All About Heartworm

Before beginning the article, I want to state that I am not a veterinarian or veterinary technician. I have not received formal education on animal medicine; therefore, please take everything with a grain of salt and speak with your veterinarian. I have a bachelor’s degree in environmental science and health, and part of my education was studying disease prevention. Therefore, there is some jargon in this article that skews medical. I hope to be clear when explaining the complex parasitic lifecycle. Everything written in the article is in my understanding of heartworm. If you are interested, I suggest reading other articles to paint a bigger picture. With that being said, I believe heartworm preventative should be a basic of dog ownership.

What is heartworm?

Heartworm is a parasitic roundworm that is transmitted via mosquitos. It is crucial to note that the three genera of mosquitos present in the U.S. are all able to transmit the heartworm microfilaria (Aedes, Anopheles and Culex). This means that any mosquito can transmit the parasite. The microfilaria is basically baby heartworms. They enter the dog’s body through the bite of a carrying mosquito. Once in the body, microfilaria matures into the larva, and the larva travel to the heart and lung tissues to sexually develop. From here the mature heartworms live in the lung and heart tissues, primarily in the pulmonary artery that carries deoxygenated blood to the lungs. The microfilaria is present within the blood of the dog as soon as six months after the initial bite. From here a mosquito can bite an infected dog and carry the parasite into another host. (American Heartworm Society)

Who is impacted?

Heartworm is zoonotic meaning it can transmit from one species to another. It is very rare for heartworm to mature in humans. Yet, many other mammals can get heartworms such as sea lions, tigers, foxes, raccoons or coyotes.

What are the symptoms?

One of the hardest parts of heartworm diagnosis is that heartworms usually do not present symptoms until months into the parasitic lifecycle within the dog’s body. Most veterinarians will do annual or biannual blood tests which include a heartworm screening. The test only requires a couple drops of the dog’s blood; however, false negatives are not uncommon because it takes about six months for the microfilaria to appear in an infected dog’s blood. Therefore, a dog living with heartworm can test negative if the roundworm microfilaria entered the body less than six months prior. Most of the symptoms of heartworm are common with other illnesses. Dogs may present symptoms such as lack of appetite, lethargy, coughing or difficulty breathing. Due to the commonality of the symptoms, the best way of checking for the parasite is via frequent blood tests.

What does treatment look like?

Heartworm treatment is a risky and long process. Since the roundworms live within the lung and heart, it creates a lot of strain on the animal’s respiratory and cardiac function. The way to treat heartworm is duel sided by killing the adult worms and the microfilaria. As the dog undergoes treatment, the dead worms are being broken down and discarded. This process can be very strenuous on the dog’s body. The owner is looking at months of exercise restriction and costly veterinary intervention. In severe cases, the dog may need to undergo surgery to remove the roundworms.

Does geography play a role in prevention?

As mentioned, mosquitos are the means of transmission for heartworm. But, not everywhere has mosquitos, so how does this impact prevention? First, I suggest speaking with your veterinarian because they know your region best. However, even in California which is not a huge mosquito region, Bee was advised to be on preventative. The most important fact of geography, in my opinion, is one that I read in my favorite puppy book Puppy’s First Steps: A proven approach to raising a happy, healthy, well-behaved companion by the faculty of veterinary medicine at Tuft’s University. The book states, “dogs at the highest risk for heartworm are those taken from a non-heartworm area, such as California, and transported to a high-heartworm area” (Dodman & Linder, 2007, p. 66). This is crucial to understand because if you choose to move with your dog, you may be putting them at higher risk; therefore, you need to take extra precaution.

How to be a responsible dog owner regarding heartworm

Prevention is key. The best way to protect your dog from heartworm is through responsible and regular protection methods. In today’s veterinary field, there are many options for heartworm prevention thereby enabling owners to pick the best option for their lifestyle. The most common form of prevention is a monthly dosage of heartworm preventative such as Heartguard or Interceptor. You can research the difference between the two preventative products, but the main difference is that Interceptor protects against tapeworms and whipworms on top of roundworms. In my research, the prices are comparable. Something to note with monthly dosages is that mosquitos are not present year-round in some areas. Your veterinarian may give you the option to only give preventative during mosquito months. However, I recommend you not decide this tactic on your own because even in New England veterinarians recommend year-round protection. For me and Bee, we give monthly heartworm preventative year-round because it is easier to remember and he travels. If remembering a monthly dose does not work with your lifestyle, you can opt for a shot. The ProHeart 6 shot provides heartworm protection for a full six months. However, the shot does have some potential side effects; therefore, as always, you should discuss your options with your veterinarian. The shot is useful for people that struggle to remember to give the monthly dosage. Whichever option you choose, my suggestion is to choose a heartworm preventative if you can afford the cost. It is your responsibility as a dog owner to do everything within your means to protect your dog. Heartworm preventative is a basic that will keep your dog from contracting an extremely dangerous and fatal parasite. I urge you to start a conversation with your veterinarian if your dog is not taking heartworm preventative.