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Overview of Feline Lungworms

Lungworms are an example of a parasite (“worm”) that can infect the respiratory tract of cats. There are several different parasites that have been identified including: Aelurostrongylus abstrusus, Paragonimus kellicotti and Capillaria aerophilia.

Outdoor cats 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. For example, the cat lungworm (Aelurostrongylus) is found throughout the southeastern USA. Cats acquire the infection when they eat the snails or slugs that act as the intermediate host and (more likely) the birds or small mammals that eat the infected snails. Thus, a “hunting” or outdoor cat is most likely to be infected.

The lung fluke (Paragonimus) is found near lakes that harbor the intermediate host (crayfish and snails) or the raccoons that eat them.

Clinically important infections occur most often in younger cats (those less than 2 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 of Lungworms in Cats

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

  • Complete medical history and physical examination including lung auscultation (stethoscope examination).
  • Thoracic (chest) radiographs (X-rays).
  • Fecal 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 of Lungworms in Cats

  • If lungworms are diagnosed, an anti-parasite drug must be given. Often these are the common “dewormers” used for roundworms, hookworms and tapeworms, but at different doses for each.  
  • If there is severe reaction to the parasite, an anti-inflammatory dose of corticosteroids may be needed for a brief period (3 to 10 days).
  • Home Care and Prevention

    In addition to careful observation, you may be asked to medicate your cat 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. Some are liquids, other pills.

    The only effective preventative is to control the roaming and hunting of cats allowed outdoors.

    In-depth Information on Lungworms in Cats

    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:

  • Aelurostrongylus abstrusus affects cats and during its lifecycle its intermediate hosts are the snail and slug and its transport hosts are birds, small mammals and reptiles. Its geographical distribution is worldwide.
  • 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.

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

  • Airway obstruction (foreign body, tumor)
  • Asthma
  • Bronchitis
  • Respiratory infections
  • Heartworm disease
  • Heart disease (coughing can occur in cats, but is not as common as in dogs)
  • Allergic lung diseases
  • Pneumonia
  • Pulmonary granulomatosis (type of inflammation)
  • Pulmonary neoplasia (lung cancer)
  • In-depth Veterinary Care of Lungworms in Cats

    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.
  • Feline leukemia (FeLV) test and FIV (feline AIDS virus) test
  • 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 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.
  • Aelurostrongylus abstrusus Treatment

  • Fenbendazole (Panacur) for 10 days
  • Ivermectin for 3 days to 5 days.
  • Paragonimus kellicotti Treatment

  • Fenbendazole (Panacur) for 10 days
  • Praziquantel (Droncit) every 8 hours for 2 days
  • Albendazole every 12 hours for 10 to 20 days
  • Ivermectin two treatments, 2 weeks apart
  • Capillaria aerophilia Treatment

  • Fenbendazole (Panacur) for 10 days
  • Albendazole for 10 to 20 days
  • Ivermectin one or two doses
  • Home Care for Feline Lungworms

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

    Minimize chance of reoccurrence by eliminating exposure to host. Prevent your cat from predatory (hunting) or scavenging infected crayfish or snails.

    Repeat Chest X-rays are suggested in about two and 4 weeks to assess improvement. Recheck a fecal sample to monitor for further development of larvae or ova in 2 to 4 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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