Does My Dog Need Heartworm Prevention in the Winter?

Filed under Dr. Dym's Vet Blog
Wondering if your dog needs heartworm prevention in the winter?

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. as many alternative products have not been proven effective in clinical studies, so that often their use is empiric and based on clinical experience.

Read Related Posts on PetMeds® Blog:

  1. PetMeds® Resistance to Heartworm Medication?
  2. PetMeds®: Heartworms in Dogs and Cats
  3. PetMeds® Missing Heartworm Pet meds Dosage
  4. How Often Does My Pet Need a Heartworm Test?
  5. Shortage of Immiticide


  1. fati
    Posted December 18, 2012 at 5:16 am | Permalink

    The Right Food For Your Dog here:


  2. maria c alfeo
    Posted April 7, 2013 at 1:52 pm | Permalink

    my dog dozer a pitt 3 yrs old has heart worm, his skin is very dry, and falling out all the time, when he drinks his water to fast and eats to fast he throws up all this flem with his food, some times he gags or lately when i walk him he sort of gasps for air , i thought because he’s strong and he pulls me to his destination to get to where he wants to walk too, , i can’t offord meds for him, what can i do, ppl say that he’s suffering, but yet he is so playfull, he is a very good dog, can u help me ?


    Dr. Michael Dym, VMD veterinarian Reply:

    Should to vet about heartworm treatment with drug immitide. If this not possible, then consider monthly heartguard or iverhart which can kill heartworms with continuous 1-2 year use. Also ask vet about 30 day prednisone and doxycycline drug trials which can help with infections and secondary lung inflammations.


  3. Posted July 20, 2013 at 9:33 pm | Permalink

    I have a 5lb. yorkie that used to get interceptor 1x month & K9 Advantix II for flea, tick & mosquito repellent 1x month. Now Interceptor is no longer made so I want to continue the K9 Advantixx II & Sentinel. My Question is can they be used together since Sentinel also is for fleas & heartworm but not for mosquitos whick are prevalent in the area that I live. I don’t want them biting my dog. If Sentinel shouldn’t be used with the K9 what about using inverhart max for heartworm and she weights 5lbs. the inverhart lowest dose is for 6 to 12lb dogs heartguard is up to 25lb. I don’t want her to have too much meds which might make her week. I have asked my vet and I get no straight answer they just keep pushing the heartguard. Please can you help me make the right choice.


    Dr. Michael Dym, VMD veterinarian Reply:

    I dont think a problem using the Sentinel and advantix.


  4. Posted June 4, 2014 at 9:49 am | Permalink

    hey i suggest you this useful post

    has a good info to dog heart disease symptoms and treatment!


  5. Jaye Munger
    Posted September 29, 2014 at 2:00 am | Permalink

    I have given my Shepherd Gracie, Trifexsis..but she seems to have developed itchy, dry skin after her second dose. She is a long coated girl, and I brush her EVERY DAY for at least 30 mins. Her coat is silky and shiny, and she eats top quality food w/out additives, and spends a lot of time out in the fresh air. Can you recommend another product for flea and Heartworm control ?
    Perhaps I should use a product for each, rather than the pill.
    Thanks, Jaye


    Dr. Michael Dym, VMD veterinarian Reply:

    I would go with topical revolution which does both fleas and heart worms, and has only one chemical in it.


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