Prevention??  Healthy colonies.  I doubt wax moths killed all 8 of your
colony--they were probably dead or nearly so and wax moths just took
over.   Wax moths are in most colonies during most of the growing
season--they lay eggs, the eggs hatch, and the bees haul the larvae out
of the hive.  When your colonies die out, abscond,  or otherwise take a
powder, there is no naturalo control of wax moths so they do their dirty
work.    The same goes if take remove combs from a colony--was moth
eggs and larvae are on them, so with no bees present, the eggs and
larvae go to town.   For this reason, "storing"  equipment on small or
weak colonies isn't a good idea--esp. if the combs are nice, dark old
combs that have had lots of brood reared in them.  One way to reduce
wax moth damage on combs used for honey supers is to use combs that
have not been used for brood rearing--these are of very little interest to
wax moths.
 
For this  stored equipment goes, fumigate, freeze it (if you have access
to a walk-in freezer or don't have too much stuff to freeze) for 24 hours,
or store equipment in an open, light environment.  Wax moths love the
dark, hate light.