Histology and morphometry of Strongylus vulgaris-mediated equine mesenteric arteritis.

This study examined how the horse parasite Strongylus vulgaris, or the large bloodworm, affects the cranial mesenteric arteries in horses. It found that both the occurrence of blood clots and the severity of inflammation varied seasonally and were directly linked to the presence of the larvae. The research also revealed that changes to the inner and outer layers of the blood vessels were generally more severe than changes to the middle layer, and that these changes were largely due to the accumulation of collagen, which decreased the elasticity of the arteries.

Methodology and Samples

• For the study, histological (microscopic anatomy) and morphometric (measurement of forms) evaluations of equine cranial mesenteric arteries were performed.
• A total of 239 arteries underwent histological examination, while 89 were subjected to morphometric analysis.

Findings Related to Inflammatory Changes and Larvae Presence

• The histological examination revealed that the occurrence of thrombosis (blood clots) and the severity of inflammation in the arteries fluctuated depending on the season and were directly correlated with the presence of Strongylus vulgaris larvae.

Fibrosis in Different Arterial Layers

• The research also showed that fibrosis, or scarring, of the inner (intimal) and outer (adventitial) layers of the arteries was generally more severe than that of the middle (medial) layer.
• Fibrosis of the vasa vasorum (small vessels supplying the walls of blood vessels) was found to be less common than fibrosis of the artery itself.

Morphometric Analysis and Its Results

• The morphometric analysis demonstrated a significant increase in the area of the intimal, adventitial, and to a lesser extent, medial layers in arteries affected by Strongylus vulgaris as compared to healthy arteries.
• This increase in area was due to the accumulation of collagen, a structural protein found in connective tissues. This led to decreased arterial elasticity, affecting the arteries’ ability to stretch and accommodate blood flow.
• The study also noted that the area inside the arteries (luminal area) varied greatly among the affected arteries, suggesting heterogeneity in the ways different arteries respond to the parasite.