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Pet Owner Version

Lungworm Infection in Cats


Lora Rickard Ballweber

, DVM, DACVM, DEVPC, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University

Reviewed/Revised Aug 2018 | Modified Oct 2022

Lungworm infection of the lower respiratory tract, usually resulting in bronchitis or pneumonia, can be caused by any of several parasitic nematodes (roundworms), including Aelurostrongylus abstrusus and Eucoleus aerophilus in cats. Aelurostrongylus abstrusus is normally transferred to cats after eating a bird or rodent that has previously eaten a slug or snail containing the worms. Eucoleus aerophilus in cats has a direct cycle, with infective eggs being consumed along with food or water.

Signs of lungworm infection range from moderate coughing with slightly increased breathing rates to severe, persistent coughing, labored breathing, and respiratory distress or failure. Infections with no visible signs can also occur. Deaths are relatively uncommon with these infections, although they do occur in kittens.

Diagnosis of lungworm infection is based on signs, known transmission patterns, and presence of larvae in feces. Examination of the airways with an endoscope (bronchoscopy) and x-rays can be helpful tools. It can be a challenge for the veterinarian to diagnose lungworm because infected animals do not always pass the larvae in their feces, and when they do, they may be few in number. In cats, because of the relative infrequency of infection, diagnosis may be made only after failure of antibiotic therapy to improve the condition.

Lungworm infections can be difficult to treat, but there is evidence that appropriate antiparasitic drugs are effective. It may be necessary to continue antiparasitic treatment for up to 2 months.

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