We had strangles in our herd several years ago. It hit just after the first foal of the year was born--his mom was sick, and at less than two weeks of age he came down sick as well. That foal did get treated with a high powered antibiotic; the first horse that came down sick did get some antibiotics, but once we realized that it was strangles we did not treat anyone else other than that first foal. Another pregnant mare came down sick--her symptoms were typical of pneumonia, much like the mare you describe--heavy breathing, snotty nose--this was in late April. The bug ran its course, the mare recovered without drugs, and she foaled a filly on May 31st. (The filly came early, but that is normal for this particular mare). The filly was born healthy, and stayed healthy.
I'd point out to all that strangles does not always produce abcesses--sometimes every horse on the place gets abcesses, sometimes a few will have abcesses and the majority will not have abcesses; symptoms can look like other respiratory infections--pneumonia, rhino, flu--and milder cases will exhibit only a fever, mattery eyes, and/or depression.
Likewise, snotty nose and pneumonia symptoms do not necessarily mean pneumonia. Here we do not treat strangles with antibiotics. If it is pneumonia, though, you better believe it gets treated! It does pay to know what you are dealing with.
