What is the primary impact of the larvae of Strongylus vulgaris in equines?

The primary impact of the larvae of Strongylus vulgaris in equines is the inflammation of the cranial mesenteric artery. This condition arises because the larvae migrate through various tissues, including the walls of the arteries, during their life cycle. As they travel to the intestines, they can cause significant damage to the arterial walls, leading to inflammation. This inflammation can disrupt blood flow and lead to serious complications, including colic or even necrosis of the intestinal tissue.

While the other options present potential issues that affect equines, they are not associated with Strongylus vulgaris larvae. Severe muscle atrophy is typically related to other health issues rather than this specific parasite. Skin lesions and itching are more indicative of ectoparasites or other dermatological conditions. Respiratory distress is generally not a direct consequence of Strongylus vulgaris infection, as it primarily affects the gastrointestinal system rather than the respiratory tract. Therefore, the most relevant and damaging impact of Strongylus vulgaris larvae in horses is the inflammation of the cranial mesenteric artery.