A prevention program should be started at 6 to 8 weeks of age in endemic areas, or as soon thereafter as climate conditions dictate. In the Deep South, where mosquitoes are a year-round problem, dogs should be kept on preventive drugs all year long. Consult your Pet Med store or your veterinarian.
Heartworm Preventives: Pet Med online store has all of these:
Heartgard is given once a month. This drug acts on the L(4) larvae. Dogs do not have to be heartworm-free to initiate therapy; dogs infected for as long as two months before treatment will not develop heartworms. Heartgard is marketed in chewable tablets of different sizes, depending on the weight of the dog.
Heartgard Plus is a popular chewable tablet taht combines ivermectin with pyrantel pamoate. This combination prevents heartworms, and also controls roundworms and hookworms.
Interceptor (milbemycin oxime) is another administered once-a-month heartworm preventive that also acts on the L(4) larvae. This drug also controls hookworms, roundworms, and whipworms. It is safer to use on Collies and Collie crosses.
Selamectin (Revolution) is a once-a-month liquid heartworm preventive applied to the skin of the dog's neck between the shoulder blades. It is available from your veterinarin in premeasured doses based on the dog's size and age. A principal advantage of selamectin is that it also controls adult fleas and prevents flea eggs from hatching for one month.