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What is the treatment for heartworm in dogs?

Larry Sackett


Dr. Kara S. Duffy, a veterinarian at the Atlantic Animal Hospital, said that heartworm in dogs (and cats) can easily be prevented, but “it’s very challenging and expensive to treat.”

According to Duffy, the infection is caused by bites from mosquitoes that carry the heartworm larvae, called microfilaria. The larvae are passed to the dog and go through an incubation period of about seven months while migrating through the blood stream to the heart.

Male heartworms are a few inches long and look like angel hair spaghetti. Females can reach up to 12 inches; these are the worms that do the most damage. Heartworms lodge in the heart, lungs, and surrounding blood vessels. It’s not uncommon to find dozens of worms in a dog.

Dogs can go for years after being infected before showing any symptoms, such as a dry cough, heavy breathing, and difficulty exercising, as the worms damage the pulmonary arteries. Left untreated, heartworms can kill the pet.

“We can usually diagnose heartworms with a simple blood test that takes just a few minutes,” Duffy said. “The test is very accurate.” Once a dog has been diagnosed with heartworms, a vet will determine if the pet is healthy enough for treatment, which includes X-rays to see if the heart is damaged and blood tests for liver and kidney functions.

“We give an infected dog a series of three injections of an arsenic-based drug, Immiticide, over a 31-day period,” Duffy said. “We also treat the animal with anti-inflammatory drugs and antibiotics.”

Immiticide kills the worms. Another anti-heartworm drug is used to kill any larvae in the bloodstream and prevent re-infection. Once the worms die, they break into pieces, which occasionally can cause a blockage of the pulmonary vessels, potentially resulting in death.

Duffy said it’s very important to keep a pet quiet and to avoid exercise for a period of six to eight weeks after treatment to help prevent any further pulmonary damage as the worms break up.

“Prevention is way easier and much less expensive than having a dog become infected,” Duffy stressed. She said the treatment can cost hundreds of dollars.

There is no way for a dog to avoid being bitten by mosquitoes, so a pet owner needs to periodically give the animal an oral preventive or an injection. Dogs can be given an oral preventive that costs as little as five to seven dollars a month. An alternative is an anti-heartworm drug that can be injected once every six months if the dog won’t take a pill. Some heartworm preventives also protect against fleas and intestinal parasites.

Atlantic Animal Hospital tests every new dog they see for heartworm disease, according to Duffy. Dogs they see on a regular basis and which are taking preventative medicines are tested every one to two years.


Are there county ordinances concerning out of control numbers of stray cats?

What pesticide does New Hanover County spray for mosquitoes? Is it harmful to humans or pets?



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laurie davis

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