re: Update in OP; Treating young lab for heart worms

You can try black walnut hull and wormwood tincture. We've been doing that for a stray we took in about 4 years ago that tested positive. I get it from the vitamine shoppe and put a few drops in his food. It's not going to eliminate them, but combined with a preventative like heartguard, I believe it helps a lot in keeping them from getting worse. It certainly has helped with his symptoms, he used to cough and wheeze back when we first got him