EXTREME PET ODOR!! Please help!

[Jake Oreskovich]

Hello BP members. Recently I purchased a new rental that was distressed to say the least. I purchased the property from a landlord who was just burned out. His tenant went on a drug/drinking binge and he and locked himself as well several dogs and cats in the home. In the process of me evicting the tenant, he was thrown in jail. Needless to say his dogs and cats were still locked in the home. By the time animal control was able to remove the animals, we found that he had locked the animals in the basement and they had been urinating and pooping throughout the basement and other stray cats got into the home. 

Once I got everything out the smell was horrendous. I pulled ALL of the flooring, ALL of the subfloors etc... I had a crew go in and deep clean every piece of concrete in the basement with bleach and I sprayed every square inch of the wood (floor joists, window wells, etc...) that I could find with KILLZ before painting. What it seemed to do was mask the odor slightly but then it came right back about a month later. 

I've scheduled a vent cleaning company to come out and try to clean the vents and the furnace in the event the animals urinated in the duct work. Starting to get a little discouraged as I've exhausted everything I could think of. Has anyone ever dealt with anything like this or does anyone have any ideas. I've been a landlord, flipper, investor for over 10 years and I've never seen anything like this. I even cleaned the house with chemicals that I purchased from a commercial janitorial company that are supposedly used to clean bio-hazard (death sites)........still didn't do the trick. PLEASE HELP!!!