You're welcome.

Other than the vaccines I mentioned and quarantine, the most effective
measure against parvovirus is disinfection since the virus remains infective
in the environment for ~ 1 year or more and can be carried around on
clothes, shoes and hands.  Other than the bleach solution I mentioned, you
might want to mention Virkon S to the shelter manager- it completely
inactivates feline and canine parvovirus and just about every other feline
virus and bacteria and fungus- including ringworm (Feline Calicivirus.
Feline Herpes Virus [Feline Rhinotracheitis Virus], Feline Infectious
Peritonitis Virus [Feline Coronavirus], Feline Panleukopenia Virus [Feline
Parvovirus]. Its completely safe to use on cat cages- its not a quat or
phenol and has no odor.  Costs about $55/10 lbs.  At a 1% solution (1:100),
1.3 oz. makes a gallon- 10 lbs makes about 123 gallons.  In FLA, you can get
it 1-877-996-2635.

The most important thing to remember is never put a new cat in a cage that
hasn't been disinfected or let her use litterboxes or bowls that haven't
been disinfected.  Many cats can carry the virus, shed it, and extinguish it
without ever developing symptoms.
Given your shelter's present situation, I'd seriously consider testing the
cats for parvovirus with the CITE Canine Parvovirus Snap Test Kit (Idexx
Labs). The Canine Snap works just as effectively with cat poop as dog poop
for detecting parvo and only takes 10 minutes- no blood draw is required so
if you can tie your own shoe laces you can run the tests yourselves
in-house- that's how simple they are.  The kits run about $10- (vets charge
$30-$45).

Good luck,

Phil