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Heartworm in Dogs: What You Need to Know

Learn what you need to know about canine heartworm.

Heartworm in dogs is widespread and commonly diagnosed in the United States. It's spread by the bites of infected mosquitos—a mosquito bites a dog that has it and then bites another to spread it.

Heartworm can and often is fatal in dogs that aren't treated. Here are some essential things to know about it.

Heartworm Disease Is Serious

Spaghetti-shaped, long worms live in the blood vessels of your dog's lungs and heart during this condition. They eventually do permanent damage to those organs and the blood vessels. When the worms die, they break into pieces and try to flow out of the vessels, get lodged, and cause respiratory problems.

Even Dogs That Don't Go Out Much Need Preventative

Heartworm preventative comes in many forms, and which one is right for your dog is best decided by you and your veterinarian. But even dogs that don't go outside much need protection. That's because only one bite is required to transmit the condition, and your dog will be outside sometimes. Plus, mosquitos can hitch rides inside.

Heartworm Treatment Is Risky

The treatment for heartworm disease in dogs is a series of injections in the big muscles of the dog's back. As the worms die, significant complications can occur, such as respiratory distress, and toxin release from the dying worms can become poisonous to the dog. Dogs must be kept quiet for weeks after treatment as the adult worms die to keep the dog from overstressing the lungs, and other medications might be needed to kill non-adult worms. The procedure is costly and can, itself, be deadly.

Signs of Heartworm Disease May Be Vague

A dog that has heartworm disease might not show any discernable signs of it for a long time. When they do show signs, they can be vague and overlooked. Coughing, exercise intolerance, and occasional labored breathing might occur in some dogs.

Heartworm Disease Can Be Prevented

Heartworm disease is preventable, and your dog should take medication year-round for protection. That's because it's hard to know when mosquitos will come out because fluke warm snaps can happen. Also, it helps you establish a routine of giving it and ensures you won't forget and start too late after warm weather and mosquitos arrive.

Dogs should also have a heartworm test every year, even if they are on year-round preventative. That's because dogs may vomit or spit up a pill without your knowledge.

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