Wednesday, May 8, 2013

A Primer on Strangles (Strep Equi)

This is a bacterial disease of horses and other equines.  The incidence has been low but may be increasing.  Traditionally young horses are at greatest risk but with less chance of exposure over the last generations, older horses may not have had the opportunity to develop immunity.  After a natural infection that runs its course, there is a long lasting but not lifetime immunity.   Horses may be chronic carriers.  It is a difficult and expensive procedure to prove that an individual horse is not a carrier.
Prevention: Vaccination may help reduce the frequency and severity of the disease but does not provide a solid immunity in some horses.  There are two types of vaccine, an intranasal modified live (Pinnacle) and  an intramuscular  M protein extract (Strepvaxx II).  Some veterinarians believe that the modified live vaccine can produce disease but that has not been my experience.  The M protein extract may cause swelling and soreness at the injection site.  The disease is primarily transmitted by contact, direct and indirect.  Compared to viral respiratory diseases, it is not transmitted easily by aerosol over distances.   Quarantine sick horses.   Quarantine of new horses in a barn for two to three weeks especially if they have come from a public sale or dealer  is a good idea.   At a show do not let your horse have direct contact with other horses, graze, or drink from a common trough.  At an overnight show stabling is a potential problem.  A true disinfection of the stall is not possible.  A hand garden sprayer with dilute chlorine applied to the inside of the stall might reduce the potential load of bacteria but not help your relationship with neighbors.
Treatment:  If you have a horse with a fever and a copious nasal discharge or enlarged, painful  lymph nodes, seek advice from your vet.
If you want the full story (and want be scared to death about potential but rare complications) here is a link to the American College of Veterinary Internal Medicine Consensus Statement on strangles .   Some of the recommendations may not be applicable to individual situations for financial or practical reasons.