Entomologists from U. C. Berkley came to Placerville to catch mosquitoes for their studies. We have a lot of heartworms here. Unprotected outdoor dogs will probably catch heartworms. Indoor dogs going outside in the morning and evening will probably catch heartworms. If you think your dog's long hair will protect him, forget it.
Statistics show that long hair offers no protection whatever.
There are no symptoms at all until the disease is very advanced. Waiting for symptoms to develop and then treating is not a realistic alternative to prevention. We currently recommend a good-tasting monthly product called Interceptor because it is entirely internal and also controls the most important intestinal worms. In cold climates, prevention medication is not necessary in the wintertime. In Placerville, we have mosquitoes year 'round, and although we could theoretically skip the medication when it is sufficiently frigid, the weather is different every year.