The most important nematode affecting the respiratory system of domestic cats worldwide is the lungworm, Aelurostrongylus abstrusus. Cats may become infected by ingesting intermediate hosts such as snails or slugs, but more likely infection is due to preying on hosts such as birds, frogs, lizards, snakes and rodents. Another respiratory parasite, Capillaria aerophila, is a nematode living in the trachea, bronchi, and bronchioles of wildlife and domestic carnivores. More recently, species of mollusk-borne nematodes from the Troglostrongylus genus have been identified as agents of verminous bronchopneumonia in cats. These parasites had been considered to be found only in wild cats, but now have been described in domestic cats from Mediterranean countries.
This study’s goal was to retrospectively describe clinical, radiographic and therapeutic features of lungworm infection in cats. The medical records of 26 cats diagnosed with lungworm were reviewed and included in the study. Cats were diagnosed by positive results at microscopic examination of feces (classical fecal flotation with zinc sulfate and with the Baermann-Wetzel technique), a complete radiographic analysis of the thorax and a complete post-treatment follow-up.
Results indicated that cats with single infections by Aelurostrongylus abstrusus (n=15), Troglostrongylus brevior (n=3) and Capillaria aerophila (n=1) and coinfections by T brevior/A abstrusus (n=6) and T brevior/C aerophila (n=1) were diagnosed. The most common signs demonstrated were respiratory and in descending frequency: coughing, breathing difficulties, tachypnea, abdominal breathing, ocular and/or nasal discharge and sneezing. Lung auscultation revealed increased vesicular breath sounds and adventitious sounds, such as wheezing and crackles. Other signs noted were anorexia, hyporexia, lethargy, weight loss and pyrexia. The most common laboratory abnormality was a mild normocytic, normochromic anemia. The radiographic changes noted were interstitial (n=24), bronchial (n=21), alveolar (n=10) and vascular (n=2).
Oral fenbendazole administered for three consecutive days led to clinical, radiographic and infection resolution. A variety of compounds, such as moxidectin, emodepside, milbemycin oxime, eprinomectin showed promise against T brevior and C aerophila. Further studies are warranted in regards to these compounds in the future treatment of lungworms.
In conclusion, lungworms should be included in a differential diagnosis in cats living in an endemic area and present with respiratory signs and respiratory abnormalities. Respiratory signs can be severe, especially in younger cats or kittens. Fecal microscopic examination should be one of the first steps in diagnosing cats at risk of lungworm infection. In most situations, timely treatment with a variety of anthelmintics leads to recovery.
