CHARACTERIZATION OF LESIONS INDUCED BY SPIROCERCA VULPIS (SPIRURIDAE: SPIROCERCIDAE) IN RED FOXES (VULPES VULPES).

Spirocerca lupi infection in dogs (Canis domesticus) is associated with esophageal lesions that may evolve to a neoplastic stage in the form of esophageal sarcoma. In the red fox (Vulpes vulpes) infected with the closely related Spirocerca vulpis, similar lesions may occur in the stomach, but neoplastic forms have not been reported. We characterize Spirocerca vulpis-induced lesions in the fox, using pathology and immunohistochemical (IHC) techniques. Seventy-one out of 163 Spirocerca vulpis-positive red foxes were selected and subjected to histopathological study. Lesions were classified as patchy or diffuse. Ten patchy and 10 diffuse lesion samples were studied using three IHC markers (CD68, CD3, and CD79α for macrophages, T lymphocytes, and B lymphocytes, respectively) and H&E stain for neutrophils and eosinophils. Intensity of necrosis, hemorrhages, and the presence of collagen was also analyzed. Of the S. vulpis-positive red foxes, 96.9% had S. vulpis nodules localized in the gastric area (wall and/or omentum), and 3.1% had nodules in the small intestine. All the samples had a moderate to severe lymphoplasmacytic infiltrate. Mild eosinophil infiltration was observed in both types of lesions, while neutrophil infiltration was significatively higher in the patchy than in the diffuse lesions. Fibrosis with mature collagen fibers was also predominant in the patchy lesions along with the presence of T lymphocytes and macrophages. Both the patchy and diffuse patterns had very few B lymphocytes. These findings suggest that the diffuse form is an earlier stage of the lesion, which eventually evolves into patchy forms. Neoplastic forms were not seen. Although more studies are necessary, this study describes the lesions, characterizes the inflammatory infiltrates, and establishes a possible evolution of the different pathological forms of S. vulpis infection in the red fox.