AAEP InfectiousDisease Guidelines: Strangles STRANGLES (STREPTOCOCCUS EQUI SUBSPECIES EQUI)


Definition Clinical Signs Incubation Period Risk Factors Transmission


Diagnostic Sampling, Testing and Handling Post-mortem Shedding of Virus Following Resolution of Clinical Signs


Environmental Persistence Specific ControlMeasures Biosecurity Issues for Receiving Animals Zoonotic Potential


Definition The upper respiratory disease commonly referred to as strangles is caused by Streptococcus equi or taxonomicallymore correct, Streptococcus equi subsp equi. Less commonly, the bacteriamay affect lymph nodes in the thorax and/or abdomen, causing a syndrome known asmetastatic or bastard strangles.


Comprehensive information is available in the ACVIMConsensus statement, ‘Streptococcus equi Infections in Horses: Guidelines for Treatment, Control and Prevention of Strangles’, Corrine R. Sweeney, John F. Timoney, J. Richard Newton, andMelissa T. Hines, J Vet InternMed 2005;19:123-134. See ACVIM statement


Clinical Signs


• Fever, usually preceding other clinical signs by 24–48 hours • Pharyngitis leading to reluctance to eat and drink. Palpation of the larynxwill often elicit pain


• Soft non-productive cough that is often associatedwith eating • Mucopurulent nasal discharge that can be unilateral or bilateral • Lymphadenopathy +/- abscessation (retropharyngeal and submandibular lymph nodes aremost commonly involved), but any lymph nodemay be involved


• Upper airway stridor secondary to pharyngeal compression by the lymph nodes or neuropraxia causing laryngeal hemiplegia


• Guttural pouch empyema is a frequent sequela to previous lymph node abscessation


• Metastatic infection including: Abdominal abscessation,meningitis, Lymphangitis, Purpura hemorrhagica,myositis, and immunemediated myopathies


Clinical signs are age and immune status related,with older horses typically exhibitingmilder signs of shorter duration. However, every horse is at risk if the dose and frequency of the challenge is significant.


Incubation Period Translocation to themandibular and retropharyngeal lymph nodes occurs within hours of exposurewith clinical signs beginning 3–14 days after exposure. Nasal shedding usually begins 2 to 3 days after the onset of pyrexia.


1 Copyright AAEP – Revised 2017


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