Lymphocytic neuritis of the ileum in sheep with naturally acquired and experimental paratuberculosis.

In a comparison of natural and experimentally induced ovine paratuberculosis, aggregations of mononuclear inflammatory cells were detected around nerves in the ileal submucosa in eight of 12 sheep with natural disease and in five of 14 animals with unequivocal experimental paratuberculosis. Such lesions were not seen in 10 other sheep that, despite attempted experimental infection, remained free from the disease, as judged clinically, histopathologically and by PCR assay. The lesions described resembled those observed in human leprosy.