Caring Hands, Compassionate Hearts.


Myths About Heartworms

April is Heartworm Awareness Month, so we’d like to take some time to address some misconceptions that we hear from pet owners regarding heartworm disease and prevention.

MYTH | Heartworms are a scam made up by the veterinary industry to make more money.

Unfortunately, heartworms are a very real threat to the health of our beloved pets. Transmitted by mosquitoes, these parasites develop from microscopic larvae into worms up to a foot long. They live in the circulatory system and cause damage to the heart, lungs and blood vessels. Untreated, a dog may become the host for several hundred of these worms. Physical blockage of the heart and blood vessels can occur, resulting in death. The worms sometimes migrate outside of the circulatory system, causing direct damage to other organs. While there is a drug to treat heartworms in dogs, there is nothing that can reverse the damage that has been caused by their presence. Permanent scarring of organs can continue to affect the dog’s health and shorten its life.

MYTH | My dog is not around other dogs (and/or I have a fenced in yard), so he doesn’t need heartworm prevention.

Heartworms are not directly transmitted from dog to dog (or cat to cat). Mosquitoes are an intermediate host and serve as the method of infection. It only takes one bite by an infected mosquito to transmit heartworms to your dog or cat. And the mosquito becomes infected by biting a carrier animal – an infected dog, cat, ferret, fox, coyote, even a sea lion – so the source pool is quite large. Once established in a host, heartworms can survive for several years, so each year there is a greater number of infected animals in a particular area.

MYTH | Cats are not at risk for heartworm.

While cats are not a natural host for the heartworm, they can still be infected. In fact, this makes it more difficult to detect their presence. Once a cat is infected, only a few worms may be able to mature to adulthood if at all. However, even immature worms cause very real damage inside the cat. They often migrate through the body, especially the lungs. Affected cats often exhibit respiratory related signs, such as coughing and asthma-like attacks. These cats may be diagnosed with HARD – Heartworm Associated Respiratory Disease. Sadly, many cats with heartworms show no signs at all and simply collapse in sudden death. There is currently no treatment available for heartworms in cats.

MYTH | My pet stays indoors so I do not need to give him/her heartworm prevention.

As explained above, it is the mosquito that transmits heartworms. These tiny insects can be very aggressive and opportunistic in taking up residence and finding sources to feed on. The inside of your home is a paradise for mosquitoes – climate controlled, sources of water, and hosts to bite. They can enter through tiny cracks in windows or vents, or simply follow you as you enter through the door.

MYTH | I have my yard sprayed for mosquitoes/we have lots of frogs in the yard, so my pets are protected.

It is great to have a method of controlling mosquitoes for the sake of you and your family’s health and comfort. However, since we aren’t able to create a mosquito blocking force field around an area, there is no way to keep your environment totally pest free. Knowing that it only takes one bite from one infected mosquito to infect your pet, do you really want to take that risk?

MYTH | My dog was given heartworm prevention during his first visit to the vet, so he is protected for life.

It would be wonderful if there was a product that could provide life-long prevention. However, the majority of currently available preventatives must be given every 30 days. (There is an injectable product that works for 6 months). These preventatives work by eliminating any immature heartworms that may be present in your pet at the time they are given. So in a scenario where you give your pet his prevention on the first of the month, the dose given on April 1st attacks any heartworm larvae that have been introduced since the previous dose on March 1st.
These medications are unable to eliminate any worms that have developed into the adult stage. If they are not given every 30 days, this increases the chances that there will be larvae that make it to the adult stage.

MYTH | I only need to give heartworm prevention during warm weather months.

Mosquitoes can be present in an area year-round. There are many different species, each with differing ranges of cold tolerance. Studies have also shown that some species can successfully survive over the winter completely indoors. My personal experience is that I seem to get mosquitoes in my house every December.
According to the University of Florida, sixteen species of mosquitoes have been identified as natural hosts of D. immitis (dog heartworm) in the United States east of the Mississippi River.
To properly protect your pet, give heartworm prevention every month, year-round.

MYTH | I give my pet heartworm prevention every month. He does not need to be tested for heartworms.

Even with monthly preventative, there is still a chance your pet could become infected. Your dog may spit out his pill when you are not looking, or rub off a topical medication. There may be worms that survive the exposure to the preventative and go on to become adults. A veterinarian that I used to work with liked to compare heartworm prevention to birth control – neither are guaranteed 100% effective.

Heartworm disease is progressive, and the sooner an infected dog is treated, the better the chances for a successful treatment and healthier life post-treatment. It is key to detect the presence of heartworms sooner versus later.

Additionally, the heartworm test we use here at Falls Village also detects 3 common tick-borne diseases – Lyme, Ehrlichia and Anaplasmosis. These can also affect your pet’s health, so it is important to check for them on a regular basis.

MYTH | I brought in a stool sample from my dog and it was negative, so he does not have heartworms.

Checking a stool sample for intestinal parasites is an important part of your pet’s routine wellness check. However, to test for heartworms a blood sample is needed. It takes as little as three drops of blood to run the test.

MYTH | I use those flea drops every month, I don’t need to use another product for heartworms.

There is a wide variety of products available to protect your pet from fleas, ticks, intestinal parasites and heartworms. However, there is currently not any one product available that covers all of these parasites. Many of the available heartworm prevention products do also provide control of intestinal parasites.


Talk to your Raleigh, NC veterinarian to determine which products are best suited for your pets!