Hepatozoon infections in domestic and wild Carnivora: etiology, prevalence, clinical disease, diagnosis and treatment, and redescription of Hepatozoon silvestris, H. martis, and H. ursi

Hepatozoon spp. are common pathogens in dogs and other Carnivora in many parts of the world, especially in the tropics. There is considerable taxonomic debate concerning the Hepatozoon species infecting Carnivora. Morphological descriptions of several Hepatozoon species are inadequate and their validity is questionable. Additionally, different terminology has been used for the description of life cycle stages. Here, we provide a comprehensive review of the Hepatozoon species in the Carnivora, using a uniform terminology. Worldwide prevalence of clinical and subclinical Hepatozoon infections for the past century is tabulated and critically evaluated. We also review the epizootiology, clinical signs, diagnosis, and treatment of hepatozoonosis in the Carnivora. The morphology and life cycles of seven valid species with known merogonic stages (Hepatozoon americanum, H. canis, H. felis, H. martis, H. rufi, H. silvestris, H. ursi) are summarized in a table using standard terminology. Additional information on H. apri, H. martis, and H. silvestris life cycle stages is provided. Information lacking for H. procyonis, H. luiperdjie and H. ingwe is discussed. The relevance of H. mustelis, H. banethi and H. ewingi is discussed and they are considered as invalid species. For the benefit of future researchers, worldwide reports of prevalence, clinical disease, diagnosis, and treatment of Hepatozoon infections in domestic and wild Carnivora for the past century are summarized in tables alphabetically and chronologically for each country. Co-infections of H. canis, H. americanum, H. felis, and H. silvestris are summarized and discussed. The role of Hepatozoon infections causing clinical illness in wild Carnivora is discussed, particularly for red foxes, coyotes, and mustelids.