How to deal with a person with Alzheimer's, Demetia, and Organic brain disorder

I live with mom and my stepfater who is the one who is sick. He urinate s and deficates on himself and speads it all over the house. He playswith it with his hands and spreads it when he steps on it and with his hads when he plays with it. He infects the whole house especially the kitchen, on the counters, on the dishes, fredidare, stove, walls, sick... well you name it. It is discusting! everything has to be sterilized and we have to watch where we step and where we put our hands. My mom is frustrate as well as myself but see refuse to put him in a nersing home or anywhere else. I don't want to be her but I can't leave my mom alone with him. He has four other children that seems to not care or do anything for him. They all live up north. Any suggestions would be appreciated, please, thanks.