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Equine veterinary journal2025; 58(2); 458-465; doi: 10.1002/evj.70138

Equine leptospiral pulmonary haemorrhage syndrome: An atypical manifestation of equine leptospirosis.

Abstract: Leptospirosis is a widespread zoonotic, infectious disease associated with abortion, stillbirth, as well as liver and kidney failure. Leptospiral Pulmonary Haemorrhage Syndrome (LPHS) has increasingly been reported in human and canine patients infected by Leptospira and is associated with a high fatality rate. In equine medicine, pulmonary haemorrhage has mainly been described in foals with leptospiral infections, but rarely in adult horses. Objective: To characterise the clinicopathological features of pulmonary haemorrhage as a distinct disease entity in adult horses with leptospirosis, termed Equine Leptospiral Pulmonary Haemorrhage Syndrome. Methods: Retrospective case series. Methods: The clinical presentation, with blood biochemical, tracheobronchoscopic, ultrasonographic, and radiographic findings, as well as treatment and outcomes, is described in six adult horses. Leptospiral infection was confirmed by urinary PCR analysis and paired serology. Results: Cases had pulmonary haemorrhage accompanied by concurrent azotaemia. Thoracic radiographs revealed a structured interstitial pattern, with marked accentuation in the caudodorsal lung fields in all cases. Leptospiral infection was confirmed in 5/6 horses by urinary PCR analysis, and in all horses by early seroconversion. Four cases survived to hospital discharge. Conclusions: Small case series, incomplete clinical data, limited long-term follow-up. Conclusions: The term Equine Leptospiral Pulmonary Haemorrhage Syndrome is proposed to designate equine leptospirosis characterised by acute respiratory distress caused by pulmonary haemorrhage associated with blood biochemical disturbances including hyponatraemic and hypochloraemic azotaemia and increased serum amyloid A concentrations. The exact pathophysiology of pulmonary haemorrhage in equine leptospirosis remains incompletely elucidated. Urinary PCR analysis and paired serum microagglutination assays were useful to diagnose active leptospiral infection. The diagnostic benefit of tracheobronchial secretions remains an area for further investigation considering its potential source as a biohazard.
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Publication Date: 2025-12-26 PubMed ID: 41451997DOI: 10.1002/evj.70138Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This research article reports on an unusual form of leptospirosis in adult horses, characterized by severe lung bleeding, termed Equine Leptospiral Pulmonary Haemorrhage Syndrome (LPHS).
  • The study describes the clinical signs, diagnostic findings, treatment, and outcomes in six adult horses diagnosed with this condition, aiming to better understand this rare manifestation of equine leptospirosis.

Introduction to the Disease

  • Leptospirosis is a common infectious disease that affects both animals and humans, known for causing reproductive failure (abortion, stillbirth) and organ damage, particularly in the liver and kidneys.
  • Leptospiral Pulmonary Haemorrhage Syndrome (LPHS) has been reported more frequently in humans and dogs, where it causes bleeding in the lungs with a high risk of death.
  • In horses, pulmonary haemorrhage related to leptospirosis has mostly been seen in foals but is rare in adult horses.
  • This study aims to characterize LPHS as a distinct clinical syndrome in adult horses.

Study Design and Methods

  • The research is based on a retrospective case series, analyzing six adult horses presenting with pulmonary haemorrhage and confirmed leptospiral infection.
  • Clinical evaluation included:
    • Physical examination and clinical history
    • Blood biochemical testing to assess organ function and electrolyte levels
    • Tracheobronchoscopic examination to visualize the airways
    • Ultrasonography and thoracic radiographs to assess lung structure and abnormalities
    • Diagnostic confirmation using urinary PCR tests and paired serological microagglutination assays to detect Leptospira infection

Key Findings

  • All six horses presented with lung bleeding (pulmonary haemorrhage) along with signs of azotaemia—a condition indicating kidney dysfunction marked by elevated nitrogen waste products in the blood.
  • Chest X-rays consistently revealed a structured interstitial pattern, especially pronounced in the caudodorsal (rear and upper) lung fields in all cases.
  • Leptospiral infection was confirmed in five out of six cases by PCR analysis of urine samples, and all horses showed early seroconversion on paired serology, confirming active infection.
  • Four of the six horses survived to hospital discharge, indicating a somewhat favorable prognosis with proper treatment despite the severity.

Clinical and Laboratory Features

  • The syndrome is associated with acute respiratory distress caused by bleeding into the lung tissue.
  • Blood biochemical disturbances observed included:
    • Hyponatraemic azotaemia: Low sodium levels in the context of kidney dysfunction
    • Hypochloraemic azotaemia: Low chloride levels alongside kidney impairment
    • Elevated serum amyloid A concentration: Indicative of acute inflammation
  • Tracheobronchoscopic evaluation could detect haemorrhagic lesions, but the role and safety of sampling bronchial secretions remain uncertain due to potential biohazard risks.

Diagnostic Tools and Challenges

  • Urinary PCR analysis proved valuable for detecting active leptospiral infection in affected horses.
  • Paired serum microagglutination assays confirmed recent or ongoing infection through serological evidence.
  • The study highlights the need for further investigation into the diagnostic utility and biosafety of bronchial secretion samples in horses with this syndrome.

Conclusions and Implications

  • The authors propose the term Equine Leptospiral Pulmonary Haemorrhage Syndrome to define this distinct clinical manifestation of leptospirosis in adult horses.
  • This syndrome is characterized by acute respiratory distress due to lung bleeding combined with biochemical abnormalities indicative of kidney dysfunction and systemic inflammation.
  • The exact mechanisms causing pulmonary haemorrhage in these horses are not fully understood, highlighting an area for future research.
  • Although limited by small case numbers and incomplete long-term follow-up, the study provides important preliminary insights into diagnosis and clinical management of LPHS in adult horses.

Cite This Article

APA
Decoster C, Lefère L, Raes E, van Loon G, Dufourni A. (2025). Equine leptospiral pulmonary haemorrhage syndrome: An atypical manifestation of equine leptospirosis. Equine Vet J, 58(2), 458-465. https://doi.org/10.1002/evj.70138

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 58
Issue: 2
Pages: 458-465

Researcher Affiliations

Decoster, Céline
  • Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Ghent, University of Ghent, Merelbeke, Belgium.
Lefère, Laurence
  • Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Ghent, University of Ghent, Merelbeke, Belgium.
Raes, Els
  • Department of Morphology, Imaging, Orthopedics, Rehabilitation and Nutrition, Faculty of Ghent, University of Ghent, Merelbeke, Belgium.
van Loon, Gunther
  • Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Ghent, University of Ghent, Merelbeke, Belgium.
Dufourni, Alexander
  • Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Ghent, University of Ghent, Merelbeke, Belgium.

MeSH Terms

  • Animals
  • Horses
  • Horse Diseases / microbiology
  • Horse Diseases / pathology
  • Horse Diseases / diagnosis
  • Leptospirosis / veterinary
  • Leptospirosis / pathology
  • Leptospirosis / complications
  • Leptospirosis / microbiology
  • Leptospirosis / diagnosis
  • Hemorrhage / veterinary
  • Hemorrhage / pathology
  • Hemorrhage / microbiology
  • Lung Diseases / veterinary
  • Lung Diseases / pathology
  • Lung Diseases / microbiology
  • Female
  • Male
  • Retrospective Studies
  • Leptospira

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