- Fibrinous necrotising diphtheritic inflammatory process
- Most often caused by Aspergillus spp.
- Tends to invade neighbouring structures - nerves (causing e.g. laryngeal hemiplegia), blood vessels (rupture of internal carotid), bones (osteitis, fusion of stylohyoid and petrous temporal bones)
- Often associated with haemorrhage (see epistaxis)
2. Guttural Pouch Mycosis:
- Fungal infections (Aspergillosis).
- Typically affect caudodorsal medial compartment.
- Signs: painful swelling in parotid region, abnormal carriage of head and neck, nasal discharge, and the horse may be head shy.
- Erosion of the roof of the guttural pouch produces a variety of signs by damage to important structures directly related to the pouch:
a) Epistaxis: nasal bleeding. Erosion of internal carotid artery severe, maybe even cause fatal haemorrhage.
b) Dysphagia: difficulty in swallowing. Paresis of the pharynx and soft palate is caused by lesions involving the glossopharyngeal and vagus nerves.
c) Laryngeal Hemiplegia: roaring - following vagus involvement.
d) Horner's Syndrome: nasal congestion, drooping of upper eyelid, miosis, sweating and hyperaemia on same side of face. From involvement of sympathetic nerve (cranial cervical ganglion).
e) Facial Paresis: rare.
f) Tongue Paralysis: rare.
g) Vestibular Signs and Arthritis: alanto-occipital joint - very rarely.