Bastard Strangles is fairly uncommon, thankfully. The symptoms are similar to regular Strangles however it become Bastard Strangles when the bacteria moves from the lymph nodes in the throat to other parts of the horse's body where it can create abscesses. Depending on where these abscesses occur dictate whether it will be fatal or not.
Regular Strangles is generally not a huge deal - a bit worrying for the owner for a month or two and unpleasant for the horse, however he generally makes a fully recovery and in about 75% of cases, once the Strangles has gone, the horse becomes immune to the condition.
Bastard Strangles should not be taken lightly - it is very dangerous and often fatal!