Oh no! We just had a positive giardia diagnosis right before christmas (fun) and still not 100% sure if we are rid off it yet (given the false negatives with these tests, will never know 100%).
Remember cleaning, cleaning, cleaning with giardia :-( and apparently the regular cleaning stuff doesn't kill it, so I got "Halamid" online which seems to be pretty much the only thing that kills it (not sure if it's sold in the U.S. too), used it to clean the floors and also his crate and where ever else he'd like to lay. Also put some in a spray bottle to treat some furniture, although I heard it's better to treat it with heat but that wasn't possible in my MOm's house. Everything I could I dosed off with boiling water (bowls everytime I used them, chuckit, etc.) and washed all blankets, towels, etc. especially those he laid on everyday at highest temperature (90 celcius).
I think that helped in him not picking it up straight away again, but as said, given that it's never 100% that you truly got rid off it or he picked it up outside again, it's a bit frustrating.