No to torch. If you really want to clean up as much of the parasites and bacteria as possible without sterilizing your soil with chemicals then churn it as deep as you can several times over a week or more. Exposure to UV light, sunshine, and air will kill 99% of the harmful crud without damaging the good stuff in your soil. Treat it with sweet lime or dolomite lime which is great for your birds and changes the PH of your soil, another whammee to harmful stuff.
The healthier you make your soil the least likely anything nasty will take hold. I am proud to say when I turn the earth in my run it smells like soil and the earth worms are both HUGE and in great numbers so my soil is thriving. My birds love it when I come out with a pitchfork to do any churning.