Morphological findings in the cranial mesenteric artery of horses with verminous arteritis

Abstract

Cranial mesenteric arteries of 18 sacrificed necropsied horses of both sexes and different age groups were described in this paper. After macroscopic examination tissue samples for pathohistological examinations were routinely processed and stained with hematoxylin eosine (HE), Weigert van Gieson and Periodic-Acid-Schiff (PAS) staining. Immunohistochemical staining was performed on selected sections using avidin-biotin-peroxidase complex technique for ásmooth muscle actin (α-SMA). Enlarged, thickened cranial mesenteric arteries with a hardelastic consistency and narrowed lumen, were macroscopically evident in all examined sick horses. Live larvae of Strongylus vulgaris, situated free in the lumen, or attached to the intima of the blood vessel or incorporated in the thrombus were noted macroscopically in 37.5% examined sick horses. Inflammatory and fibrous changes were noticed and were present in the intima, media and adventitia of the blood vessel. The inflammatory infiltrate in the intima of the cranial mesenteric artery consisted of eosinophils, macrophages, plasma cells, lymphocytes and rare multinucleated giant cells and was situated mostly close to the Strongylus vulgaris larvae. Beside inflammatory changes, intimal fibrosis and extension, characterized by increased proliferation of α-SMA positive cells, was notable. Lesions of the internal elastic lamina consequently led to an inflammatory and fibrotic reaction in the tunica media. Fibrosis of the media characterized by the presence of connective tissue cells and fibers, as well as smoothmuscle cells, was present in 93.75% examined sick horses. Inflammation and fibrosis were mildest in the adventitia. Lesions of vasa vasorum were present in 81.25% examined sick animals were characterized by fibrosis, obliteration, perivascular cellular infiltration, mostly with eosinophils and findings of intimal bodies. All described changes are characteristic for cranial mesenteric artery verminous arteritis