Over time the infection becomes worse with larger numbers of worms infecting the heart and reproducing, making this a downward cycle for your pets health. (caninejournal.com)
Large numbers of worms cause the heart to work harder pumping blood through the clogged arteries. (northcountryvet.com)
In puppies, large numbers of worms usually must be present before eggs are shed into the stool. (thedrakecenter.com)