The gametocytes undergo syngamy in the tick gut and produce a zygote. The zygote penetrates the gut wall and undergoes sporogony in the hemocoel, completing the life cycle. Clinically, Hepatozoon canis infections are associated with muscular pain and atrophy, lumbar pain, emaciation, lethargy, anemia, neutrophilic leukocytosis and periosteal new bone proliferation at sites of muscle attachment. Occasional lesions include pulmonary congestion, lymphadenopathy, gastric congestion, and pale kidneys. When mature schizonts rupture in muscle, there is an intense pyogranulomatous response characterized by about equal numbers of neutrophils and macrophages with varying numbers of eosinophils and few lymphocytes or plasma cells.
Bony proliferation is probably due to local muscle inflammation.
As demonstrated in this case, there is also vascular proliferation into the area of schizont rupture. Baneth G, Harmelin A, Presentey B. Hepatozoon canis infection in two dogs. Adult female Thoroughbred horse. The placenta was delivered with a live full term foal. The chorionic surface of the placenta was diffusely granular, thickened, and slightly pale.