Working in dog rescue, we see more than our fair share of heartworm positive dogs. We also get numerous questions related to heartworms and myths about heartworm infection. So, I thought I would do a write up on the topic and hopefully help arm you with knowledge. If you have questions that aren’t answered here, please ask. If I do not know the answer, I will find it for you. Near the end of this post I will share a very affordable treatment and prevention option for heartworms. I am NOT a vet. Please check with your vet before changing or starting any medications or preventative measures.

Dogs get heartworms from the bite of an infected mosquito. There is no way to tell if a mosquito is infected and it only takes ONE bite. This is why prevention is so important. It takes approximately 7 months, after being bitten by an infected mosquito, for the larva to grow into an adult heartworm. The adults reside in the heart, lungs, and nearby blood vessels where they begin to reproduce. An adult heartworm can be up to 12 inches long and live for up to 7 years. Dogs can be infected with HUNDREDS of heartworms at once.

Humans cannot get heartworms from their dog. The bite of infected mosquitoes is the only method of transmission. Pets will not give heartworms to other pets. In RARE cases, humans can become infected (if bitten by an infected mosquito). However, the heartworm cannot complete its life cycle in the human body. Again, a human becoming infected is extremely rare.

It is perfectly safe to adopt a dog with heartworms. Most shelters do not have the money to treat the disease so these dogs need a dedicated owner, or foster family. If a dog has not had a full pre-treatment workup, you are looking at a cost of up to $1000 to treat your dog. The treatment alone can run around $300-$500. An arsenic-based injection is given to kill the worms. Dogs must be kept calm and quiet as much as possible during and for the few months following treatment. As the heartworms die, they break apart and can cause blockages in the arteries. Most dogs that die after heartworm treatment do so because they are overly active during this critical period. However, one has to believe that arsenic is not healthy!

Prevention is key. Prevention is also much cheaper than treatment. Ask your vet what is best for your dog. Depending on the dog’s size, you will spend up to $100 per year on prevention. If the cost is too great, discuss the use of Ivermectin with your vet. This can be purchased at most feed stores for $5 or less. Please do not try to use this method without speaking to your vet. The dosing is very tricky and you don’t want to do more harm than good.

If you suspect your dog has heartworms, get them to the vet immediately to begin a workup and treatment. Ivermectin can be used as a treatment as well. Again, I urge you to talk to your vet before using this product. Symptoms or heartworm infection can include a cough, easily tired, lethargy, and fluid retention. Once these signs are present, the infection is serious and needs immediate attention. Without treatment the dog will suffer greatly and die.

Now, to dispel a few myths about heartworms.

  • Dogs can get heartworms ANY time of year. Do not skip their preventative treatment, even in colder months.
  • Dogs DO NOT outgrow heartworms.
  • Once a dog has heartworms and has been treated they are NOT immune. They can have repeat infections if the proper preventative method is not used.
  • Heartworm cases have been seen in ALL 50 states…even where it was once thought that heartworms weren’t present.

Again, I am not a vet. These are things that I have learned over the years and wanted to share with you. This information should not be used to diagnose or treat illness in your dog. If you suspect your dog is ill, take them to the vet. If you have any questions about this information or about heartworms, leave me a comment and I will get back to you ASAP.