Examination of the laryngeal musculature and recurrent laryngeal nerves of zebra (Equus burchelli) for evidence of idiopathic laryngeal hemiplegia

Abstract

Aims: This study was undertaken in order to determine whether wild Burchell's Zebra (Equus burchelli) are affected by Idiopathic Laryngeal Hemiplegia (ILH). ILH has a high prevalence in the domestic horse and a negative control population has not been identified.

dMethods:The work was conducted in two phases on two large farms in central Kenya during routine culls.The larynges of 42 zebra were removed and the left and right intrinsic laryngeal adductor and abductor muscles and recurrent laryngeal nerves were isolated. The muscles were weighed and biopsy samples of left and right recurrent laryngeal nerve and cricoarytenoideus lateralis muscles from 16 animals were taken for histological examination.

dResults: Left adductor muscles were observed to be significantly lighter than right adductor muscles (p = 0.001). There was no significant difference between the weights of left and right laryngeal abductors (p = 0.260). There was no light microscopic evidence of pathological changes consistent with ILH in any of the muscle or nerve samples.

dConclusions: Zebra do not appear to suffer from ILH and equids unaffected by ILH can have significantly lighter muscles on the left of the larynx.

dClinical relevance: Mild asymmetries of the larynx on palpation may not be a reliable indicator of ILH. Zebra may be a potentially useful negative control animal for observational ILH studies.

Key words::

• Laryngeal hemiplegia
• larynx
• muscle
• equid
• zebra