Changes in nasal mucosal innervation in horses with grass sickness

Area of Science:

• Veterinary Neurology
• Equine Medicine
• Autonomic Nervous System Research

Background:

• Equine grass sickness (EGS) is a fatal dysautonomia causing autonomic nerve damage.
• Rhinitis sicca (dry nose) is a common clinical sign in chronic EGS cases.
• Alterations in nasal mucosal autonomic innervation are hypothesized to cause rhinitis sicca.

Purpose of the Study:

• To assess nerve fiber expression and distribution in the nasal mucosa of horses with and without EGS.
• To compare innervation density using markers like CGRP, SP, PGP 9.5, and PAN-N.

Main Methods:

• Immunohistochemistry was used to analyze nasal mucosal biopsies.
• Innervation density and distribution were quantified in normal horses and EGS cases (acute, subacute, chronic).

Main Results:

• PGP 9.5 showed superior staining for general neuronal markers compared to PAN-N.
• A significant reduction in sensory neuropeptide (SP and CGRP) innervation was observed in chronic EGS.
• SP innervation density was significantly lower in chronic EGS compared to normal and acute cases.

Conclusions:

• Equine dysautonomia leads to reduced sensory neuropeptide expression in nasal mucosa.
• This denervation likely underlies the rhinitis sicca observed in EGS.
• Nasal biopsy may be valuable for diagnosing EGS and managing its associated rhinitis.