AAEP InfectiousDisease Guidelines: Strangles


Environmental S equi was shown to survive less than 24 hourswhen cultured onto surfaces Persistence exposed to direct sunlight. After aggressive cleaning and disinfection, surfaces should be allowed to dry thoroughly. Special attention should be paid to community surfaces such aswater, hay, and feed containers. Disinfectants


There is no evidence for prolonged survival of S equi on pastures. However, it is frequently recommended to allowthe pastures enough “rest” time to allowfor the bacteria to denature. That interval is likely dependent on the environmental moisture, heat, and sunlight.


Specific Control Biosecurity Guidelines Measures


In the face of an outbreak, the risk of personnel contaminationmust be balanced against the value of tracking rectal temperatures. Twice daily monitoring is recommended and any horse showing pyrexia should be isolated immediately. There is a lag between the initial pyrexia and nasal shedding of bacteria. Leaving hand sanitizer at each stall is useful to encourage staff to disinfect their hands and be cognizant of the contagious nature of S equi. Making certain that caretakers are also not contaminatingwater hose handles when filling buckets is important.


A detailed protocol for establishing a tiered risk systemof handling horses during an outbreak is available in the ACVIMproceedings.


Biosecurity Issues Limiting exposure is the bestmethod of prevention of an outbreak on a farm. for Receiving Quarantine of newarrivals for should also include screening for S equi. Isolation Animals withmonitoring of rectal temp and endoscopy of the guttural pouchmay help to identify infected and sub-clinical shedding individuals.


On a farmcurrentlymanaging an outbreak. Incoming animals should be quarantined in a “clean” area and screened for infection and sub-clinical status. If the farmis not instituting risk-based tiermanagement, turning “clean” horses out into infected herds or pastures is likely to perpetuate the outbreak.


Vaccination - Currently considered to be a risk-based vaccine according to the AAEP Guidelines for Vaccination of Horses While itmay be advisable to recommend vaccination, specific vaccination decisions should remain in the purviewof the attending veterinarian.


Titers can bemeasured before vaccinationwith the goal to identify individuals at risk of developing complications fromvaccination. Titers against SeMdo not indicate protection. Vaccinatingwithmodified live bacteria can lead to confusionwhen instituting testing to clear horses. Testing by PCRmay cause false positives up to 30 days after vaccinating. Positive vaccine culturesmay occur for up to 36 hours post IN vaccine.


(Note: Veterinarians should determine risk factors associated with this vaccination.)


4 Copyright AAEP – Revised 2017


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