I use Woolite and depending on what kind of pad, either load it into the front loader washer and put it in gentle cycle or soak it in my bath tub and THEN put it in the front loader washer for a rinse and spin cycle. Then hang to air dry, do NOT put in a dryer, and only cold water wash, wool will shrink, even wool felt!
Do NOT use bleach on Wool, it breaks the fibers down and causes Wool to disinigrate faster. Washing good in Woolite should take care of any 'nasties' but if you want to feel 'extra' safe, you can add some of the Equess Blanket Wash with the Woolite (a 50/50 mix seems to work well!).