Maybe, maybe not. Although actually having the disease and being infected with the Strangles bacteria is the best way to produce a high antibody response, the immunity afforded to your horse by natural infection is typically only high for a few years. After 2-3 years the antibodies that the body had previously produced against the Strangles bacteria are likely waning.
However, every horse has a different immune system and some horses do not follow this rule. Some horses may retain that very high immunity for many years after infection. The only way to be completely sure about this is to perform a simple blood test to measure the antibody level. If the level is low, then it may be necessary to begin vaccinating your horse again. If it is high, then your horse’s immunity is still sufficient and vaccination is not needed. If you are aware that your horse has previously been infected with strangles bacteria you should always bring this to your veterinarian’s attention prior to vaccination.
