Pathological fracture induced by Halicephalobus gingivalis (Nematoda: Rhabditida) in a horse limb.

Halicephalobus gingivalis is a free-living nematode that occasionally causes infections in horses. We report a rare case of limb fracture of horse caused by infection with H. gingivalis. An 8-year-old mare was referred to the Veterinary Hospital of the Federal University of Lavras with claudication grade 5 of the right hind limb, that had been started 3 months ago. The patient had aseptic arthritis in the tarsal joint and edema that extended to the quartile. The radiographic examination showed punctate osteolysis with exacerbation of bone trabeculation along the calcaneus, talus, proximal epiphysis of the third metatarsal and distal epiphysis of the tibia. Treatment for arthritis was initiated, and the animal showed a slight improvement in limb function. However, 21 days after hospitalization, due to a comminuted fracture of the tibia, it was euthanized. At necropsy, yellowish masses were found from the metatarsal to the tibia, and around the tarsal bones and joint. Similar masses were also found in the left kidney. Numerous nematodes compatible with H. gingivalis were identified. This is the first description of a pathological fracture caused by H. gingivalis infection in an equine limb.