Globetrotting strangles: the unbridled national and international transmission of Streptococcus equi between horses

Abstract

The equine disease strangles, which is characterized by the formation of abscesses in the lymph nodes of the head and neck, is one of the most frequently diagnosed infectious diseases of horses around the world. The causal agent, Streptococcus equi subspecies equi , establishes a persistent infection in approximately 10 % of animals that recover from the acute disease. Such ‘carrier’ animals appear healthy and are rarely identified during routine veterinary examinations pre-purchase or transit, but can transmit S. equi to naïve animals initiating new episodes of disease. Here, we report the analysis and visualization of phylogenomic and epidemiological data for 670 isolates of S. equi recovered from 19 different countries using a new core-genome multilocus sequence typing (cgMLST) web bioresource. Genetic relationships among all 670 S. equi isolates were determined at high resolution, revealing national and international transmission events that drive this endemic disease in horse populations throughout the world. Our data argue for the recognition of the international importance of strangles by the Office International des Épizooties to highlight the health, welfare and economic cost of this disease. The Pathogenwatch cgMLST web bioresource described herein is available for tailored genomic analysis of populations of S. equi and its close relative S. equi subspecies zooepidemicus that are recovered from horses and other animals, including humans, throughout the world. This article contains data hosted by Microreact.

One clone to rule them all: Culture-independent genomics of Chlamydia psittaci from equine and avian hosts in Australia

“…Furthermore, the global movement of horses for breeding, training and/or competition purposes is a common practice [ 48 ]. However, such practice may facilitate the unconstrained international transmission of chlamydial infections, such as observed for Streptococcus equi subspecies equi , the causative agent of strangles [ 49 ]. As such, the equine C. psittaci sub-lineages represent contemporary strains causing reproductive loss across Australia.…”

Streptococcus equi subsp. equi in Retropharyngeal Abscess: Case Report and Review of Literature

“…Moreover, horses from the stable were under the care of qualified veterinarians. All horses should be examined by veterinarians before and after transport to decrease the risk of disease transmission [ 31 ]. According to Newton et al [ 32 ], horses, that have recovered from infection caused by S. equi , even though they do not present any symptoms, are still a carrier of the pathogen.…”

Repeated nasopharyngeal lavage predicts freedom from silent carriage of Streptococcus equi after a strangles outbreak

“…Carriers are undoubtedly key offenders in the spread of strangles to naïve horses, and indeed persistence of this disease worldwide. 5 …”

“…Recognition of the carrier state 2 (predicted early in the 1900's 3 ) and awareness that the organism could persist in the guttural pouches 4 were key advances in understanding the overall epizootiology of strangles and how it may persist and spread to immunologically susceptible horses. Carriers are undoubtedly key offenders in the spread of strangles to naïve horses, and indeed persistence of this disease worldwide 5 …”

“…Carriers are undoubtedly key offenders in the spread of strangles to naïve horses, and indeed persistence of this disease worldwide. 5 Two recent American College of Veterinary Internal Medicine (ACVIM)consensus statements on strangles management indicate that detection of the carrier state for S. equi requires either repeated nasopharyngeal lavage (NPL) or direct sampling from the guttural pouch. The initial consensus statement of 2005 6 advised that consistent negatives for S. equi on PCR from 3 consecutive weekly sampling of nasopharyngeal swabs or lavages were sufficient to allow horses to return to a "clean" noninfected group.…”