Has anyone had a giardia case? What did you do?

I recently had a dog with diarrhea and, unfortunately, the problem was getting worst with time (more loose, but his behavior and appetite did not change). I took the pup to the vet and the diagnosis was giardia. Of course, the water I offer to the doggies is potable and clean (no ponds or visits to lakes or dog parks), so probably the source of the pathogen was an asymptomatic dog or that same dog that started to show the symptoms when under my care. My major concern is that now my yard is "contaminated" and any vulnerable dog may get sick. How should I handle this? Is spring/summer time and the dogs play outside in the yard almost all day long. I just can't lock them inside. Besides, the pathogen is very resistant and won't just disappear in a couple of days (can be there for months or even forever). Have you had this problem? What did you do? Any advice? Thanks!