Question about strangles

I need some help. I cannot find the answer to this problem and I have searched the net. My next move is to call the vet but I don't have the time right now. I have a friend who has a mare mini, 5 or 6 years old, that has had strangles 6 or 7 different times. I thought this to be highly unlikely but I can't find anything on it on the net. She presents with a runny nose which then advances into an abcess. It ruptures and heals. Later, she will begin the process over again. This time, she is dropping weight badly. She is pastured with a mini stallion who had them once and has never gotten it again. They were also pastured with a couple of mules than never got the strangles at all. Can any of you help me with some ideas? He is considering putting her down as this has been happening since Spring and she continues to have the problem. He will not sell her like she is but needs to get his place rid of the problem so he can get some cattle in the Spring.