Equine Multinodular Pulmonary Fibrosis

Pneumonia (lung inflammation) in horses can be quite serious, particularly the recently described form termed equine multinodular pulmonary fibrosis. At the 2009 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas, Nev., one veterinarian discussed his experiences with the diagnosis and treatment of five cases of the disease in horses.

Equine multinodular pulmonary fibrosis results in damage and fibrosis of the tissues of the lungs in a characteristic nodular pattern, explained Rodney Belgrave, DVM, MS, Dipl. ACVIM, with the Mid-Atlantic Equine Medical Center in Ringoes, N.J. Equine herpesvirus-5 (EHV-5) has been implicated in this disease, he noted.

"These five cases of equine multinodular pulmonary fibrosis presented to us from 2004-2007; their ages ranged from eight to 16 years, and they originated from different barns," recalled Belgrave. "In each case, they were the only ones in their barns affected. They were all referred because of fever and weight loss that did not respond to antibiotic therapy."


Dr. Belgrave discusses equine multinodular pulmonary fibrosis.
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All cases had EHV-5 detected via DNA or polymerase chain reaction (PCR) testing in bronchoalveolar lavage fluid (BALF, from "washing" a part of the lung and recovering the fluid for analysis), transtracheal wash fluid (from lavaging the trachea), lung biopsy, or postmortem tissue sampling.

Belgrave described several common observations in these cases, including fever, tachycardia (high heart rate), tachypnea (rapid, shallow breathing), increased abdominal work during exhalation, diminished lung sounds, cough, nasal discharge, bleeding from the nostrils, and poor body condition. Blood work showed chronic, systemic inflammation in several cases, and anemia (low red blood cell count) was seen in three horses.

Radiography (X rays) and ultrasonography provide the most striking evidence of the condition, showing characteristic nodules throughout areas of the lungs that appear as white lesions of various sizes on radiographs, often grouped together in masses.

Treatment included broad-spectrum antibiotics (all horses), corticosteroids (4/5), antiviral therapy with acyclovir or valacyclovir (3/5), and antifungal therapy (1/5). Two of the five horses survived; both received antiviral and corticosteroid therapy and had normal albumin/globulin ratios (comparative levels of certain proteins in the blood) at presentation, suggesting that the disease was caught early.

"Perhaps this ratio is a good prognostic indicator," Belgrave commented.

"Early diagnosis and treatment with antiviral therapy is critical for a successful outcome with equine multinodular pulmonary fibrosis," he concluded. "The duration of treatment should be determined by serial ultrasonographic and radiographic examinations as well as repeat polymerase chain reaction testing for EHV-5 on BALF."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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