How do i know if my dog has lungworm?

I have two dogs. One goes to work everyday with my partner. One stays at home with me. Shep (the one who goes to work) is starting to act different when we return home from our eveing walks. Shep becomes restless like he cant get cool. He pants excessivley even when Roxy (the one that stays at home with me) has stopped and is laid down. Its really starting to worry me. They are both pedigree border collies. They were last vaccinated about a year ago and Roxy has just had puppies?? Just trying to give you as much info as possible. Im going to make a vets appointment first thing monday but is it a serious enough condition that i need to take him to the emergancy vets?? Roxy is almost 4 and shep is 18 months (ish). Sorry to trouble you all on a Friday night!! Thank You & God Bless x