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Heartworm Treatments

Heartworm Treatments


What is the Best Heartworm Treatment?

A heartworm is a parasite, which a mosquito transmits from one canine to another. When a mosquito sucks up blood from a canine, microfilaria in the blood enters the insect. Microfilaria undergoes three larval development stages within about two weeks.

At the third stage, it reaches the salivary glands of the mosquito.  It is at this stage that the mosquito can transmit the heartworm parasite to the next victim.  The mosquito extends its proboscis and bites the animal, transmitting the microfilaria through saliva. Within about 70 days, the parasite undergoes two last larval stages and reaches the heart through the bloodstream, where the worm will grow rapidly until its death more than five years later.

The heartworm parasite’s growth can clog the bloodstream, similar to atherosclerosis in humans.  It can even block pulmonary arteries. In addition, the worms cause damage to those arteries. Blood vessels become inflamed and fluid accumulates. Eventually, blood pressure increases until heart failure.

Heartworm Treatment for dogs

If a dog waits for the first treatment after a heart failure, then there might be too much damage to the dog’s organs. Surgical removal of the heartworms may be the only option to increase the chances of survival and health of the dog.

The specific heartworm treatment is on a case-by-case basis depending on the severity of the disease. Veterinarians treat Microfilaria larvae and adult worms differently. Killing adults may bring about complications, including blockage and inflammation due to worms’ decomposition.

The veterinarian assesses the dog and decides whether surgical removal is necessary as an initial step. Adulticide medication, usually arsenic derivatives, then helps kill the adult heartworms. About a month later, your vet will then administer microfilaria larvae treatments.  Either Ivermectin or Mylbemycin oxime is used and both are effective at eliminating heartworms.

Heartworm Testing

It is important for owners to know that DNA heartworm testing is available. As a responsible pet owner, you can test your dog for the presence of heartworms up to three times a year.

A study has found that the life cycle of the heartworm is temperature dependent, needing more than a month of above 57°F or 14°C, and two weeks of almost double that temperature. If a dog is exposed to heartworms under lower temperatures, one can be reassured that the disease cannot develop.  In other words, this heartworms is seasonal and dogs are safer in the winter months of most temperate locations.

Another important concern for owners: due to the aforementioned reasons, monthly administration of heartworm preventive medication is not necessary. This preventive measure has been overly advertised—and the threat has been emphasized—for companies’ financial gain. Furthermore, heartworms is not contagious from dog to owner. Only mosquitos can transfer heartworms, and they seldom develop in humans.

Heartworm Symptoms

Dogs with heartworms may show these symptoms, although sometimes the first symptom is heart failure:

  • Coughing;
  • Difficulties breathing and lack of desire to do physical exercise;
  • Nosebleed;
  • Pain: eyes, kidney and joints (due to tissue damage and inflammation).


Heartworm Treatment History

Concerning adulticides, Melarsomine dihydrochloride is most commonly used, and it is the only one approved by the FDA in 2015. Ivermectin, the treatment for microfilaria, was created in 1981 by William Campbell (Merck Institute, NJ) and Satoshi Ōmura (Kitasato University, Tokyo). As for Mylbemycin oxime, another microfilaria treatment, it is related to Ivermectin and was found in 1972.

The second mentioned compound is somewhat less potent than the first. Both compounds come from the Streptomyces hygroscopicus bacteria.

The heartworm disease (Dirofilaria immitis) itself originated in the southern United States. However, it has since expanded to other regions warm enough to sustain the parasite, including Canada and Alaska. Now, people report this parasite present on all other continents.

Heartworm Treatment Side Effects