Heartworm Disease

Heartworm Disease in Dogs

Heartworm disease is a life-threatening parasitic infection by Dirofilaria immitis. This disease is preventable. Worms living in the vessels reduce the heart’s ability to move blood. This leads to heart, lung, and kidney disease.

How does my pet get heartworm disease?

Mosquitos transmit the juvenile heartworm (microfilariae) through a blood meal. Microfilariae mature to adults in 6 months. The worms can grow to over a foot long and live in the vessels of the lungs and heart. The worms can begin to reproduce within 5-7 months and allow the spread of the parasite to other animals via mosquitos.

Is my pet at risk?

Heartworms are a potential threat in every state that has mosquitos. All dogs and cats are susceptible to heartworm infection. This includes indoor pets and those that only go outside occasionally. Animals that have been on heartworm preventative still need to be tested yearly as the preventative only affects certain life stages of the worm. One missed or late dose could make your pet susceptible to contracting heartworm disease.

How will I know if my pet comes down with heartworm disease?

If your pet has been recently infected or there are a low number of worms, there may not be any clinical symptoms yet. A heartworm infection can be detected by a blood test after the worms are 6 months old. The diagnosis of heartworm infection in cats can be more difficult than it is with dogs and a series of different tests may be needed.

Once the adult worms develop in the lungs and create increased stress on the heart, signs of heartworm disease can be seen. Symptoms can include coughing, lethargy, loss of appetite, difficulty breathing, exercise intolerance, and rarely sudden death in cats.

What is the treatment for heartworm disease?

Immiticide is the only FDA-approved treatment available for dogs. There is substantial risk involved in treating dogs for heartworms. Serious complications are much less likely in dogs that have not developed symptoms and are otherwise in good health. The arsenic in Immiticide targets the adult worms present in your dog. As the worms die, emboli can form which may lodge in the lungs and cause inflammation. The dog will require complete rest throughout the treatment period and medications may also be needed to reduce inflammation.

There is currently no effective and safe medical treatment for heartworm infection in cats. Medications can be given to reduce the inflammatory response.

How can I prevent heartworm disease?

Heartworm infection is almost 100% preventable in dogs and cats. Prescription medications kill immature heartworms from the previous month. They do not prevent exposure. We recommend year round prevention to ensure full coverage for the entire heartworm season which leads to less missed doses. Year round heartworm medications also control intestinal parasites and keep drug levels more consistent to combat resistance.

If you’d like more information, visit the American Heartworm Society website at www.heartwormsociety.org.


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