses and Associated Zoonotic Cases

Sigríður Björnsdóttir, Simon R. Harris, Vilhjálmur Svansson, Eggert Gunnarsson, Ólöf G. Sigurðardóttir, Kristina Gammeljord, Karen F. Steward, J. Richard Newton, Carl Robinson, Amelia R. L. Charbonneau, Julian Parkhill, Matthew T. G. Holden, Andrew S. Waller
  • mBio, August 2017, ASM Journals
  • DOI: 10.1128/mbio.00826-17

Whole genome sequencing identifies cause of zoonotic epidemic

What is it about?

For the first time ever, whole genome sequencing was used to identify the cause of a zoonotic infection that sparked a national epidemic of respiratory disease that spread through the population of 80,000 native horses in Iceland during 2010. The bacterium Streptococcus zooepidemicus was recovered from affected horses, humans, dogs and cats. Sequencing these bacteria enabled the differentiation of the epidemic strain, ST209, from endemic strains, revealing its disease-causing potential.

Why is it important?

Previously, researchers have used whole genome sequencing to determine how pathogens spread through a hospital, but this is the first time the technology has been used to track the outbreak of a zoonotic disease.


Andrew Waller
Animal Health Trust

Strains of the bacteria Streptococcus zooepidemicus are genetically highly diverse and can persist in recovered horses confounding the identification of pathogenic variants. The exquisite resolution of strains provided by whole genome sequencing enabled us to identify which strains were normally present in the Icelandic horse population and which was the epidemic strain that was causing the problem. We were also able to trace the origins of the epidemic to a single farm within Iceland, where the training of horses using a submerged treadmill may have facilitated transmission of S. zooepidemicus.

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The following have contributed to this page: Andrew Waller