The number of dogs registered per state.

A friend and I were just talking about the various diseases his new GSD
can aquire. We were able to find hard numbers of stuff like rabies and
heartworms in the area but have no "total" to compare it to. For
example, 137 cases of rabies in an area populated by 150 dogs is a
staggering number when compared to 137 cases in an area of 20,000 dogs.
Does anyone know how to find this number? I know registration is
optional but since we are taxed on our rabies tag I figured I could get
a decent number if I knew how many dogs were vaccinated. Any ideas?

- Phil