Heartworm Disease

Heartworm Disease is of very serious concern for dogs and cats in the Kansas City area. Heartworm Disease is transmitted by mosquitoes and is caused by a parasite known as the Heartworm (Dirofilaria immitis).

Adult heartworms are large, white worms that grow up to 12 inches long. They live primarily in the large vessels that carry blood from the heart to the lungs (also known as pulmonary arteries). When both male and female worms are present in these vessels, young heartworms known as microfilarie are produced and are released into the circulatory system of the animal. If a mosquito then bites an infected pet, it sucks up the microfilariae, along with the blood it ingests. During the next 2 weeks, the immature heartworm develops inside the mosquito. After that time, when the mosquito bites another animal to feed, it injects the heartworm into the animal’s blood stream. The heartworm continues to grow inside its new host and will eventually make its way to that animal’s heart in the next 3 to 4 months. Once there, the adults will produce microfilarie and the cycle of disease begins again. The life span of a heartworm is thought to be between 5 to 7 years.

Anywhere from one to over 200 heartworms may reside in the heart and pulmonary arteries. The arteries become thickened and inflamed due to the presence of the worms. This causes the blood pressure in that area to increase and forces the heart to work harder. Over time, this increased cardiac output can result in congestive failure of the heart and other organs, ultimately leading to death. Since it takes heartworms so long to develop, it can be months before any clinical signs of disease are present in your animal. Just because you do not see any symptoms does not mean that your pet is free of infection.

Prevention of Heartworms

Heartworms can be prevented in a number of ways, and for many decades the most common type of preventative for dogs are once a month oral medications such as Interceptor®. Both are very effective against heartworms. In recent years, combination products that prevent heartworms and kill fleas have emerged. Advantage-Multi® is not only a great product for dogs. For the most effective prevention of heartworms, all heartworms preventatives need to be given once a month, 12 months a year (remember, warm snaps can come suddenly during the winter in the Midwest–long enough for mosquitos to emerge).

All dogs must be tested for heartworms before starting a monthly preventative. If your pet has heartworms when you give the medication, you could run the risk of causing a severe allergic reaction. With this in mind we recommend all dogs over the age of 7 months be tested prior to starting the preventative, and then each year before starting on it again if the preventative is stopped during the winter months. Even if the preventative is given monthly all year long, with no breaks in the dosage schedule, a heartworm test is still recommended every year to ensure your pet is protected.

Testing for Heartworms

In dogs, a simple blood test can easily pick up even early heartworm infections. Though heartworm disease can be lethal, it is potentially treatable if caught early enough. Hospitalization will be needed for your pet and a series of injections over a few days are required to slowly kill the heartworms. After treatment, your pet will need to be kept very quiet with minimal activity for many months until the worms are completely broken down by the body, and no longer at risk of causing a thromboembolic event (heart attack). However, the best way to avoid heartworm disease is prevention.