Arteritis

Endarteritis. Courtesy of A. Jefferies

Presence of inflammatory cells within and around the vessel wall. Vasculitis often increases vessel permeability, presenting as oedema and haemorrhage. Petichial and ecchymotic haemorrhages within mucosae are characteristic.

Multiple aetiologies:

Infective

• Bacterial: Often toxin damage E.g. Salmonellosis, Erysipelas.
• Viral: Epitheliotropic viruses E.g. Equine arteritis, Canine distemper.
• Mycotic: Mucormycosis.

Parasitic

Verminous arteritis. Courtesy of A. Jefferies

The main parasitic lesion of the arteries in th UK is Strongylus vulgaris of horses. Larvae and mmatures migrate along arterial walls, particularly cranial mesenteric and ilio-caecal arteries with occasional aberrent migration to the ascending aorta.

Non-infective

Polyarteritis nodosa

Fibrinoid necrosis of the media of arteries and arterioles. An intense neutrophil infiltration may be identified which, when the lesions become chronic, is accompanied by cells such as eosinophils, plasma cells and lymphocytes.

Aetiology unknown but thought to be an antibody-antigen reaction.

Fibrinoid degeneration. Courtesy of A. Jefferies

Fibrinoid necrosis is also a feature of vessel damage. Seen with uraemia in dogs where the ammonia within the bloodstream irritates the endothelial layer. The affected arteries include the gastric arteries which, when damaged, result in ischaemia and gastric ulceration.