You might want to check out on the Frugal Life site https://www.thefrugallife.com/pets.html
If its in the dirt, I would replace the dirt by digging up the infected dirt. If its on the wall, I would seal the spot with Kilz or something similar or use the product I reference below. Then paint over it. The link I referenced above has some good ways to limit cats coming to your property.
A product specific to removing pet urine ordors can be found at http://www.healthypetcorner.com/FRR/petforce.html
This product has been used in kennels, barns and stalls effectively.
Hope that helps.
Randal – Editor of The Frugal Life News