One of the more common questions we receive in the veterinary clinic is whether dogs should be on year-round heartworm prevention, even in the winter and colder months. Over 20 years ago I was taught in veterinary school that the average ambient temperature had to be 65 degrees or higher for 30 days in a row for mosquitoes to become infectious and transmit heartworms to dogs. In most areas of the country this transmission season was believed to be 3 to 5 months.
However, in recent years with concerns of global warming and milder winters, veterinary parasitologists have found that it is possible for mosquitoes to carry heartworms even in milder winter months. Because of this and the fact that many people travel with pets back and forth to warmer areas of the country, most veterinarians and the American Veterinary Heartworm Society now recommend year-round heartworm prevention for dogs in most areas of the country. An added benefit of most monthly heartworm preventatives including Heartgard and Iverhart Max is that most of these preventatives also treat and control many intestinal parasites, which can also be a problem any time of year.
If your pet is not on heartworm preventative medication, it is strongly recommended that you have a blood test performed on your pet at the veterinarian’s office so that monthly preventative can be started to prevent this potentially serious disease. For clients interested in more holistic heartworm prevention options, herbal products such as black walnut and quassia bark can be considered. In these situations, a consultation with a holistic veterinarian is recommended (i.e. www.doctordym.com) as many alternative products have not been proven effective in clinical studies, so that often their use is empiric and based on clinical experience.