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  Discussion on Research Summary: EHV-5 and Chronic Pulmonary FIbrosis
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DrO

Posted on Thursday, Dec 6, 2007 - 7:14 am:

After reporting last month on the apparent innocuous behavior of EHV-2 we have a different story for EHV-5. Occasionally you see horses that have heave-like symptoms that are progressive and minimally responsive to COPD therapy. On investigation with radiography or ultrasound nodular lesions are found through the lungs and a metastatic disseminated cancer is suspected. Here is another cause of nodular lung disease in horses.
DrO


Vet Pathol. 2007 Nov;44(6):849-62.
Equine multinodular pulmonary fibrosis: a newly recognized herpesvirus-associated fibrotic lung disease.

Williams KJ, Maes R, Del Piero F, Lim A, Wise A, Bolin DC, Caswell J, Jackson C, Robinson NE, Derksen F, Scott MA, Uhal BD, Li X, Youssef SA, Bolin SR.

G380 Veterinary Medical Center, Michigan State University, East Lansing, MI 48824 (USA). williamsk@dcpah.msu.edu.

Pulmonary fibrosis and interstitial lung disease are poorly understood in horses; the causes of such conditions are rarely identified. Equine herpesvirus 5 (EHV-5) is a gamma-herpesvirus of horses that has not been associated with disease in horses. Pathologic and virologic findings from 24 horses with progressive nodular fibrotic lung disease associated with EHV-5 infection are described and compared with 23 age-matched control animals. Gross lesions consisted of multiple nodules of fibrosis throughout the lungs. Histologically, there was marked interstitial fibrosis, often with preservation of an "alveolar-like" architecture, lined by cuboidal epithelial cells. The airways contained primarily neutrophils and macrophages. Rare macrophages contained large eosinophilic intranuclear viral inclusion bodies; similar inclusion bodies were also found cytologically. The inclusions were identified as herpesviral-like particles by transmission electron microscopy in a single horse. In situ hybridization was used to detect EHV-5 nucleic acids within occasional macrophage nuclei. With polymerase chain reaction (PCR), the herpesviral DNA polymerase gene was detected in 19/24 (79.2%) of affected horses and 2/23 (8.7%) of the control horses. Virus genera-specific PCR was used to detect EHV-5 in all of the affected horses and none of the control horses. EHV-2 was detected in 8/24 (33.3%) of affected horses and 1/9 (11.1%) of the control horses. This disease has not been reported before, and the authors propose that based upon the characteristic gross and histologic findings, the disease be known as equine multinodular pulmonary fibrosis. Further, we propose that this newly described disease develops in association with infection by the equine gamma-herpesvirus, EHV-5.
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