Micropolyspora faeni causes airway inflammation but not hyperresponsiveness in sensitized ponies

Area of Science:

• Equine respiratory medicine
• Immunology
• Pulmonary physiology

Background:

• Recurrent airway obstruction (RAO) is a common respiratory disease in horses.
• Micropolyspora faeni is a known allergen implicated in RAO.
• Understanding the specific effects of M. faeni challenge is crucial for disease management.

Purpose of the Study:

• To evaluate the impact of aerosol Micropolyspora faeni challenge on pony respiratory function.
• To assess airway reactivity and bronchoalveolar lavage fluid cytology following M. faeni exposure.
• To differentiate responses between sensitized and control ponies.

Main Methods:

• Two groups of ponies: one sensitized to M. faeni, one control.
• Aerosol challenge with M. faeni antigen or saline.
• Measurements included lung function, airway reactivity to histamine, and bronchoalveolar lavage fluid cytology.
• Data collected at baseline and 5 hours post-challenge.

Main Results:

• M. faeni challenge increased respiratory frequency and minute ventilation in sensitized ponies.
• Arterial CO2 tension decreased in sensitized ponies post-challenge.
• Both groups showed increased neutrophils and decreased mononuclear cells in bronchoalveolar lavage fluid.
• No significant changes in pulmonary mechanics, gas exchange, or airway responsiveness were observed in control ponies or in overall airway responsiveness in sensitized ponies.

Conclusions:

• Aerosol M. faeni challenge induces pulmonary neutrophilia and ventilation abnormalities in sensitized ponies.
• The challenge did not result in increased airway hyperresponsiveness.
• These findings contribute to understanding the pathophysiology of M. faeni-induced respiratory disease in horses.