Multinodular pulmonary fibrosis in horses: 46 cases (2009-2019)

I have encountered a few of these horses in practice. As found in this study, EHV-5 is associated with the disease and is thought to be the cause. The patients present very much like a horse with equine asthma (Heaves, COPD, or RAO) but are poorly responsive to steroids with a progressive worsening despite environmental changes that should improve a horse with asthma. Radiology or ultrasound can visualize the nodules and a biopsy can confirm the diagnosis. The prognosis is poor for long-term survival.
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Clinical findings and outcome predictors for multinodular pulmonary fibrosis in horses: 46 cases (2009-2019)
J Vet Intern Med. 2024 Apr 15. doi: 10.1111/jvim.17084. Online ahead of print.
Authors
Amanda Craven 1 , Amy Todd-Donato 1 , Tracy Stokol 2 , Rachel Liepman 3 , Ilana Glasberg 4 , Pamela Wilkins 4 , Daniela Luethy 5 , David Wong 6 , Angelika Schoster 7 , Astrid J van den Brom-Spierenburg 8 , Joy E Tomlinson 5 9
Affiliations

1 Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
2 Department of Population Medicine and Diagnostic Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.
3 Cave Creek Equine, Phoenix, Arizona, USA.
4 Department of Veterinary Clinical Medicine, University of Illinois College of Veterinary Medicine, Urbana, Illinois, USA.
5 Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
6 Department of Veterinary Clinical Sciences, Iowa State University College of Veterinary Medicine, Ames, Iowa, USA.
7 Vetsuisse Faculty, Equine Department, University of Zurich, Zurich, Switzerland.
8 Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
9 Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, New York, USA.

PMID: 38619130
DOI: 10.1111/jvim.17084

Abstract

Background: Prognostic indicators for equine multinodular pulmonary fibrosis (EMPF), an interstitial fibrosing lung disease, are poorly described.

Hypothesis/objectives: Describe diagnostic findings and outcome predictors for EMPF.

Animals: Forty-six adult horses with EMPF.

Methods: Retrospective multicenter case series from 2009 to 2019. Radiographic (n = 27) and ultrasonographic studies (n = 19) from EMPF horses and bronchoalveolar lavage fluid (BALF) cytology from 6 EMPF and 13 asthma cases were independently reviewed and blinded to diagnosis and outcome. Associations between predictor variables and survival were assessed by predictor screening followed by Fisher’s exact and Wilcoxon rank sum tests.

Results: Primary clinical findings were weight loss (36/46, 78%), increased respiratory effort (33/46, 72%), tachypnea (32/46, 70%), and fever (18/46, 39%). Macrophage atypia was seen in more EMPF than asthmatic horse BALF (67% vs. 8%; P = .02). Equine herpesvirus 5 (EHV-5) was detected in 24 of 30 (80%) and hyperfibrinogenemia in 25 of 28 (89%) cases. Twenty-seven of 46 horses (59%) and 11 of 45 (24%) survived to discharge and to 3 months, respectively. Three-month survival was associated with lower median (range) respiratory rates (30 [24-36] vs. 41 [30-60] breaths per minute; P = .04), and higher BALF lymphocyte:neutrophil ratios (4.7 [1.4-22] vs. 0.47 [0.11-1.9]; P = .01) and blood lymphocyte counts (1.25 [0.93-2.55] vs. 0.90 [0.70-1.24] × 109/L; P = .03). Imaging findings, EHV-5 detection, and corticosteroid treatment were not associated with survival.

Conclusions and clinical importance: Fever is not a sensitive clinical sign of EMPF. Diagnostic testing should be pursued for horses with increased respiratory rate and effort and weight loss. The prognosis for EMPF horses is poor. Corticosteroid treatment does not improve 3-month survival.

Keywords: asthma; bronchoalveolar lavage; equine herpesvirus‐5 (EHV‐5); tracheal wash.

© 2024 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.