Heartworms are worms that live the final stages of their lives inside the hearts of host animals. Their hosts are usually dogs, though cats and ferrets can also get heartworms. If left untreated, heartworm infestation is fatal, but the good news is that a simple monthly treatment starting at 6-8 weeks of age can protect your dog from getting heartworms and ultimately, save your best friend’s life.
How do dogs get heartworms?
The heartworm lifecycle (from birth to death) is rather complicated. They hatch from eggs of a mature female heartworm, and in their first stage are tiny creatures called microfilaria. Microfilariae are so small they can circulate in the bloodstream of an animal.
While floating in the bloodstream they are sometimes sucked out of the host’s body by a new host: a mosquito. Once inside a mosquito, the microfilariae are able to mature into larvae. These larvae are then able to migrate to the salivary glands of a mosquito, and when the mosquito bites an animal they enter that animal through the bite wound.
Once inside an appropriate host, the larvae grow, molt (shed their skins), and become larger and larger worms. Ultimately, flowing through the host’s bloodstream, they find their way to the host’s lungs, and eventually the heart, and live there as mature worms until they die or the host dies. Heartworms can live in a host for many years. Mature female heartworms can grow to be as large as 14 inches long.
What happens to a dog infected with heartworms?
As previously stated, heartworm infestation is fatal in dogs. Dogs die from heartworms because the worms inhabit the heart and pulmonary tissues as they grow. Over time they cause irreversible damage to those areas and begin to block the flow of blood to other parts of the body as well. Heartworms in dogs can also affect the function of various arteries, and in turn, lung function. In addition, in an effort to combat heartworms, the body often goes into a state of heightened and ineffective immune response. This does not kill the heartworms but may cause the body to attack itself causing inflammation and damage to other systems in the host’s body.
The body, with a poorly functioning heart and arterial system, will begin to fail. Eventually, the heart will fail entirely killing the dog; though they may die earlier from a variety of complications.
Heartworm infection can be treated and is more likely to be successful based on several factors, including the overall health of the dog and the dog’s age. There are 3 ways to treat heartworm: 1) Injections of Immiticide® (generic melarsomine, an arsenic-based heartworm-killer); 2) Monthly preventative heartworm medications and 3.) Open-heart surgery
The American Heartworm Society prefers that whenever possible dogs are treated with melarsomine injections because heartworms cause damage as long as they are present in the heart, it’s ideal to eliminate them as soon as possible.
Heartworm Prevention in Dogs
Dogs should receive monthly, preventative treatment, year-round if they live in North America. Before receiving treatment, dogs over seven months of age must be tested to be certain they do not already have heartworms. It’s dangerous to give heartworm prevention medication to a dog that is already infected with heartworms.
There are many heartworm treatments available. The treatment that’s best for your dog should be determined in consultation with your veterinarian. Heartworm prevention medication sometimes comes as part of a combination medication that also prevents or treats other parasites such as fleas, ticks, or mites.
Loving your dog = Preventing heartworms
If your dog is not yet on heartworm prevention medication, please see your vet as soon as possible to get them started with treatment. For more information about heartworm prevention and treatment visit the American Heartworm Society.