Polypoid nasal neoformations in sheep: Pathological investigations

This paper reports four cases of nasal polyps in adult sheep from Piedmont and Sicily farms. The clinical course and post-mortem findings are described. Macroscopically numerous nasal polyps obstructing the nasal cavities, with the erosion of nasal concha, were observed. Histologically the neoformations, consisting of a different number of fusiform fibrocytic cells arranged in a variable amount of amorphous mesenchymal matrix, were located in the submucosa and covered by a simple disorganized columnar epithelium. Non-suppurative infiltration was also observed. Microbiological investigations revealed positivity for Pseudomonas aeruginosa only in one case; no bacteria were isolated in polyps collected from the other three sheep. Chronic and massive infestation by Oestrus ovis was present in three cases. The etiology and pathogenesis of these proliferations remain to be clarified, even if the authors postulate that one biological agent (bacterium or parasite) may have been responsible for the reaction of the nasal mesenchyma.