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Common Heartworm Symptoms in Dogs

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What Are Heartworms?

Heartworms are worms that live in the heart, lungs, and blood vessels of infected dogs. Since dogs are their natural host, they live in their organs and mature into adulthood, growing up to one foot long. Heartworms tend to prefer warm, moist climates, so they are most common along the southeast Atlantic coast.

What causes heartworm in dogs? Mosquito bites.

When a mosquito bites an infected dog, they ingest baby heartworms via the dog’s blood. These baby worms grow into infective larvae, which can migrate to the mosquito’s proboscis. Now, that same mosquito can bite and infect other dogs with the infective larva. Inside the host (the dog), the larva matures into full-grown heartworms in a matter of months.

What Are Common Signs of Heartworm in Dogs?

A definitive diagnosis of heartworm in dogs requires a trip to your vet. They will use physical examination, blood tests, urinalysis, and scans to determine if your dog has heartworm. Heartworm disease falls into four classes:

Class One: Mild, Asymptomatic Heartworm.

Class Two: Moderate Heartworm.

Class Three: Severe Heartworm.

Class Four: Caval Syndrome.

Depending on the stage of the disease, symptoms will vary. Below are some of the common heartworm symptoms in dogs for each of its four classes.

Class One:

  • No clinical signs or laboratory abnormalities
  • May result in lower energy and occasional cough

Class Two:

  • Difficulty exerting energy
  • Increased lung sounds
  • Potential anemia and proteinuria

Class Three:

  • Anemia and weight loss
  • Rapid breathing even when resting
  • Difficulty exercising
  • Coughing up blood
  • Severe cough
  • Abdominal swelling
  • Notable abnormalities in lab results

Class Four:

  • Sudden collapse
  • Blood in urine
  • Difficulty breathing
dog sitting on ground

Is Heartworm Treatable in Dogs?

When caught early, heartworm is treatable in dogs, however, the treatment is a rather arduous and complicated journey. It takes about a year to complete a full heartworm treatment.

Your vet will administer a series of injections of melarsomine, which is used to kill adult heartworms. The frequency of these injections will depend on the severity of your dog’s case. Generally, this means an initial injection, one month of rest, then two more injections administered 24 hours apart.

Your dog will also receive a treatment to kill any heartworm larva to prevent future infection. Additionally, your dog will start on a heartworm preventative following treatment. Read more from VCA Hospitals for further details about treating heartworm in dogs.

Frequently Asked Questions

Can a Dog Live with Heartworms?

No, a dog cannot live with heartworms. If left untreated, the disease is fatal. Heartworms live for 5-7 years in dogs and continue to reproduce during that time. The damage to the dog’s heart, lungs, and blood vessels worsens as the heartworms multiply.

Can Humans Get Heartworms?

Yes, people can get heartworms. However, we are not natural hosts for them, so they very quickly die off before maturing into adulthood.

Are Heartworms Contagious?

Yes, heartworms are contagious between mammals, including cats and dogs, via mosquito bites. When a mosquito bites an infected dog, it can then transmit the disease to the next animal it bites.

If you suspect your dog might have heartworms, take them to the vet right away. The earlier they are caught, the better the chance your vet has to treat and cure your dog.

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