Heartworm disease is a very serious and preventable condition in dogs and cats. As you can see from the incidence map below, animals all across the United States and throughout Florida are at risk of contracting this deadly disease. Preventing heartworm disease is as easy as administering a monthly heartworm preventive to your pets.
How Do Animals Get Heartworm Disease?
Mosquitoes spread heartworms (Dirofilaria immitis) when they bite an animal. The heartworms carried by the mosquitoes are in a larval phase, and these larvae mature into adult heartworms over a period of months after entering the animal’s body. The adult heartworms then reproduce by producing microfilaria in the animal’s bloodstream, which infect mosquitoes. Once the microfilaria are in the mosquito, they mature into larvae where they wait to be passed on to another animal.
Why Are Heartworms So Dangerous For Pets?
Adult heartworms live in the arteries in the lungs and sometimes on the right side of the heart. The worms can block the flow of blood or cause emboli in the lungs. Either of these conditions can be fatal to pets. Kidney damage can also occur from the immune system trying to fight off the heartworm infection and can progress to kidney failure.
What Are The Signs Of Heartworm Disease?
Animals that have early infections often show no signs of disease. In later stages in dogs, a variety of signs can be noted including weight loss, cough, lethargy, fatigue, decreased appetite, and difficulty breathing. In the later stages in cats, a variety of non-specific signs can be noted including vomiting, gagging, difficulty breathing, cough, weight loss, and lethargy. Successful treatment of heartworm in dogs is much more likely if heartworms are detected before symptoms occur. This is why annual heartworm testing is so important!
How Is Heartworm Disease Detected?
In dogs, a simple blood test to detect adult female heartworm antigens is performed to diagnose heartworm disease. We perform this test in-house and it takes about 10 minutes. Because it takes the heartworm larvae 6 months to develop into adults, a dog in the first 6 months of heartworm infection may test falsely negative for heartworm disease. We recommend testing all dogs yearly for heartworms.
In cats, the diagnosis of heartworm disease is more complicated. As compared to dogs who typically have many heartworms, cats usually only have one or two heartworms. The antigen test used for dogs only detects female worms and may be falsely negative in infected cats. When the suspicion of heartworm disease arises, a heartworm antibody test is usually recommended. The antibody test detects the immune system’s response to heartworms. This test is not foolproof, so the diagnosis of feline heartworm disease is usually made by combining the results of other diagnostics (ie. radiographs, bloodwork, physical exam, ultrasound) with the results of the antibody test.
How Do I Prevent Heartworm Disease?
Preventing heartworm disease has never been easier! There are a multitude of safe and proven medications for your pets. All of these need to be given monthly to be effective. Our recommended heartworm preventatives are Trifexis and Heartgard for dogs and Revolution for cats.
How Is Existing Heartworm Disease Treated?
Most cases of heartworm disease in dogs are treated with a medication called Immiticide that is injected into the muscle. This medication kills the adult heartworms in the animal’s body. Very severe heartworm infections may require surgical therapy, but this is very rare. Treatment for heartworm disease can be costly and is not without risks. Therefore, prevention is key.
Unfortunately, cats do not tolerate the Immiticide treatment used in dogs. Treatment in cats is focused on controlling clinical signs. Again, prevention is key, since there is no treatment to kill adult heartworms.