Removing parvo completely from the yard can be challenging for obvious reasons. Several vets say it is close to impossible, unfortunately. You can reduce numbers by removing any feces and using a diluted bleach solution (one part bleach to 30 parts of water) to clean hard surfaces. Dirt and grass can be sprayed with the diluted bleach solution, however, it's important to understand that bleach will kill grass and that parvo may still be present in the yard. Shoes should be disinfected too after walking in the yard.