Overview of spatio-temporal distribution inferred by multi-locus sequence typing of Taylorella equigenitalis isolated worldwide from 1977 to 2018 in equidae.

Overview

This study investigates the identification of different strains of Taylorella equigenitalis, a bacteria causing contagious equine metritis (CEM), a sexually transmitted disease in horses. The researchers used multilocus sequence typing to compare 367 strains of the bacteria from different locations, times, and horse breeds. They found low genetic heterogeneity but wide geographical distribution, some strain types with cross-border circulation, and long-standing circulation of major strain-types in specific areas.

Detailed Explanation

This research paper looks into the study of Taylorella equigenitalis, the bacterium that causes contagious equine metritis (CEM), an infectious disease of horses that is commonly sexually transmitted.

• Researchers performed multilocus sequence typing, a technique used to distinguish bacterial strains, on 367 types of the bacteria originating from different countries and isolated from various horse breeds over a span of 41 years (1977-2018).
• 49 sequence types (STs) were identified, with 10 described for the first time. The study also managed to categorize the strains into three major and three minor clonal complexes (CCs), groups representing strains of the bacterium that share a recent common ancestor. Apart from that, 11 strains were identified that did not belong to any specific group or clonal complex and were termed as ‘singletons’.
• Despite the varied scope of the study, it found low genetic heterogeneity (variation) amongst the strains, only at a rate of 0.13 STs per strain, indicating the common genetic make-up of this bacterium regardless of its geographical location or the year of isolation.
• Higher variation was observed outside Europe and during the 1977-1997 period. The research indicates the existing major sequence types and clonal complexes were already present before 1998.
• The study corroborates previous research associating Clonal Complex 1 (CC1) with the first CEM outbreaks in the United Kingdom, Australia, and the United States in 1977-78. This study also confirmed the circulation of CC1 in France for a longer period from 1992 to 2018, extending to Spain and Germany as well.
• Besides, the movement of certain strains between non-European and European countries was identified only through ST4, ST17, and ST30.
• Within Europe, there was evidence of cross-border movement of specific bacteria strains, particularly ST16 and ST46 from the major clonal complexes CC2 and CC8.
• This study’s findings provide a foundation for monitoring and controlling the spread of CEM outbreaks in the future. However, the authors suggest that performing a retrospective analysis on a greater number of global strains isolated between 1977 and the early 2000s will provide a more comprehensive understanding of the original situation of CEM.