Pulmonary fibrosis in horses associated with spontaneous Crotalaria juncea intoxication.

Pulmonary fibrosis and respiratory distress in horses were linked to spontaneous intoxication by the plant Crotalaria juncea in northeastern Brazil, resulting in severe lung and liver damage.

Background and Objective

• Researchers observed an outbreak of illness in horses featuring progressive weight loss and breathing difficulties.
• The study aimed to investigate the cause of these symptoms and associated pathological findings.
• The location of the outbreak was in the northeastern region of Brazil.

Clinical Presentation in Horses

• The affected horses exhibited signs of progressive weight loss, indicating a chronic disease process.
• Respiratory distress was a prominent symptom, suggesting compromised lung function.

Pathological Findings from Necropsies

• Lung Observations:
  • Lungs were described as firm and non-collapsed, an abnormal finding indicating lung tissue stiffness.
  • Extensive interstitial fibrosis was present, meaning widespread scarring within lung tissue.
  • Bronchiolar epithelial hyperplasia was observed, which is an abnormal increase in the number of cells lining the small airways.
  • Proliferation of club cells, specialized airway cells involved in repair and defense, was seen indicating a response to injury.
  • Marked pulmonary arterial remodeling was detected, which involves changes in the blood vessel structure likely contributing to respiratory problems.
• Liver Observations:
  • Primarily centrilobular necrosis was noted, indicating liver cell death around the central vein area of liver lobules.
  • This was likely due to hypoxic injury caused by anemia and potentially prolonged agonal (dying) phases before death.

Exposure and Environmental Factors

• Inspection of the horses’ pasture identified significant invasion by the plant Crotalaria juncea.
• Plants were observed in multiple phenological stages, meaning different growth phases were present simultaneously.
• Crotalaria juncea is known for containing pyrrolizidine alkaloids which are toxic, especially to the liver.
• Spontaneous intoxication with this plant was considered the cause of the pulmonary fibrosis and other symptoms in horses.

Summary and Implications

• The study linked spontaneous ingestion or exposure to C. juncea with severe lung fibrosis and liver damage in horses.
• This intoxication manifested with progressive respiratory signs and weight loss due to combined lung and liver effects.
• Recognition of such outbreaks and identification of toxic plants in pastures is crucial for preventing morbidity and mortality in horses.
• The findings highlight the importance of pasture management in endemic areas to control exposure to toxic plants like Crotalaria juncea.