Heartworm disease is a severe illness that can be fatal to dogs. It’s also a common condition among dogs. Data from the American Veterinary Medical Association, around 1 million dogs in the US had heartworm disease by the end of 2019.

While it’s been around for decades, there are still many misconceptions about how it spreads and how to prevent it. This article will explain how heartworm disease spreads in dogs so you can protect your pet from this dangerous parasite.

How Heartworm Disease Spreads in Dogs

Mosquitoes spread heartworm disease. The mosquito bites the dog and then transfers heartworm larvae to the dog’s bloodstream, where they grow into adult worms and lay eggs. The eggs settle in your pet’s lungs, heart, or arteries.

Hence, many areas alongside rivers had many cases of heartworms in dogs. According to 2022 data, the prevalence was between 4-100% in the area around the Mississippi river, the southern portions of the interior Midwest, and along the Atlantic coast towards the north, including Virginia and south New Jersey.

If you live where heartworm is expected, keep your dog on prevention year-round. If you move to a new place with no mosquitoes, talk with your vet about how long it would be safe for him or her not to take precautions against this disease.

However, it is always best to consult your vet and take the necessary precautions. It takes only a few months for heartworm larvae to grow into adults. The American Heartworm Society recommends giving your dog 12 months of heartworm prevention.

Heartworms’ life inside a dog is between 5 to 7 years. This disease is not contagious. Hence, your dog will not get heartworm if he or she comes in contact with some other dog having a medical condition. However, it can increase the chances. If another dog nearby has heartworm, the chances of a mosquito biting him and then biting your dog increases.

What Are the Signs of Heartworm Disease?

Heartworm disease symptoms in dogs can be hard to spot. The first sign of heartworm disease is often a cough, which can be mistaken for asthma or kennel cough. Other common symptoms include weight loss and lethargy, but many dogs don’t show signs until they’re very sick or die from heart failure.

If you suspect your dog has been infected with heartworms, it’s essential to take them to the vet immediately so that they can receive treatment before further damage is done and so that you know what steps you need to take next time around!

How Is Heartworm Diagnosed

A veterinarian can only diagnose heartworm disease, and several different types of tests can be used to diagnose heartworm. The most common test is the indirect immunofluorescence assay (IFA), which checks for the presence or absence of antibodies that indicate whether your dog has been exposed to heartworms in the past.

This test can be performed on either your dog’s blood or urine samples. If it shows up positive for antibodies against microfilariae, it indicates active infection with adult worms residing within his body cavity or lungs.

If you’re concerned about false negatives, talk with your veterinarian about additional testing options such as ultrasound examinations or x-rays. These might help them identify an adult female worm within their patient’s chest cavity before they start treatment, so they don’t miss any opportunities for treating an existing condition effectively while also preventing future complications like pulmonary hypertension syndrome (PHS).

How Is Heartworm Treated

If you’re reading this, it’s probably because your dog has been diagnosed with heartworm disease. While it’s a scary diagnosis, don’t be too alarmed. Treatment is effective if started early and can help your dog live longer.

To treat heartworm disease in dogs, a veterinarian will prescribe an oral medication that kills adult worms and larvae. There are many heartworm medicines for dogs, such as Heartgard Plus. These medicines have dewormer ingredients that can prevent heartworm larvae from growing.

If treatment stops before the entire course of medication has been administered, the remaining larvae can grow into adults and cause signs of illness again within six months or less! Hence, it is vital to take the given medication on time. According to an article published on the University of Florida’s website, dogs are cured only after two negative heartworm antigen tests, which must be done six months apart.

What Will Heartworm Do to Your Dog?

Heartworm is a severe disease that can be fatal to your dog. If you have a pet, you need to know how this disease spreads and how to prevent it from infecting your animal.

Heartworm affects the heart and lungs of dogs, cats, ferrets, foxes, and wolves. The worms are passed on through mosquitoes when they bite an infected animal. Once inside the body of an uninfected animal, these parasites make their way into its bloodstream, where they grow up to 36 inches long! Over time this causes significant damage inside their host’s body, including:

  • Fatigue/weakness
  • Loss of appetite
  • Weight loss
  • Difficulty breathing

How Is Heartworm Prevented

Heartworm prevention is a pill or chewable that can be given every month. It’s safe for all dogs, but there are some things you should know about how it works. Some heartworm preventatives have a different schedule. Talk to your vet about what works best for your pet.

The medication needs time to build up in the body before it’s effective against heartworms and other parasites. This means that if you start using one too late in summer when mosquitoes are active and likely carrying larvae, they may still get infected with worms even after taking the medication!

If you live somewhere warm enough, such as Florida or Texas, and plan on being outside during mosquito season, ask your vet whether using an insect repellent containing DEET would help protect your dog from getting bitten.

If you think this might happen anyway, ask whether adding another product called ivermectin would also help prevent infection. It’s important because of safety concerns and because some medications could interact poorly with each other or cause side effects if taken together.


Heartworm disease is a severe condition that can be fatal if left untreated. It’s essential to understand how heartworm spreads in dogs and how to prevent this illness from happening to your pet.