Hypertrophic osteopathy associated with mycotic pneumonia in two juvenile elk (Cervus elaphus)

Two yearling bull elk (cervus claphus) from the same farm developed anorexia, weight loss, and lameness. On physical examination, both elk were thin and showed diffuse swelling of all lower limbs. Radiographs of the lower limbs showed periosteal thickening of the distal extremities, consistent with hypertrophic osteopathy. Thoracic radiographs indicated the presence of pulmonary nodules. Cytologic evaluations of tracheal washes on both elk were consistent with inflammation. Acid-fast stains on both samples were negative. Because of the poor prognosis, both elk were euthanized. At necropsy, the carpal, metacarpal, tarsal, and metatarsal bones, as well as the radius, ulna, and tibia had thickening of cortical bone. There were multiple encapsulated nodules throughout the lungs, lymph nodes, and kidney, and smaller nodules in the myocardium. On microscopic examination, these nodules contained myriads of hyphae, and immunohistochemistry for Aspergillus sp. was strongly positive. Aspergillus fumigatus was isolated from affected tissue in 1 elk. Necropsy findings in both elk were consistent with disseminated fungal granulomas and periosteal hyperostosis. This case presents the first description of hypertrophic osteopathy in elk. The source of infection was undetermined, but inhalation of spores from contaminated feed or bedding was suspected.