Lung Worms



Lungworms are a type of parasite that can infect the respiratory tract.

There are several different parasites that have been identified including:

Paragonimus kellicotti, Capillaria aerophilia, Filaroides and Osleri spp.

Outdoor pets in certain geographic areas of North America and elsewhere are predisposed to respiratory parasites. Infection typically occurs from exposure to the hosts that carry the parasite.

The lung fluke (Paragonimus) is found near lakes that harbor the intermediate host (crayfish and snails) or the racoons that eat them. Dogs that hunt and eat raccoon meat may be at risk.

The tracheal (windpipe) worm Osleri osleri is directly transmitted from the mother to pup.

Clinically important infections occur most often in younger animals, those less than two years old, that are heavily infested. The symptoms for lungworm infections depend on the specific parasite, the severity of the infection and the host response. Some pets with mild infections are normal, while other pets will exhibit a cough, lethargy, exercise intolerance and weight loss.

What to Watch For

Coughing is the most common sign of lungworm infection.

Diagnosis

Veterinary care should include diagnostic tests and subsequent treatment recommendations. Diagnostic tests are needed to recognise lungworms, and exclude other diseases. Tests may include:

  • Complete medical history and physical examination including lung auscultation (stethoscope examination)
  • Thoracic radiographs (chest X-rays)
  • Faecal examination must be done to check for ova or larvae. A special technique called the Baermann technique may be required.
  • Examination of respiratory secretions should be done to check for ova or larvae. These secretions may be obtained by a procedure called transtracheal or endotracheal wash.
  • A heartworm test should be performed to exclude this disease.

Treatment

If lungworms are diagnosed, an anti-parasite drug must be given. Often these are the common "dewormers" used for roundworms, hookworms and tapeworms in dogs.

If there is severe reaction to the parasite, an anti-inflammatory dose of corticosteroids may be needed for a brief period, usually three to 10 days.

Home Care and Prevention

In addition to careful observation, you may be asked to medicate your pet for this condition. This can be a challenge in some cases and you should ask for help at your veterinarian's office if you need directions regarding proper medication techniques. A variety of medications may be prescribed depending on the exact parasite identified and are in the form of liquids or pills.

The only effective preventative is to control the roaming and hunting of dogs allowed out-of-doors. In the case of Osleri osleri infection, the bitch (mother) should also be treated for the tracheal worm.

Section: Information In-depth

Infection of the respiratory tree is in some ways similar to infection of the stomach and intestines by gastrointestinal parasites like roundworms or hookworms, although it is less common. The lungworm injures the airways or lung tissue by inciting an inflammatory reaction. The parasites live and reproduce in the respiratory tissues.

Dogs acquire lungworms by eating one of the "hosts" that serve the lungworm during part of its life cycle. The life cycle of the different parasites can be complicated, involving both intermediate hosts and transport hosts.

The summary of specific lugworms parasites, the species each affects, the lifecycle of each and the geographical distribution of each is as follows:

Paragonimus kellicotti affects dogs and during its lifecycle, the intermediate hosts are the crayfish and snail. The transport host is the raccoon. The geographical distribution is North America.

Capillaria aerophilia has a direct lifecycle. Its geographical distribution is North America.

Osleri and Filaroides ssp. both affect dogs and each has a direct lifecycle.

The geographical location of each is worldwide.

The major symptom of lungworms is coughing. Of course, there are numerous causes of cough or other signs similar to lungworms. Some common examples include:

  • Infectious tracheobronchitis
  • Tracheal collapse
  • Airway obstruction (foreign body, tumor) Bronchitis Respiratory infections Heartworm disease Heart disease Allergic lung diseases Pneumonia Pulmonary granulomatosis (type of inflammation) Pulmonary neoplasia (tumors) Hepatopulmonary migration of enteric worms (intestinal worms, such as roundworms, spend time migrating through the lungs and liver in younger dogs)

Section: Veterinary Care In-depth

Veterinary care should include diagnostic tests and subsequent treatment recommendations.

