Heartworm Disease

Heartworm Disease

Heartworm Disease is a very serious problem in the Kansas City area, affecting many dogs and cats. Heartworm Disease is caused by a parasite known as the Heartworm (Dirofilaria immitis), which is transmitted by mosquitoes.

Paw Points

  • Heart Worm Disease is common in Missouri.
  • Carried by Mosquitos
  • Affects Indoor & Outdoor Pets
  • Dogs are most at risk.
  • Blood Tests Yearly
  • Give Heart Worm Prevention Monthly, Even in Winter Months
  • Heart Worm Preventative is more affordable than Heart Worm Treatment.

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 1 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 doesn't mean your pet is not infected.

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.

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® or Sentinel®. 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, but it and Revolution® are also effective in preventing heartworm disease (and fleas!) in cats. Both are a topical product that goes on the back of the pet's neck much like flea products. 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.

Preventing heartworm disease is just as important as getting your pet vaccinated. Dogs have always been the main focus of preventing heartworms, but newer information shows a need to protect cats as well. Advantage-Multi® and Revolution® are the only products approved for use in cats.

Above is a table to help you decide the best heartworm prevention for you--all of which are available at Gladstone Animal Clinic. Also below is a list of clinical signs seen in moderate to advanced heartworm disease. Remember, early disease often does not have any symptoms; getting your pet tested is the best way to know for sure. Call us if you have any further questions about heartworm testing or prevention. Have your pet tested for heartworms today!

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