Does anyone know how to get rid of the smell of mice in a van?

My van was stored, covered, outside all winter.  When I opened for the
summer, the rodent smell was awful.  Mouse turds everywhere, and several
nests in the storage closets.

I've tried washing completely and airing out, but no luck yet.  It still
smells like rodent droppings. YUCK.

Does anyone have any experience getting this smell out?  My wife won't camp
the way is smells now and honestly I can't blame her.

Thanks in Advance,

Scott Curtis