Is it cotton or a blend, or can you tell? Assuming that it is in fairly good shape and is not going to rot away, I would probably wash it in cold water on a gentle cycle in the machine, pretreating stains with whatever seems the most appropriate product -- shout, borax, oxyclean? and then using vinegar in the rinse to help with the odor. I would line dry, preferably in the sun, and recheck for stains and odor. It may take several washings.
RST