Insect Bite Hypersensitivity in Horses is Associated with Airway Hyperreactivity.

Area of Science:

• Veterinary Medicine
• Equine Health
• Immunology

Background:

• Genetic and epidemiologic data suggest co-occurring hypersensitivity manifestations in horses.
• Insect bite hypersensitivity (IBH) is a common allergic skin condition in horses.

Purpose of the Study:

• To investigate airway hyperreactivity (AH) and blood oxygen levels in horses with IBH, with or without equine asthma (EA).
• To determine if IBH is associated with subclinical respiratory changes.

Main Methods:

• Compared healthy horses (C), horses with IBH alone (IBH), and horses with both IBH and EA (IBH/EA).
• Assessed clinical history using standardized questionnaires (HOARSI, IBH scoring).
• Measured arterial partial pressure of oxygen (PaO2) and used flowmetric plethysmography for histamine airway challenge tests.

Main Results:

• Horses with IBH (alone or with EA) showed significantly lower histamine provocation concentrations (PC35, PC50, PC75) compared to healthy controls, indicating AH.
• Horses with IBH (alone or with EA) had significantly lower PaO2 levels than healthy controls.
• These respiratory changes were present even in horses without overt clinical signs of EA.

Conclusions:

• Insect bite hypersensitivity is associated with airway hyperreactivity and decreased blood oxygen levels in horses.
• These findings highlight a potential link between skin allergies and subclinical respiratory dysfunction in horses.
• IBH may contribute to or exacerbate respiratory issues in horses, even in the absence of apparent asthma symptoms.