Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide







  • Last modified
  • 22 November 2019
  • Datasheet Type(s)
  • Animal Disease
  • Preferred Scientific Name
  • strangles
  • Pathogens
  • Streptococcus equi subsp. equi
  • Overview
  • Strangles is a highly contagious respiratory disease of horses, donkeys and mules caused by the bacterium Streptococcus equi subspecies equi (S. equi). It is one of the most prevalent equine infectious diseases worldwi...

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Preferred Scientific Name

  • strangles


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Streptococcus equi subsp. equi


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Strangles is a highly contagious respiratory disease of horses, donkeys and mules caused by the bacterium Streptococcus equi subspecies equi (S. equi). It is one of the most prevalent equine infectious diseases worldwide, with significant welfare and economic costs (Harrington et al. 2002; Waller, 2013). Morbidity may be high, but mortality is usually low (Mallicote, 2015).

The classical disease is an upper respiratory infection characterised by pyrexia, coughing, profuse mucopurulent nasal discharge, enlargement of the lymph nodes draining the upper respiratory tract, and subsequent abscessation of these lymph nodes (Yelle, 1987). Rarely, this lymph node enlargement can cause inspiratory stridor and dyspnoea and it is this clinical feature that gave the disease its name. Treatment is dependent on the stage and severity of disease (Sweeney et al., 2005; Taylor and Wilson, 2006).

S. equi is an obligate equine pathogen, surviving for only short periods in the environment (Weese et al. 2009). Transmission occurs through oral and nasal routes directly and through contact with contaminated surfaces indirectly (Sweeney et al., 2005). Subclinical carriers that intermittently shed bacteria may act as sources of infection for naïve animals for up to several months or even years (Newton et al., 2000). The standard site of prolonged carriage of S. equi in these horses is the guttural pouches (Sweeney et al., 2005). Recognition and detection of this category of transmission is necessary for successful elimination of the disease from a farm (Waller and Jolley, 2007; Waller et al., 2011). New qPCR and iELISA diagnostic tests have replaced culture methodologies as the gold standard for the detection of infected animals (Waller, 2013). In the future, the ability to use modern vaccines alongside conventional biosecurity and screening procedures will be critical to the large-scale prevention of strangles (Waller, 2013).

Host Animals

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Animal nameContextLife stageSystem
Equus asinus (donkeys)
Equus caballus (horses)


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Strangles is the most frequently diagnosed infectious disease of horses worldwide (Harris et al., 2015).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 10 Jan 2020
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes


BurundiAbsent, No presence record(s)
Cabo VerdeAbsent, No presence record(s)
Central African RepublicAbsent, No presence record(s)
Congo, Democratic Republic of theAbsent, No presence record(s)
Côte d'IvoireAbsent, No presence record(s)
DjiboutiAbsent, No presence record(s)
EswatiniAbsent, No presence record(s)
GhanaAbsent, No presence record(s)
GuineaAbsent, No presence record(s)
LibyaAbsent, No presence record(s)
MadagascarAbsent, No presence record(s)
MauritiusAbsent, No presence record(s)
SeychellesAbsent, No presence record(s)
South AfricaPresent
SudanAbsent, No presence record(s)
TogoAbsent, No presence record(s)
UgandaAbsent, No presence record(s)
ZambiaAbsent, No presence record(s)


BahrainAbsent, No presence record(s)
GeorgiaAbsent, No presence record(s)
Hong KongAbsent, No presence record(s)
IndiaAbsent, No presence record(s)
IndonesiaAbsent, No presence record(s)
IranAbsent, No presence record(s)
JordanAbsent, No presence record(s)
KazakhstanAbsent, No presence record(s)
-Peninsular MalaysiaAbsent, No presence record(s)
-SabahAbsent, No presence record(s)
-SarawakAbsent, No presence record(s)
North KoreaAbsent, No presence record(s)
OmanAbsent, No presence record(s)
Saudi ArabiaAbsent, No presence record(s)
SingaporeAbsent, No presence record(s)
Sri LankaAbsent, No presence record(s)
SyriaAbsent, No presence record(s)
TaiwanAbsent, No presence record(s)
ThailandAbsent, No presence record(s)
VietnamAbsent, No presence record(s)


