AAEP InfectiousDisease Guidelines: Strangles


dead. Samples collected early in the course of clinical disease (within 48 hours of onset of fever)may yield negative results on culture. If signs are consistent with Strep equi infection, repeat testing atweekly intervals. If several animals are affected, submit single samples fromasmany animals as possible.


The SeMAntibody ELISA cannot differentiate antibodies due to natural infection fromthose induced by vaccination, and is therefore of limited use inmanaging disease outbreaks. Its value is limited to screening animals thatmay react to vaccination, (>1:3200) to support a diagnosis of purpura hemorrhagica or metastatic disease (>1:12,800). It is not ameasure of protection fromdisease or an indication of an active infection.


Post-mortem Strangles is rarely fatal. If a horse dies in acute phase of the disease necropsy findings likelywould relate to upper airway compression due to retropharyngeal or peritracheal abscess formation. Complication of strangles can result in severe disease thatmay lead to euthanasia. Internal abscesses can formin the lung, liver, spleen, kidney, brain,mediastinum, and/ormesentery. These abscesses would be visible on gross necropsy and culture of the abscessmaterial could lead to a definitive diagnosis. Immune-mediated complications include purpura hemorrhagica,myositis, glomerulonephritis, andmyocarditis. Purpura hemorrhagic leads to petechial or ecchymotic hemorrhages onmucous membranes, sclera, and visceral surfaces such as of the lung. Purpura hemorrhagica can result in subcutaneous edemamost commonly involving the head, limbs and trunk. Severe edemamay result in oozing fromthe skin surfaces and sloughing of skin in the affected areas.Myositis results inmuscle infarcts that can be associatedwith purpura hemorrhagica. Significant rhabdomyolysiswith progressive atrophy has been identified inQuarter Horses.


Practitioners performing necropsies in the field are encouraged to contact a veterinary diagnostic laboratory to which they plan to submit samples for further testing such as histopathology and pathogen identification in order to be certain they collect the appropriate samples and handle the samples in a manner that will optimize making a definitive diagnosis. For some situations such as neurologic cases submission of the entire carcass to the diagnostic laboratory for post-mortem examination is recommended due to the time and labor required to performa complete examand collection of samples from the equine CNS.


Shedding of Bacteria Typically, 2–3weeks post-recovery but intermittent sheddingmay occur for Following months to yearswhen bacteria persist in guttural pouches or paranasal sinuses.


Resolution of Clinical Signs In the absence of diagnostic testing to detect chronic shedders, horses should be considered infective for up to 6weeks post resolution of all clinical signs.


Endoscopic examination and sampling (for culture and PCR) of the guttural pouches iswarranted for detection of persistently infected horses.


The onlyway to determine if a horse is still shedding is to test it. 3 Copyright AAEP – Revised 2017


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