Lungworms in Dogs

Slugs and snails are the carrier of lungworm larvae. Infection of your dog can occur by accidental or purposeful ingestion of the gastropod, and also by the transmission of larvae through the feces or saliva of infected dogs. Frogs are also believed to carry the parasite. Though death by lungworm is not common, it is known to be a risk as the result of infection. Younger dogs are more often to be found infected, and it has been noted that Cavalier King Charles Spaniels and Staffordshire Bull Terriers are represented the most frequently in studies.

The scientific name for lungworm is angiostrongylus vasorum. Infection with this parasitic nematode can present with a number of complications. Studies have shown the lungworm to be the cause for inflammatory reactions in the lungs, with severe consequences for many areas of the canine body, including congestive heart failure.

Though it has been noted that some dogs may be asymptomatic when infected with lungworm, two signs of infection that are most apparent are a chronic cough and respiratory strain upon exercise. Other symptoms may be:

• Gagging
• Vomiting
• Loss of appetite
• Weight loss
• General malaise

In cases where the infection has progressed, severe respiratory distress and heart failure can occur. With migration of the larvae in various stages including adult lungworm throughout the body, damage to the brain, spinal cord, organs and more will be displayed with varying symptoms, according to the location of the infection.

The lungworm is able to enter and multiply in the host, which is your dog, upon ingestion of third stage larvae. The third stage larvae then penetrate the gut wall and develop in the lymph nodes before entering the circulatory system. Adults of both sexes can then be found in the pulmonary circulatory system and the right ventricle. The worm will mature in the lungs, finally mating and lodging in the capillaries. With advanced stages of infection, it is often discovered that the lungs contain inflammatory nodules filled with eggs and larvae. Adult nematodes are seen in the capillaries, as well as the pulmonary arteries of dogs in the advanced state of disease. Cases are most often found in winter and spring, due to the abundance of gastropods found in the summer, with the disease developing over the next few months.

Diagnosis of angiostrongylus vasorum is not easily reached. Because of the absence of definitive clinical signs, dogs may remain infected and untreated, which can, unfortunately, lead to advanced degrees of disease severity. Dogs with this infection may present with signs of bleeding disorders and heart or lung disease. However, coughing is considered a sign of lungworm infection, which will be indicative to the veterinarian as to how best proceed in the diagnostic phase of the visit.

If the veterinarian does suspect that your pet in infected with lungworm, she will ask for a stool sample to be brought to the clinic. Several samples of fecal matter must be analyzed due to the fact that the presence of larvae in the feces may be intermittent. This diagnostic tool is considered the best option, with the procedure being called the Baermann test. The test is usually read after 8 hours, but in heavily infected dogs, results can show as positive after as little as 30 minutes.

X-rays may show lesions on organs or density in areas of the lungs, and blood work may show signs of anemia and clotting disorders. A bronchoscopy may be necessary in order to examine the washings for evidence of white blood cells, eggs, and larvae.

The treatment of lungworm in dogs will depend on the stage of the infection. Canines in the advanced phase of the illness will have a lower prognosis of recovery due to the possibility of damage to the heart and other organs such as the pancreas and kidneys, as a result of the presence of the lungworm throughout the body. However, success has been attained, and dogs with severe infection are given medication to destroy the lungworm and are then treated with corticosteroids to heal damaged lungs. The use of a bronchodilator is sometimes used in cases of pneumonia. At times, surgery may be needed in order to remove nodules.

An infection caught early can be treated with medication alone; however, it must be noted that the treatment is extensive, with the prescription being given four (4) times minimum, one week apart. Treatment may be to be repeated, or continued for two months.

Dogs who have gone through treatment for severe infection of lungworm will have a longer recovery period than a dog where treatment was given in the early days of infestation. Depending on the severity of symptoms at the time of diagnosis, and the advancement of the lungworm infection, most pet owners can expect a positive outcome for their dog.

In the case of a heavily infected pet who may have shown signs of respiratory distress, recovery will include rest, medication and perhaps a bronchodilator. Expectorants and diuretics may be used post-treatment as well to combat the effects of the lungworm on the body. Shortness of breath may occur throughout the healing process.

Monthly year-round treatment may be prescribed to prevent reinfection.