This is the best website to getup to date info on the prevalence of different parasites in the united states. The information is based on data from the “center for disease control”, the CDC. Future forecasts combine this data and weather reports that affect the population of parasites. “Look-up” Map are available for each parasite and by species. Also the many informative articles  can help you determine how to handle parasite control for your pet. This is the information used by Vet.s to make recommendations to their clients.

http://www.capcvet.org/parasite-prevalence-maps/