AndorraAbsent, No presence record(s)
BelarusAbsent, No presence record(s)
EstoniaAbsent, No presence record(s)
GreeceAbsent, No presence record(s)
IcelandAbsent, No presence record(s)
LiechtensteinAbsent, No presence record(s)
LuxembourgAbsent, No presence record(s)
MaltaAbsent, No presence record(s)
North MacedoniaAbsent, No presence record(s)
PortugalAbsent, No presence record(s)
RomaniaAbsent, No presence record(s)
SlovakiaAbsent, No presence record(s)
SloveniaAbsent, No presence record(s)
SpainAbsent, No presence record(s)
UkraineAbsent, No presence record(s)
United Kingdom
-Northern IrelandPresent

North America

BelizeAbsent, No presence record(s)
BermudaAbsent, No presence record(s)
British Virgin IslandsAbsent, No presence record(s)
Cayman IslandsAbsent, No presence record(s)
CubaAbsent, No presence record(s)
CuraçaoAbsent, No presence record(s)
DominicaAbsent, No presence record(s)
Dominican RepublicAbsent, No presence record(s)
GuatemalaAbsent, No presence record(s)
HaitiAbsent, No presence record(s)
HondurasAbsent, No presence record(s)
JamaicaAbsent, No presence record(s)
MexicoAbsent, No presence record(s)
NicaraguaAbsent, No presence record(s)
PanamaAbsent, No presence record(s)
Saint Kitts and NevisAbsent, No presence record(s)
Saint Vincent and the GrenadinesAbsent, No presence record(s)
Trinidad and TobagoAbsent, No presence record(s)
United StatesPresent


French PolynesiaAbsent, No presence record(s)
New CaledoniaAbsent, No presence record(s)
New ZealandPresent
VanuatuAbsent, No presence record(s)

South America

BrazilAbsent, No presence record(s)
ColombiaAbsent, No presence record(s)
GuyanaAbsent, No presence record(s)
VenezuelaAbsent, No presence record(s)


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Harrington DJ; Sutcliffe IC; Chanter N, 2002. The molecular basis of Streptococcus equi infection and disease. Microbes and Infection, 4(4):501-510.

Harris SR; Robinson C; Steward KF; Webb KS; Paillot R; Parkhill J; Holden MTG; Waller AS, 2015. Genome specialization and decay of the strangles pathogen, Streptococcus equi, is driven by persistent infection. Genome Research, 25(9):1360-1371.

Mallicote M, 2015. Update on Streptococcus equi subsp equi infections. Veterinary Clinics of North America, Equine Practice, 31(1):27-41.

Newton JR; Verheyen K; Talbot NC; Timoney JF; Wood JLN; Lakhani KH; Chanter N, 2000. Control of strangles outbreaks by isolation of guttural pouch carriers identified using PCR and culture of Streptococcus equi. Equine Veterinary Journal, 32(6):515-526.

OIE Handistatus, 2002. World Animal Health Publication and Handistatus II (dataset for 2001). Paris, France: Office International des Epizooties.

OIE Handistatus, 2003. World Animal Health Publication and Handistatus II (dataset for 2002). Paris, France: Office International des Epizooties.

OIE Handistatus, 2004. World Animal Health Publication and Handistatus II (data set for 2003). Paris, France: Office International des Epizooties.

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (data set for 2004). Paris, France: Office International des Epizooties.

Sweeney C; Timoney JF; Newton JR; Hines MT, 2005. Review of Streptococcus equi infections in horses: guidelines for treatment, control, and prevention of strangles. In: Proceedings of the 51st Annual Convention of the American Association of Equine Practitioners, Seattle, Washington, USA, 3-7 December, 2005 [ed. by Brokken, T. D.]. Lexington, USA: American Association of Equine Practitioners (AAEP), 163-170.

Taylor SD; Wilson WD, 2006. Streptococcus equi subsp. equi (strangles) infection. Clinical Techniques in Equine Practice, 5(3):211-217.

Waller AS, 2013. Strangles: taking steps towards eradication. Veterinary Microbiology, 167(1/2):50-60.

Waller AS; Jolley KA, 2007. Getting a grip on strangles: recent progress towards improved diagnostics and vaccines. Veterinary Journal, 173(3):492-501.

Waller AS; Paillot R; Timoney JF, 2011. Streptococcus equi: a pathogen restricted to one host. Journal of Medical Microbiology, 60(9):1231-1240.

Weese JS; Jarlot C; Morley PS, 2009. Survival of Streptococcus equi on surfaces in an outdoor environment. Canadian Veterinary Journal, 50(9):968-970.

Yelle MT, 1987. Clinical aspects of Streptococcus equi infection. Equine Veterinary Journal, 19(2):158-162.

Distribution References

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (dataset for 2004)., Paris, France: Office International des Epizooties.

Distribution Maps

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