Pit Bull 101: Heartworms in Dogs

What is Heartworm Disease?

Heartworm disease is a serious and potentially fatal condition caused by parasitic worms living in the arteries of the lungs and occasionally in the right side of the heart of dogs, cats and other species of mammals, including wolves, foxes, ferrets, sea lions and (in rare instances) humans. Dogs and cats of any age or breed are susceptible to infection.

Dogs or other animals harboring adult worms are the recognized reservoir of heartworm infection. The disease is spread by mosquitoes that become infected while taking a blood meal from an infected dog. When the mosquito then bites another dog, cat, or susceptible animal, larvae are deposited on the skin and actively migrate into the new host. For about 2 months the larvae migrate through the connective tissue, under the skin, then pass into the animal’s venous blood stream and are quickly transported to the arteries of the lung. It takes a total of approximately six months for the infective larvae to mature into adult worms that begin producing offspring. Adult heartworms can live for five to seven years in the dog.

How is Heartworm Disease Prevented?

A heartworm prevention program is effective and simple, and consists of three parts:

  1. Regular Blood Testing – This ensures your pet is free from heartworms before he begins or continues on his preventive medication. Your veterinarian will advise you as to the frequency of regular blood tests.
  2. Preventive medication – This means administering a heartworm preventive to your pet for at least six months to a full year depending on the mosquito season. Prevention for dogs includes monthly oral preparations.
  3. Reducing your pet’s exposure to mosquitoes – This means making your pet’s environment less hospitable to mosquitoes. This decreases the risk of your pet being infected with heartworm in the first place.

Heartworm prevention is safe, easy and inexpensive compared to treating a dog or cat after worms have matured into adults. While treatment for heartworm disease is possible, it is a complicated and expensive process, taking weeks for infected animals to recover and there is usually permanent damage to the heart. By investing in a preventive medication, you will spare your pet from this deadly disease and its complicated treatment. Talk to your veterinarian today to start a prevention program for your pets.

How is Heartworm Disease Treated?

Although heartworms can be fatal and treatment for the disease involves risk, the condition is usually curable. Treatment requires careful medical care and complete rest at home afterwards.

The first thing your vet will do is evaluate your dog’s health, performing a physical examination, laboratory tests and chest x-rays to evaluate the condition of the heart and lungs. They might find other problems that need attention first, or if the heartworm infestation is very severe, they might want to adjust our treatment plan.

Adult heartworms are about six inches long and live mostly inside the heart. Baby heartworms are microscopic and live within blood vessels throughout the body. Each stage must be treated separately. First, your vet will eliminate the adult worms by giving a series of injections spaced out over a two day period.

When treatment is finished your dog’s heartworms will be dead or dying. That’s good, but the heart is still full of worms. The worms gradually break into smaller and smaller pieces until the fragments are tiny enough for the body to eliminate them. The critical period is when worm fragments are small enough to disperse into the body but still large enough to plug small arteries in the lungs. Vigorous activity makes the heart pump faster, pushing bits of dead heartworm out into small blood vessels where they can cause trouble, so vigorous activity must be avoided.

After treatment, your dog will need significant rest and follow-up visits to the vet to ensure all of the worms have been eliminated. Please consult your veterinarian for detailed treatment arrangements.