How Are Heartworms Treated?

The incidence of heartworm is decreasing due to the increase in use of monthly heartworm preventative medication

Fortunately, with the increase in use of monthly heartworm preventative medication such as Sentinel or Heartgard, and/or natural herbal alternatives such as black walnut or quassia bark, the incidence of heartworm disease is decreasing. However, in stressful situations and/or in immune or nutritionally compromised patients, heartworm disease is still being diagnosed in most states. In decades past, heartworm was typically treated with a strong arsenical compound known as Caparsolate intravenously in the veterinary hospital setting. Side effects were common, including inflammation of the blood vessels (known as phlebitis) at the site of injection, as well as sometimes systemic signs including vomiting, diarrhea, coughing, liver/kidney complications, and even acute sudden death.

In recent years, veterinarians are using a safer more modern alternative known as immiticide which is typically given as a series of once-daily intramuscular injections over a few days. While the above side effects may still occur, the incidence of negative reactions is much reduced. During the month of treatment with immiticide, many heartworm positive dogs will also be treated with the antibiotic Doxycycline, which will kill other parasites known as Wolbachia, as well as decrease inflammation and the development of secondary bacterial infections.

In those pets that are geriatric or sick with other illnesses, some veterinarians will use monthly Sentinel or Heartgard in not only preventing heartworm infection, but in preventing the further development of heartworm larvae and microfilaria (baby heartworms) in heartworm positive dogs. When used in this fashion, after a period of 1-2 years of continuous monthly heartworm prevention use, many heartworm positive dogs will become negative. During that time it is important to restrict exercise and to monitor for rare side effects that dying heartworms may have on the body.

On the other hand, holistic veterinarians will work on strengthening the immune system of the pet through diet and nutritional supplementation with herbs including quassia bark, black walnut and hawthorne. Based on the individual constitution of the patient, homeopathic remedies also may be prescribed, which will help decrease susceptibility to secondary organ damage and systemic risk, in hopefully stimulating the pet’s ability to clear the heartworms on their own. No matter which approach is used, some form of conventional or natural heartworm preventative should be used to prevent re-infection in the future.

Related Posts


  1. I was really interested in reading about heartworm since my rescue dog, Dante tested positive prior to me adopting him. Someone else had adopted him, but left him there after hearing it would cost $800 to cure him. Thank goodness the shelter took him back and paid the vet bill. Can’t say enough about the Bridgeport shelter where I got him. I’ve had him for 5+ years and he’s been my steadfast friend throughout some very difficult times. I can’t imagine life without him. I feel sorry for the man who left him at the vet, he’ll never know what he’s missed out on.

  2. Dr. Michael Dym, VMD veterinarianMay 11, 2012 at 9:19 pm

    Thanks for sharing.

  3. I am enduring my secind dog dying because of heartworms. They were both on preventive and contacted these evil worms anyway. it is so discouraging

  4. Dr. Michael Dym, VMD veterinarianSeptember 23, 2013 at 9:53 am

    I am so sorry Sylvia to hear of your dogs. Most of time monthly heartworm prevention is highly effective. There are isolated cases now being reported of resistant heartworms. Hoping that does not continue

Leave a Comment