Darker splenic tissue. A sixteen year old Lipizzaner stallion was seen by a referring veterinarian because the horse has had a 5 month history of recurrent nodular swelling of the preputial skin with episodes of ulceration and epithelial repair. The skin lesions have granulomatous inflammatory foci containing necrotic nematode larvae and are surrounded by eosinophils. The lesions are consistent those induced by migrating larvae of Habronema sp . Horses mount a strong T-cell and eosinophil immune and inflammatory response to the larvae as they migrate through subcutis following penetration of skin injuries and soft mucosal areas.
Ulceration can occur secondary to inflammatory-cell mediated damage.
With prolonged ulceration, skin lesions often develop granulation tissue as a reparative response.