Equine Multinodular Pulmonary Fibrosis in association with an EHV-5 infection in 5 horses

Between 2006 and 2008, 5 adult horses hailing from South Germany (4/5 cases) and Austria (1/5) with different case histories but similar lung lesions were investigated at the Faculty of Veterinary Medicine of the Ludwig-Maximilians-University in Munich. Anamnesis included amongst others ongoing respiratory symptoms, weight loss, and poor body condition. Pathological examination of the lungs revealed a severe chronic interstitial and fibrosing pneumonia with acute inflammatory components, which differs significantly from other fibrosing lung diseases due to its nodular pattern, the remodelling of the lung architecture, and the presence of eosinophilic intranuclear viral inclusion bodies within intraluminal macrophages. Neither bacteria nor fungi could be detected using special staining methods. In 4 horses, PCR analysis of paraffin-embedded lung tissue was initiated and yielded positive results for equine herpesvirus type 5 (EHV-5) DNA in all cases. Additionally, EHV-2 DNA was detected in 3 horses. Based on histopathological findings and PCR results, the diagnosis of equine multinodular pulmonary fibrosis (EMPF) associated with an infection of EHV-5 was established. EMPF was first recognised in 2005 in the USA. To the best of our knowledge, this is the first report on the occurrence of EMPF in Europe. Schlüsselwörter: Pferd, Lunge, Equine Multinoduläre Pulmonale Fibrose, EMPF, Equines Herpesvirus, EHV-5, EHV-2.