Veterinarians and horse handlers should be aware that Streptococcus equi, the organism responsible for strangles, may survive in the environment for longer than previously thought, according to new research.
The study, by Andy Durham and colleagues, has been reported in the Equine Veterinary Journal.
The researchers inoculated S. equi cultures onto seven surfaces found in veterinary practices or in stables, and took serial samples to see how long the organism remained viable.
The test surfaces included a wet plastic bucket, a dental rasp, inside a naso-gastric tube and a fence post. Samples were taken frequently from each of the inoculated sites and cultured, until it was no longer possible to find the organism. The procedure was carried out in both the summer and winter. Inoculated surfaces were kept out of direct sunlight for the duration of the study.
The researchers found that the bacteria survived longest in wet, humid, and cold conditions, while survival tended to be short in the summer (up to 9 days in wet sites and up to 2 days in dry sites.
S. equi was recorded for up to 34 days in a wet bucket in the winter. The most vigorous growth was obtained from inside a moist naso-gastric tube, where the organism survived for up to 21 days in the winter.
The report’s authors conclude that S. equi may survive in the environment for far longer than has been reported previously: “Although survival in warm and dry locations was detected for only up to 2 days, in wet and cold indoor conditions S. equi may remain viable for more than 30 days.”
“Although extrapolation to natural infection and transmissibility is difficult, the possibility that similarly prolonged survival could occur following outbreaks of clinical disease should be considered as part of the formulation of control strategies.”
For more details, see:
A study of the environmental survival of Streptococcus equi subspecies equi
A. E. Durham, Y. S. Hall, L. Kulp, C. Underwood
Equine Veterinary Journal (2018)