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

Abstract

BACKGROUND: 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. OBJECTIVES: To characterise the clinicopathological features of pulmonary haemorrhage as a distinct disease entity in adult horses with leptospirosis, termed Equine Leptospiral Pulmonary Haemorrhage Syndrome. STUDY DESIGN: 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. MAIN LIMITATIONS: 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.