Lameness in sheep may be caused by a number of systemic diseases, some of which include navel/joint ill (Escherichia coli and Erysipelothrix), tetanus, white muscle disease, frostbite, chlamydial polyarthritis, rickets, enzootic ataxia (copper deficiency), mastitis, orchitis, nutritional osteodystrophies, selenium toxicosis, laminitis, dermatophilosis, bluetongue, ulcerative dermatosis, and in some countries, foot-and-mouth disease. Weakness, ataxia, and neurologic problems may be misinterpreted as lameness in diseases such as scrapie, listeriosis, and visna. Additional information on differential diagnosis, treatment, and prevention can be found under the specific topics (see Musculoskeletal System Introduction and {blank} Nervous System Introduction).