I don't know the answer to your question but I just wanted to add that the vets told me that the strangles vaccine is only worth the money if the whole yard has the vaccine done... I think I will see if people want to do it next year (pregnant mares cannot have it done) as to me it is worth the money just to stop the horrible disease spreading
My vet doesnt recommend it because of cost, reaction to vaccine, effectiveness etc etc. Advised isolation of new horses on a yard, cleanliness and caution at shows i.e. nose to nose contact, take you own water and buckets etc. Said this was much more effective.