This Growing Threat Can Kill Your Pet From the Inside Out

Analysis by Dr. Karen Shaw Becker

lungworm in dogs

Story at-a-glance -

  • Lungworms can cause infection in both dogs and cats that occurs through exposure to a host animal that carries the parasite
  • Pets allowed to roam freely outdoors are at highest risk, including those who hunt and eat prey or drink from ponds or free standing water
  • Symptoms of infection depend on several variables; pets with mild or hidden infections show no symptoms
  • Treatment for lungworm typically includes an anti-parasitic drug; a protocol of natural therapies can be very beneficial as well
  • Especially in areas where lungworm infections are prevalent, it’s important to take common sense measures to reduce your pet’s risk of exposure

Recently I ran across a terribly sad story about a darling French Bulldog named Minnie who died suddenly after a routine veterinary procedure. Minnie, who lived with her family in Rugby, a market town in Warwickshire in the U.K., developed uncontrollable bleeding after the surgery.

As it turns out, she had an asymptomatic, undiagnosed lungworm infection. The lungworm parasite hides inside the heart and lungs, and among other problems, it interferes with the body’s blood clotting ability. Minnie’s heartbroken owner, Sian Reekie, told the Coventry Telegraph:

“I had never heard of lungworm before Minnie’s tragedy. We now know that it is often called a silent killer, this couldn’t be truer. Before her operation, Minnie was well and her usual cheeky self, little did we know that lungworm was secretly killing her inside. To say we are devastated to lose Minnie is an understatement.

We weren’t prepared for what happened to Minnie, we hope her story will help raise awareness of the parasite, as it is in the Rugby area and dog owners need to speak to their vets about how to prevent it.”1

Lungworm Geographic Range May Be Expanding

Lungworms are parasites that have the ability to infect the respiratory tracts — the lungs and windpipes (tracheas) of dogs and cats. There are several different parasites that fall into the category of lungworm. Some types infect dogs, some infect cats, and some can infect both dogs and cats.

Pets who roam freely outdoors in certain locations in North America and elsewhere are at highest risk of acquiring lungworm disease. The cat lungworm (Aelurostrongylus), for example, is found throughout the southeastern U.S. Experts believe the geographic range of lungworms may be expanding, which seems to be the case in certain areas of the U.K.

It’s also possible that heightened awareness by veterinarians is resulting in more testing for the pathogen, and consequently more diagnoses of infection.

How Dogs and Cats Can Become Infected

Lungworm infection typically occurs when a dog or cat is exposed to a host animal that carries the parasite. Pets who hunt and eat prey outdoors are at risk, as well as those who drink from ponds or free standing water that may contain the larval stage of the worm.

Once ingested, the worm larvae travel via the bloodstream out of the intestines to the lungs, where they grow into adult worms and lay eggs. In the case of the tracheal worm (Oslerus osleri), infection in dogs can be transmitted directly from the mother to her litter while she’s licking her pups, or if they come in contact with her infected feces.

Many lungworm parasites are found near lakes where crayfish, snails and slugs are hosts. Raccoons eat crayfish and snails, so a dog who comes in contact with a raccoon or raccoon poop can be exposed. Cats are more likely to be exposed when hunting birds or small mammals that have eaten infected snails. Significant lungworm infections are most often seen in heavily infested pets under 2 years of age.

While there are many species of lungworm that can infect an animal’s lungs, the most common parasite seen in dogs is the tracheal worm, Oslerus osleri. In cats, two of the most prevalent worms are Capillaria aerophila and Aelurostrongylus abstrusus.

Symptoms of a Lungworm Infection

Symptoms of infection depend on the specific type of parasite your pet has been exposed to, how long he or she has been infected, the severity of the infection and the immune system response to the presence of the parasites.

Animals with mild or hidden infections often have no symptoms, which was the case with poor Minnie, or they may experience some mild coughing, lethargy, exercise intolerance or weight loss. Symptoms associated with inhibited blood clotting include excessive bleeding from even minor wounds/cuts, nosebleeds, bleeding into the eye and anemia.

In severe infestations where there are large numbers of larvae in the airways, complications can include shortness of breath, bronchitis, emphysema, fluid build-up in the lungs and even pneumonia. Dogs that recover from lungworm disease are thought to have some level of immunity against future exposure. This is quite rare in that it doesn’t happen with other parasitic infections.

Diagnosing an Infection

Your veterinarian will take a complete medical history on your pet and perform a physical exam that will include listening to the lungs with a stethoscope. A complete blood count (CBC) and chest X-rays will be needed, along with a fecal exam to check for the presence of worm ova or larvae.

Respiratory secretions will also be checked for ova or larvae, using a procedure called a transtracheal wash. In addition, a test will be performed to rule out heartworm disease.

Since lungworm infections can masquerade as other common diseases, including pulmonary toxoplasmosis, respiratory mycoses and feline asthma in cats, it’s important to get an accurate diagnosis. Dr. Kathryn Primm, writing for dvm360, offers the following guidance to veterinarians:

“In any cat presented for evaluation of signs suggestive of respiratory disease, lungworms should be considered. To better find lungworm infections, veterinarians should consider a Baermann fecal migration technique for stool sample examination, be watchful for trichurid eggs in any feline fecal sample, and be careful to discern between whipworm and capillarid infections.”2

Treatment Options

The traditional treatment for lungworm is an anti-parasitic drug. Integrative veterinarians also use beneficial adjunctive remedies that help reduce inflammation in the airways, including ozone therapy, essential oil inhalation therapy (the protocol designed by a veterinarian trained in using essential oils this way), oral cat’s claw and turmeric. Rechecking your pet’s stool samples is an important step in ensuring the lungworm infection has been completely resolved.


Lungworm is currently a bigger problem in the U.K. than in the U.S., but it makes sense to take common sense precautions to prevent exposure no matter where you and your pet live.

Since it’s primarily free-roaming dogs and cats who are exposed to lungworm, the most important preventive step you can take is to ensure your pet is supervised and under your control at all times when outdoors. Don’t allow your cat to hunt prey, don’t let pets drink from ponds or other freestanding bodies of water and keep dogs away from parasite hosts such as crayfish, snails and slugs.

U.K. veterinarians are recommending monthly broad-spectrum dewormer products. Due to the potential for side effects and toxicity, my recommendation is to avoid such products and instead, take appropriate common sense steps to reduce or eliminate your pet’s risk of exposure to the parasite, and check a fecal sample every six months for the presence of the parasite.