Charlottesville Animal Health Care - Old Dominion Animal Hospital

What Every Good Pet Owner Should Know About Heartworm Prevention

Mosquito on Dog

Heartworm disease is a potentially life-threatening condition caused by parasitic worms that can live in the heart and lungs of dogs, cats and other mammals. The good news is that you, the owner, can easily prevent it by giving your pet medication. However, owners must be vigilant to help ensure that their pets are properly protected from this dangerous disease.

Only mosquitoes spread heartworms, so areas with a large mosquito population will have a greater incidence of heartworm disease. As the name suggests, heartworms live in the heart and pulmonary vessels of an infected animal. The adult heartworms produce offspring called microfilariae. When a mosquito bites an infected pet, it sucks out blood containing the microfilariae. After some maturation inside the mosquito, these offspring develop into infective larvae. This step is necessary for heartworm to spread. When the mosquito bites another pet, the infective larvae are passed on, and the process starts again as the larvae mature into adult heartworms. These heartworms can cause severe damage to the >hearts and lungs of an infected pet.

Protecting Your Pet

The consequences of heartworms can be life threatening, which is why it is so important to properly protect your pet from this disease. Fortunately, preventing heartworm disease can be as easy as giving your pet a monthly preventive — the key is making sure you do it consistently.

Part of the problem for pet owners is that, in many regions of the United States, heartworms are seasonal. Depending on where you live, mosquito season can last only three or four months of the year, or as long as year-round. So it can be challenging not only to remember that you actually need to start heartworm preventives but also to know when to start them. Many veterinarians now recommend most pet owners give year-round heartworm preventives. This takes the guesswork out of remembering to start the medication and when. However, it is a good idea to ask your veterinarian about the schedule of prevention she recommends.

Start With a Test

Before you begin administering a heartworm preventive, it is extremely important to have a test done to make sure your pet does not already have heartworms. If the test comes back positive, your veterinarian will discuss next steps and treatment options.

The most common test used for detecting heartworms in dogs is an antigen blood test. This test detects specific antigens (substances that create an immune response within the body) from adult female heartworms. It takes about seven months from the time a dog is bitten by an infected mosquito until an antigen test can accurately detect the presence of adult female worms. Even pets who spend most of their lives indoors need protection from heartworms.

Unfortunately, although antigen testing may be sufficient for dogs, detecting heartworms in cats can be a bit more complicated. Additional tests, such as an antibody test, an echocardiogram (a noninvasive sound reading for visualizing areas within the body) or X-rays, may be used to determine if the cat has heartworms.

Prevention Is the Best Medicine

Faithfully administering a heartworm preventive is essential for keeping your pet protected against heartworms. Many preventives will also protect your pet from other parasites like roundworms, hookworms and even fleas. Most preventives are given on a monthly basis, so it is important to establish a regular routine for giving them to your pet. It is also a good idea to keep a record of each time you administer the preventive — this takes the guesswork out of remembering if and when it was given. A great way to help remember when to give your pet his preventive is to ask your veterinarian whether she offers a reminder service for regularly administered medications.

Just Do It

The key to protecting your pet from heartworm disease is awareness. Although heartworm disease is treatable, the procedure can be costly, and your pet may need to be hospitalized.

Heartworms are easy to prevent — you just need to remember to test per your veterinarian’s recommendations and give preventives regularly. Your veterinarian can help you decide the best course of prevention for where you live. Make heartworm prevention a regular part of caring for your pet — it is easy to do, and your furry companion will be glad you did.


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