How to Know if My Dog Has Heartworms

Signs that Your Dog has Heartworms

“How do I know if my dog has heartworms?” As a former veterinarian’s assistant, I used to hear that question all the time. Luckily, the answer is a simple one.

Knowing if your dog has heartworms is easier than you might think. Only a blood test can positively determine if heartworms are present inside your dog.

Of course, you can’t give your dog a blood test every week. That’s why heartworm prevention is so important. Heartworms can be lethal if not treated soon enough, and the best course of action is to make sure your dog doesn’t get them in the first place.

The following article will discuss what heartworms are, where they come from, and how to get rid of them. You’ll also learn a few early warning signs of heartworms to look out for.

What Are Heartworms?

Heartworms are parasitic organisms which are spread by mosquitoes. They appear to be thread-like worms, and they can infect dogs, ferrets, cats, coyotes, foxes, wolves, and even humans.

The name “heartworm” comes from the fact that the adult worms usually live in the right atrium of the host’s heart. They can reside there for many years before the host dies.

Where Are Heartworms Found?

Heartworms can be found anywhere mosquitoes are present. They are located in every American state (except Alaska), parts of Canada, Japan, Australia, the Middle East, southern Europe, Southeast Asia and South America. The greatest concentration of heartworms are found along the Mississippi River and the Atlantic Coast (from Texas to New Jersey).

Stages Of A Heartworm

The life of a heartworm can be broken down into several stages:

  1. Heartworms are introduced into an animal via a mosquito bite. This is known as the prepatent period, and it usually takes 6 to 7 months for the worms to mature and begin living in the heart of the host.
  2. Once inside the right atrium, the heartworm gives birth to thousands of young every day. These undeveloped microfilaria then circulate in the bloodstream and wait to be sucked out by a mosquito.
  3. When the microfilaria are ingested by a mosquito, they grow into larvae and travel to the salivary glands. Then, when the mosquito bites an animal, the larva are introduced and slowly make their way to the host’s heart in order to begin reproduction.

Symptoms of Heartworms

In many cases, a dog with heartworms will show no signs of infection. Sometimes, a migrating heartworm can end up in the eyes, brain or artery of the leg. This can result in seizures, blindness or the inability to walk.

Dogs that are active or heavily infected may cough or become exhausted during exercise. In more advanced stages, a dog with heartworms may suffer from extreme weight loss, coughing up blood and fainting spells. This will culminate in the dog’s death, usually from congestive heart failure.

Treatment of Heartworms

The most common treatment for heartworms is a drug known as Immiticide. Heartworms can also be surgically removed, but this is only recommended in very advanced cases.

Prevention of Heartworms

Heartworm prevention is the most effective way to safeguard your dog’s health. Leading drugs are ProHeart, Heartgard, Interceptor and Sentinel. When administered properly, heartworm medication will prevent infection more than 99 percent of the time.

Available in chewable tablets, these anti-heartworm pills are administered on a monthly basis. A veterinarian can also give your dog an injection which will effectively prevent heartworms for either six or twelve months.


  1. joan brady says:

    My black lab who is 6 years old gets diareha a lot. It usually last 2-3 days. Right now she has it and seems quite lathargic, what can I do?

  2. Joan, your best bet is to take her to your vet. There, they can do some simple blood tests that can rule out (or confirm) lots of potential causes of the diarrhea. Once you’ve ruled those things out, you may find that it’s as simple as the type of dog food that you’re feeding her. Good luck!

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