Lower Respiratory Parasites in Dogs

Key takeaways

Respiratory parasites are tiny organisms that infect the respiratory tract of dogs, and are spread through feces or contact with an infected animal. 

  • These parasites live in a host’s lungs, trachea, or airways, and may lead to symptoms such as coughing, rapid breathing, and lethargy
  • Infections are rarely fatal, but may lead to difficulty breathing or, in severe cases, heart failure or respiratory distress
  • Diagnostics include a physical examination, bloodwork, fecal examination, diagnostic imaging, and a bronchoscopy
  • Infections are treated with targeted anti-parasitic medication, usually requiring multiple applications
  • Prognosis for respiratory parasites is usually good, although chronic lung damage may occur
  • Prevention methods vary, but proper hygienic care and preventing dogs from consuming small prey and aquatic species dramatically reduce susceptibility
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A closer look: Lower Respiratory Parasites in Dogs

There are multiple species of respiratory parasites that can affect dogs.

Lungworms are large roundworms which live within the lung tissue.

Tracheal worms are roundworms that live in a dog’s windpipe.

Lung flukes are flat, leaf-shaped parasites found in lung cysts.

Bronchial Worms are roundworms that live in a dog’s windpipe or bronchi (the branching airways inside the lungs).

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Risk factors

The rate of respiratory parasite infection in dogs varies depending on living conditions, life habits, and geographical region. Most dogs living in a sanitary living environment with a controlled diet are unlikely to contract an infection. Dogs living in dense populations, such as kennels and breeding operations, are at higher risk.

Respiratory parasites are rarely fatal, although chronic symptoms like coughing or lethargy warrant prompt veterinary examination. An immunocompromised dog is more at risk of developing severe symptoms.

Dogs with respiratory distress such as difficulty breathing or severe coughing episodes require emergency medical attention.

Possible causes

There are several types of respiratory parasites that can infect dogs, and which are acquired through different means.

Lungworms are transmitted between dogs when larvae pass in an infected animal’s feces. Infected stool can contaminate dirt, cages, blankets, fur, and water. A common infection route is via a dog licking dirt from their fur after playing outside, or drinking from a contaminated water source.

Tracheal worms also pass through fecal contamination, but can also transfer through regurgitated food or saliva. An infected mother can transfer parasites to her pup through regular grooming behavior.

Lung flukes pass with feces and infect snails. Snails infect crayfish or crabs, and these may infect dogs if they are consumed.

Bronchial worms infect a dog through fecal contamination, or through consumption of an infected snail.

Main symptoms

Infected dogs are often asymptomatic.

Testing and diagnosis

Diagnostics include:

  • Physical examination
  • Diagnostic imaging
  • Bloodwork
  • Fecal examination
  • Bronchoscopy

Steps to Recovery

Respiratory parasites are usually treated with targeted oral antiparasitic medication. It is important to follow veterinary direction while treating parasitic infections, as repeat applications are usually necessary within a period of days to weeks. Inconsistent or delayed treatments are less likely to be curative.

In some cases antibiotics or supportive steroids may be indicated.

Prognosis for respiratory parasites is usually good, although chronic lung damage may occur. Dogs with chronic lung damage may show signs of exercise intolerance.

Medication targets parasites inside the host’s body but does nothing to prevent reinfection from the environment, so recurrence is possible.


Prevention of respiratory parasites varies, depending on the organism. Proper hygienic care is essential, as many pass with fecal matter. Keeping a sanitary living and play environment dramatically reduces the risk of infection. Bathing a dog may also wash unhatched larvae or eggs from their fur before parasites can migrate into the body.

Some respiratory parasites require an intermediate host, such as a snail, crab, or slug. Preventing a dog from eating these aquatic species prevents associated infections.

Are Lower Respiratory Parasites in Dogs common?

The rates of occurrence of respiratory parasite infection in dogs varies according to the geographic range of the parasite species.

Fecal- or saliva-based contamination is more likely to occur in densely populated locations, such as a dog park or a kennel.

Typical Treatment

  • Antiparasitic medication, used as directed
  • Antibiotics
  • Supportive corticosteroids

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