Canine hepatozoonosis: Pathophysiology, diagnosis, and treatment

Canine hepatozoonosis is caused by the protozoal organism Hepatozoon canis. Dogs become infected after ingestion of ticks that harbor mature oocysts. The disease has been diagnosed in many countries. The syndrome associated with this organism in the United States is different from that found elsewhere in the world. Dogs with American hepatozoonosis demonstrate signs of fever, muscle pain, and cachexia and often have moderate to extreme leukocytosis. A unique stage of the organism is found in the skeletal muscle of infected dogs from the United States. In other regions of the world, infection with H. canis is frequently subclinical. In dogs that are immunosuppressed or very young, severe and life-threatening disease may occur. Glomerulonephritis, amyloidosis, and the nephrotic syndrome are common sequelae of the disease. Diagnosis usually requires muscle biopsy because of the infrequency with which gametocytes are evident in the blood. In addition to being diagnosed in dogs, hepatozoonosis has been diagnosed in domesticated cats as well as many wildlife species. Recent reports indicate that the disease in the United States is no longer limited to the Texas Gulf Coast region but has also been seen with increasing frequency in the southeastern region.