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)
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