Our old vet had a model of an infested heart - gross!!! He also said it was prevelent inour area. Both are on heartworm preventative, used to use Frontline, now using Interceptor. Just switched to K9 Advantex because of the mosquito repelling factor - those are pretty bad around here after our rainy spring. My huskies live outdoors, so there is reason to use it. If they stayed indoors all the time, I might think about discontinuing its use. Also have planted several mosquito-repellent bushes in their yard. Never have seen fleas on them. Ticks were bad in IL, Star had one that caused a hot spot. That's when I started using Frontline.