heartworm 2
We talk a lot about Heartworm infection. We urge to you keep your pet on preventives and to test for evidence of heartworm infection year after year after year. The problem is, what we really need to talk about is Heartworm Disease. It is the shadow in the room that both frightens and motivates us.

Most people understand the basics of Heartworm in dogs. An infected mosquito bites your pet and leaves a larval worm on the skin where it enters the host (your dog) through the bite. Over a period of time the larvae migrate to the heart where they will become adults. The entire process takes about 6 months. Adult Heartworms are big, around a foot in length. This is Heartworm infection. There may be no signs at all.

Heartworm Disease is another story. Dogs who have Heartworm Disease are very sick indeed. They have an illness that is both highly complex and life threatening. There are four recognized stages of Heartworm Disease.

Stage One: Mild with little to no clinical signsheartwormLifeCycle

Stage Two: Dog develops a cough

Stage Three: Cough present with abnormal lung sounds and exercise intolerance

Stage Four: Cough, abnormal lung and heart sounds, exercise intolerance and difficulty breathing, fainting, enlarged liver, fluid in the abdomen and lungs, death

Caval Syndrome: This is the nightmare scenario of Heartworm Disease. In Caval Syndrome there are so many worms present in the heart that they actually back up into the vena cava and wreak havoc in the entire body. Shock, liver failure, and a lack of the ability to clot the blood may occur and result in rapid death. Sometimes surgical removal of the worms is used as a last ditch effort to treat Caval syndrome.

So what exactly is happening in your pet’s body to cause all these signs?heartworm map

Arteries are not made for housing worms. Think about living, eating, breeding, pooping, foot long worms living in your arteries and heart. Not good. Which is why very shortly after they arrive, the body releases an army of immune cells ready for combat. Sadly, the worm’s large size make them impossible for the body to destroy. The end result is chronic inflammation which causes dilation and twisting of the arteries. This in turn impedes the proper flow of blood causing abnormal clotting and aneurysms. The end result is scarring and hardening of the sensitive tissues of the lungs making them no longer able to provide oxygenation to the rest of the body. Ouch.

It should come as no surprise then, that we see coughing and exercise intolerance. The constant presence of inflammatory cells may also precipitate pneumonia, damage to the kidney, liver, eyes and joints.

And it gets worse. In time, as worms and accompanying inflammation and clotting make it more and more difficult for the heart to pump blood effectively, it starts pumping harder. Overworking the heart can only go on for so long before Heart Failure occurs. Heart failure is defined as an enlargement of the heart and thickening of its walls. Think of it as a pump that has been working non-stop in a very bad flood. Eventually it just gets worn out. An animal in Heart Failure may develop a pot belly from fluids that accumulate in the abdomen and severe problems with breathing due to fluid and scarring in the lungs. They will be lethargic and very unthrifty. Eventually after a long and tortuous illness, they will die. They may be quite young. It is very sad and very preventable.heartworm disease

So…hopefully this will explain our obsession with getting and keeping your dog on Heartworm prevention.