Does Your Pet Need Heartworm Preventative During Cold Winter Months?

Because heartworm disease can only be transmitted through the bite of a mosquito, many pet owners opt to discontinue heartworm preventative once the weather turns cold. We were among those pet owners. We did our research and weighed the options. Because we live in New York State we decided that it was safe to discontinue giving a heartworm preventative to our last dog, Lucy, during the cold winter months. We believed that exposing her body year-round to the toxins in the preventative medication was a bigger health threat.

A blood test was required in the spring before we put her back on a preventative, and to our horror, she tested positive for heartworm.

The treatment was long and costly but it wasn’t the cost that bothered us. We felt so guilty that she had to go through this treatment that required weeks of confinement. She was an active dog used to taking daily walks and weekend hikes. The heartworm treatment required that she stay as quiet as possible while the worms died off. That meant short walks just long enough for her to do her business and then back to the confinement of her crate. It was so hard on her. We were lucky that she made a full recovery and lived to the ripe old age of 15.

LucyLucy recovered from heartworm treatment and lived to the ripe old age of 15.

How Significant is Your Pet’s Risk for Heartworm Infection?

According to the American Veterinary Medical Association, heartworm is a preventable, but serious and potentially fatal, parasite that primarily infects dogs, cats and ferrets. A 2016 heartworm prevalence map published by the Companion Animal Parasite Council (CAPC), showed that 1 out of every 76 dogs in the U.S. tests positive for heartworm. The CAPC study shows that 13 states are considered high risk for heartworm infection. These states are primarily in the southeast, where rising temperatures and high humidity during the warmer months of the year provide an ideal environment for mosquitoes to thrive.

mosquitoe Image courtesy of Thinkstock

Experts at the American Heartworm Society (AHS) believe that many factors must be considered even if you think that heartworms are not a problem in your area. According to the AHS:

Heartworms have been found in all 50 states, although certain areas have a higher risk of heartworm than others. Some very high-risk areas include large regions, such as near the Atlantic and Gulf coasts, and along river tributaries. Most states have “hot spots” where the heartworm infection rate is very high compared with other areas in the same state. Factors affecting the level of risk of heartworm infection include the climate (temperature, humidity), the species of mosquitoes in the area, presence of mosquito breeding areas, and presence of animal “reservoirs” (such as infected dogs, foxes or coyotes).

Experts at the AHS believe that the risk factors are impossible to predict and for that reason, they recommend that pets are tested every 12 months and given heartworm preventative year-round.  

Not All Veterinarians Follow These Guidelines

Instead of focusing on the scary nature of the disease that occurs in a small percentage of dogs, many holistic veterinarians believe that decisions on whether or not to use year-round heartworm preventative should be based on where a client lives. Besides exposing your pet’s body to chemical pesticides with the potential for toxicity, heartworm preventatives are not actually preventatives according to an article titled “10 Things You Didn’t Know About Heartworm” that published in Dogs Naturally magazine. According to the article:

The so-called heartworm preventive drugs don’t prevent your dog from being infected with heartworms. Instead, they work by killing heartworm larvae that may already be in your dog’s body. So they’re actually treatment drugs, not preventives. And if your dog hasn’t been infected, you’re treating her for something she doesn’t even have.

This article also refers to the fact that the AHS is being sponsored by big pharmaceutical companies. The link the author makes, of course, is that these companies have a vested interest in giving pet owners as much information as possible to convince them to buy drugs to protect their pets.

In the end, it’s up to individual pet owners to make the decision for their pets. Our experience with Lucy left its mark. While we still hate exposing our current dogs Jason and Bella to toxic chemicals, we do keep them on a year-round heartworm preventative. We have discussed this decision with our veterinarian and asked if there are any reliable holistic alternatives. She doesn’t believe so and for now, we are going with her recommendation.


The American Heartworm Society offers detailed information on heartworm disease and how to protect your pet.

The American Holistic Veterinary Medical Association offers a list of holistic veterinarians that may be open to using alternative methods of preventing heartworm disease.


Photo Credit: Thinkstock


HEIKKI Ryesterday


Sue H
Sue H5 days ago

Helpful information, thanks.

Leo C
Leo C5 days ago

Thank you for sharing!

Camilla V
Camilla Vaga5 days ago


Virginia Miller
Virginia Miller6 days ago

Thanks for the info

Maureen G
Maureen G6 days ago

It is worthwhile reading as much s possible about heartworm so you can make an informed decision.

Connie O
Connie O7 days ago

Thank you for the info.

Muff-Anne York-Haley


Stephanie s
Stephanie s7 days ago

Thank you

Winn A
Winn A7 days ago