Diagnosis In-depth

Diagnostic tests are needed to recognize lungworms and exclude other diseases. Tests may include:

A complete medical history and physical examination

  • Thoracic radiographs (chest X-rays) to exclude other causes of coughing.
  • Some lungworm infections lead to characteristic or suggestive changes in the lungs.
  • Fecal examination for ova or larvae. These are not your typical intestinal worms and special methods called sedimentation techniques may be needed to find the microscopic ova (eggs) or offspring (larvae).
  • A heartworm test should be done to exclude the presence of intestinal worms because the symptoms are similar.

Additional diagnostic tests may be recommended on an individual pet basis, including:

Examination of respiratory secretions for ova or larvae. These secretions may be obtained by a procedure called a transtracheal or endotracheal wash.

Sterile fluid is flushed into the lungs using a catheter. This may be done by local anesthetic in larger dogs, or under brief anesthesia in puppies or active dogs. Your veterinarian can discuss this with you if the suspicion for lungworm infection is high.

Bronchoscopy. A small soft flexible fiber optic tube is inserted into your pet's airway to allow examination within the windpipe and bronchial tree in this procedure. Certain parasites like Osleri osleri can be identified visually by this method. Furthermore, a number of problems not evident by X-rays may be seen, including laryngeal (voice box) diseases, polyps, foreign materials such as pieces of inhaled plant material, wood, bone, and some tumors. Samples of fluid from the lungs and bronchial tree can be examined under the microscope and fluid can be cultured for infection. This is especially useful with undiagnosed cases of cough.

A complete blood count (CBC) to check for signs of infection and to identify an increase in eosinophils. This cell type is often increased in parasitic infections.

Blood biochemistry tests should be normal in the case of lungworms. However, this test may be done if general anesthesia is planned or generalized illness is observed.

An echocardiogram (cardiac ultrasound) to rule out heart disease

Therapy In-depth

The principles of therapy for lungworms include killing the parasite and reducing tissue reaction if necessary. Most treatments are done on an outpatient basis or involve a very brief hospitalization. Treatments may include:

Treatment of tissue inflammation with prednisone </articles/artShow.asp?artID=1553> for 5 to 10 days with expected side effects of increased water consumption, urination and appetite

Treatment of the parasite by killing it with an anti-parasitic drug. Some of these like fenbendazole are very safe. Others (high dose ivermectin) are more likely to cause side effects in about 5 to 10 percent of pets.

Drugs recommended for the different parasites include:

Paragonimus kellicotti (dog lung fluke)

  • Fenbendazole </articles/artShow.asp?artID=1505> (Panacur®) for 10 days Praziquantel </articles/artShow.asp?artID=1554> (Droncit) every 8 hours for 2 days
  • Albendazole every 12 hours for 10 to 20 days Ivermectin </articles/artShow.asp?artID=1525> two treatments, 2 weeks apart (NOT IN COLLIES or in animals of uncertain heartworm status)

Capillaria aerophilia (the "fox lungworm" that can affect the dog)

  • Fenbendazole (Panacur) for 10 days
  • Albendazole for 10 to 20 days
  • Ivermectin one or two doses (avoid in collies or in animals of uncertain heartworm status)

Filaroides spp

  • Fenbendazole (Panacur) for 10 days
  • Albendazole for 10 to 20 days
  • Ivermectin one or two doses (NOT IN COLLIES or in animals of uncertain heartworm status)

Section: Follow-up

Optimal treatment for the pet with lungworms requires a combination of home care and professional veterinary care. Follow-up can be critical. Administer all prescribed medication and be certain to alert your veterinarian if you are experiencing problems treating your pet.

Minimize the chance of reoccurrence by eliminating exposure to host. Prevent your pet from hunting or scavenging infected crayfish or snails.

Repeat chest X-rays are suggested in about two and four weeks to assess improvement. Recheck a fecal sample to monitor for further development of larvae or ova in two to four weeks.

The prognosis is good for full recovery, unless the problem has been ignored or untreated for many months (or years), in which case permanent lung scar tissue may form. If severe changes have occurred to the lungs, a residual cough may be present.

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