Heartworm Disease

By Dr. Melissa Hawkins

            As someone that has been working in the pet healthcare industry for 14 years, I am amazed at the number of pet owners that don’t know about heartworm disease.  Not to worry!  I’m here to educate you, and help to keep your pet happy and healthy!

Heartworms are common throughout the world, and heartworm disease has been documented in every state of the US, including Alaska!  Heartworms are spread through mosquito bites, so it stands to reason that any area with mosquitoes has the potential to have heartworms as well.  Most places we and our pets live are warm enough to have a healthy mosquito population for at least some period during the year.  This is especially true for the Midwest, including Indiana.  We have plenty of water here, and even this past winter in Indianapolis didn’t get cold enough to kill off the mosquito population completely.

            When a mosquito carrying heartworm larvae bites your dog or cat, one (or more) of the microscopic larvae is deposited under the skin.  This larva makes its way to the vessels associated with the heart and lungs, where it grows into a long, white worm.  These worms sometimes reach 1 foot in length!  With the presence of adult heartworms, the heart has to work harder to pump the same amount of blood throughout the body.  This in turn causes the heart muscle to enlarge.  Congestive heart failure often develops.  Abnormal heart rhythms and sudden death are unfortunately common.  Sometimes there are no outward symptoms of infection at all, except for sudden death.  Severe inflammation also develops in the lungs, making it harder for the pet to breathe.  Cats develop symptoms similar to asthma.  Treatment of heartworm disease in dogs is possible, but it is very expensive, and fraught with risks.  Some patients do not survive the treatment process for this disease.  There is no cure for cats.

            But there is hope!  This disease is completely preventable!  Administering a monthly heartworm preventative to your pet all year round is the best way to prevent heartworm disease.  And not only does your pet receive heartworm protection with a monthly product, but they also receive protection against the most common intestinal parasites – hookworms, roundworms, and usually whipworms as well.  Many products also include flea protection.  There is protection against ear mites available as well, which is great for outdoor cats.

            Now some of you might be thinking, “But Dr. Hawkins, we live in Indiana.  It gets cold in the winter.  We really don’t have to give the heartworm preventative all year round.” 

Yes, it gets cold in the winter.  But remember this past winter in Indy?  It really didn’t get cold enough to kill off the mosquito population completely.  No one could have predicted that early enough to let you know the importance of year round heartworm prevention for your pet.  Not to mention that some intestinal parasite eggs and larvae can still live in the environment, despite freezing temperatures.  These parasites can infect your pet in the winter, and some of them can even be spread to their human caretakers!  

 (Click here for the latest U.S. Heartworm Incidence Map by the American Heartworm Society! )

            I also frequently hear from clients, “Dr. Hawkins, he/she rarely (or never) goes outside, so there is no risk of a mosquito bite.”  This is not true!  I have found plenty of mosquitoes in my house, and I’m betting you have, too.  Mosquitoes can, and do, get into the house, leaving even your “indoor only” cat at risk of infection. 

            Noah’s Animal Hospitals recommend yearly heartworm blood testing for all dogs each year.  This is usually done at the same time as the annual physical examination and vaccines. 

Now I bet some of you are thinking, “But Dr. Hawkins, you just told us to give our pet’s heartworm preventative all year round.  This means there is no reason to test them every year.  If they receive preventative every month, there is no chance they will get heartworms.” 

This would be true in a perfect world.  However, we lead busy lives.  We don’t always remember to give our pets their heartworm preventative pill on time every month.  Administering the dose even 1 or 2 days late leaves a risk that your pet could develop a mature heartworm infection.  And I’ll be honest with myself – sometimes my pets don’t receive their preventative tablet on time.  I forget.  And if I am forgetting this small task every month, I know some of you are forgetting as well. 

Undetected heartworm infection is extremely detrimental to your pet.  Yearly testing ensures that we will catch an infection in your dog early if one develops.  Heartworm treatment is expensive and dangerous, but treating early in the course of the disease is much safer and more successful for your pet. 

Check out this video by NFL football player, LaDainian Tomlinson regarding his family's experience with heartworm disease.

Unfortunately there is no accurate yearly blood test for cats for this disease at this time.  We’re waiting for it.  The best thing you can do to protect your cat is monthly administration of a heartworm preventative product.  Please schedule an examination for your cat if you notice something out of the ordinary.

This year to date in Marion County, over 500 heartworm positive dogs have been diagnosed.  That is over 80 cases a month, in 1 county.  We hope to help stop these rising numbers by ensuring our patients receive monthly heartworm preventative, all year round.  As always, we strive to be your partner in your pet’s healthcare!