Heartworm – So easy to prevent…

Tue Nov 14, 2023


Why you should protect your pet from the spreading threat of Heartworm

It’s that time again: your pet is due for her annual wellness exam. You have choices to make about vaccines, screening tests, and preventive care recommendations, and you may feel unsure about whether everything on the list is really necessary. For instance, you may question whether testing your pet for heartworm and putting her on a preventive makes sense, given that you haven’t heard much about the disease occurring in our area.

Naturally, there is good news and bad news. The bad news first: Although the incidence of heartworm is currently much higher in southern and mid-Atlantic states than Connecticut, it’s spreading and becoming more common in our area. Heartworm is a serious, potentially fatal disease spread by mosquitoes that causes permanent damage to the heart, lungs, and arteries.

The good news is that heartworm disease is easily prevented, and the more aggressive we are about preventing heartworm, the less opportunity it will have to spread.


Lilly’s Story

Like many dogs rescued from shelters, Lilly’s story began in a southern state where mosquitoes thrive due to the warm, humid climate. Lilly was born into unfortunate circumstances, and her first 9 months saw poor nutrition and no preventive vet care other than the mandatory rabies vaccine. Eventually, Lilly was picked up by a dog warden and taken to a local dog pound, where her fate was even more uncertain.

Luckily for Lilly, a caring human adopted her from the dog pound and transported her to Connecticut where she could join other pets in search of a forever home. Lilly finally received some long-overdue care. She was dewormed, neutered, and brought up-to-date on all the recommended vaccines. Young and friendly, she was soon adopted by a family and became the apple of their eye. Unbeknownst to all, however, was the fact that, during her time in Alabama, Lilly had been bitten by mosquitoes that carried heartworm.

Her symptoms were mild at first – intermittent coughing and periods of lethargy – but they gradually became more severe. Lilly was tested and found to be positive for heartworm. This came as a shock to her human family. When they adopted Lilly she seemed perfectly healthy! To their credit, they committed to treating Lilly for the disease, and after many months she was finally rid of the heartworms that would have made her extremely sick and cut her life short. Now Lilly gets a monthly heartworm preventive that looks and tastes like a yummy treat, and her family will never again have to worry about heartworm.

Lilly’s story does not end here. Although she recovered with minimal long-term consequences, she brought the heartworm parasite with her to Connecticut where it could spread through mosquitos to other dogs, and cats as well.

Does this mean we should stop adopting rescued dogs? Of course not. Lilly’s story is just one example of how easily heartworm can impact a pet, how easily it can move from one region to another, and how important it is to focus on prevention.

Image courtesy of the American Heartworm Society


Prevention is the “no-brainer” option

The old saying that “an ounce of prevention is worth a pound of cure” was never more apt. Heartworm has been diagnosed in all 50 states. No one wants to be the pet owner who gets the news that their pet has heartworm disease, especially if they could have taken simple steps to prevent it.

The American Heartworm Society recommends that you “think 12:”

  • Get your pet tested every 12 months for heartworm, and
  • Give your pet heartworm preventive 12 months a year.

Tolland Veterinary Hospital recommends testing your dog or cat once a year at their annual wellness exam. This same blood test also screens for common tick-borne infections, Lyme, Ehrlichia and Anaplasma, so you can use it to help your pet stay ahead of these threats, as well.

Preventive treatment is easy for both cats and dogs. It comes in the form of a tasty, chewable cube or a liquid that’s applied to the skin. Not only does this user-friendly medicine prevent heartworm, it also prevents roundworm and hookworm, two common intestinal parasites that can also make your pet sick.

If your puppy is under 7 months old, she can begin heartworm prevention without first taking a test, but she should be tested 6 months after starting the preventive, then annually from then on.

If your dog is older than 7 months and was never on a preventive, he needs to be tested before starting a preventive. Once on the preventive, he should be tested annually going forward.


Heartworm is spreading our way

If you’re still on the fence about whether to opt for testing and prevention, consider the fact that heartworm disease is spreading. The more infected animals, the more opportunity for mosquitoes to transmit the disease. It’s a vicious cycle that favors the parasite.

The American Veterinary Medical Association notes that Massachusetts and Connecticut, which have been among states with “historically low heartworm rates,” saw “unexpected increases” in heartworm incidence during the most recent data survey released in 2023.

