section name header

Basics ⬇

BASICS

Overview

  • EHV-5 is an equine gammaherpesvirus that establishes a lifelong latent infection in peripheral blood mononuclear cells, predominantly in equine B lymphocytes
  • EHV-5 is frequently detected in respiratory samples, ocular samples, and blood cells, sites of both primary infection and latency
  • Although EHV-5 has been detected in clinical samples from horses with no clinical disease, it has recently been associated with EMPF, a progressive nodular fibrotic lung disease. EHV-5 has been detected in bronchoalveolar lavage samples and postmortem tissue, and the highest loads of EHV-5 were detected in the most severe EMPF lesions
  • Whether the EHV-5 causes EMPF or the local pulmonary microenvironment associated with EMPF increases the EHV-5 load in the vicinity of the EMPF lesions is not yet clear
  • Systems affected—respiratory
  • EHV-5 has been commonly detected in clinical samples from clinically normal and diseased adult horses
  • EMPF should be considered in cases with presenting clinical signs of chronic weight loss, ill thrift, and/or tachypnea
  • EHV-5 has been detected in horse populations around the world

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Chronic, long-term, lower respiratory tract diseases such as interstitial or infectious pneumonia, pulmonary neoplastic disease, idiopathic pulmonary fibrosis.

CBC/Biochemistry/Urinalysis!!navigator!!

EMPF cases present with nonspecific clinicopathologic abnormalities, including anemia, leukocytosis, hyperfibrinogenemia, and/or hypoalbuminemia.

Other Laboratory Tests!!navigator!!

  • Histopathology on lung biopsy or postmortem samples have demonstrated marked pulmonary interstitial expansion by well-organized mature collagen with infiltration of mixed inflammatory cells and the preservation of “alveolar-like” architecture
  • There are a variety of molecular diagnostic tests available to detect EHV-5 in clinical samples

Imaging!!navigator!!

Thoracic ultrasonography to demonstrate generalized nodular consolidation and thoracic radiography to confirm the generalized distribution of the nodules and interstitial pattern.

Medications ⬆ ⬇

MEDICATIONS

Drug(s) of Choice

While supportive therapy is indicated, there is no evidence to support the use of any specific therapeutic regimen to treat EMPF, including administration of antiherpetic drugs such as valacyclovir (valaciclovir) or acyclovir (aciclovir).

Follow-up ⬆ ⬇

FOLLOW-UP

Expected Course and Prognosis

Some cases will recover, but generally the prognosis for cases of EMPF is guarded to poor.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Abbreviations!!navigator!!

  • EHV-5 = equine herpesvirus 5
  • EMPF = equine multinodular pulmonary fibrosis

Suggested Reading ⬆ ⬇

Hartley CA, Dynon KJ, Mekuria ZH, et al. Equine gammaherpesviruses: perfect parasites? Vet Microbiol 2013;167:86–92.

Williams KJ, Maes R, Del Piero F, et al. Equine multinodular pulmonary fibrosis: a newly recognized herpesvirus-associated fibrotic lung disease. Vet Pathol 2007;44:849–862.

Author(s) ⬆

Author: James R. Gilkerson

Consulting Editor: Ashley G. Boyle