Check out these American Heartworm Society Incidence maps to see how heartworm disease has been spreading over recent years:


Why is heartworm spreading? The short answer: mosquitoes are highly adaptable and live everywhere, even indoors over the winter. And pets move into and out of areas that have higher rates of infection, whether due to recreational travel or relocation for adoption.

For example, the American Heartworm society reports that at least 60 percent of the dogs evacuated from Hurricane Katrina were heartworm-positive. These dogs were adopted and sent all over the United States. And that was just one of many such disasters impacting pets. Ongoing pet homelessness is another major factor contributing to the spread of heartworm. According to the ASPCA, 6.3 million pets enter shelters each year, many of whom are untested with no access to prevention.

There are also just simply lots and lots of heartworm hosts available to mosquitoes – 2/3 of US households have pets, including more than 100 million dogs and cats. More than 1 in 4 US pet owners don’t take their pets for annual wellness exams where they could be tested and offered preventive care, and many cat owners are not aware of the risk of heartworm and so do not ever test their cats.


Dogs are especially vulnerable

For dog owners, taking steps to prevent the devastating effects of heartworm is especially important. This is because dogs are an ideal heartworm host. Heartworm larvae transmitted to a dog by a mosquito are able to complete their entire life cycle while living in that dog. The larvae mature into adult worms, mate, and produce offspring, which can then be transmitted by mosquitoes to additional host victims, spreading the disease. A dog can be host to several hundred heartworms at a time.

Although cats can also become infected and get extremely sick, they are not ideal hosts for heartworms, so the disease doesn’t affect them the same way it affects dogs. It’s far less common for heartworms to reach the adult stage in cats, so the number of adult worms found in a cat is usually very low if there are any at all.  But even immature heartworms can cause serious illness and death in cats. Many cats die as a result of heartworm disease, and those that survive often experience long-term health complications.

For information about symptoms, testing, treatment, incidence maps, and more, visit the American Heartworm Society.

For a deeper dive, watch this Video provided by the American Heartworm Society that illustrates the life cycle of the heartworm parasite and how it causes disease in our pets.


Here are some fast facts about heartworm disease:

  • Heartworm impacts dogs, primarily, but also cats and ferrets.
  • Coyotes and foxes can also have heartworm disease, which contributes to its spread.
  • It takes 6 months for microscopic larvae transmitted by mosquitoes to grow into adult worms.
  • Heartworm disease is caused by foot-long worms (heartworms) that live in the heart, lungs and associated blood vessels of affected pets.
  • Adult heartworms can live up to 7 years in a host dog.
  • Pets don’t become “immune” once infected; they can continue to be infected with each mosquito season.
  • Humans cannot get heartworm disease directly from their pets, but in rare cases they can get heartworm from an infected mosquito.


What if my pet has heartworm?

Heartworm disease can be treated, but it’s a much better strategy to prevent the disease in the first place. Treatment is a long and costly process, easily running into the thousands.

If caught in the early stages, most infected dogs can be successfully treated. But it is an expensive, lengthy, multi-step process. Once the diagnosis is confirmed, exercise must be restricted to minimize damage to the heart and lungs. It can take several months to stabilize the dog’s condition prior to beginning a treatment protocol set up by your veterinarian. Then about 9 months following treatment, the dog must be tested to ensure that all of the heartworms have been eliminated. Once treatment has been deemed successful, the dog will need to start preventive medication and stay on it forever.

If your cat develops heartworm, the treatment plan is very different – in fact, it’s really more of a disease management plan. You can confirm the diagnosis, but there is no medication to eliminate the heartworm parasites like there is for dogs. You can monitor your cat’s condition with X-ray, try to control inflammation with a steroid medication, and support your cat with IV fluids, hospitalization, antibiotics, or even try to have the worms surgically removed. You can also continue to give your cat a monthly preventive medication to avoid additional infections.


What’s the take-away?

Heartworm disease is spreading in our area, and it’s a serious threat to your pet’s health. Treatment is possible but difficult, so prevention is by far the best option. As your partner in your pet’s health and well-being, Tolland Veterinary Hospital strongly recommends making annual heartworm testing and year-round prevention part of every dog and cat’s wellness regimen.


Connect with us!

Do you have questions about Heartworm or how to protect your pet from infection?

Get in touch with us by clicking here: https://tollandvethospital.com/contact/

and we’ll do our best to provide the information you’re looking for.




Keep the Worms Out of Your Pet’s Heart! The Facts about Heartworm Disease | FDA



Call Us Text Us