Canine hepatozoonosis is caused by species of the parasite Hepatozoon spp., which parasitize leukocytes of the host animal. Unlike most other tick-borne diseases, Hepatozoon spp. are transmitted to new animals by ingestion of an infected tick.
Canine hepatozoonosis is no zoonosis. Cats can be infected with Hepatozoon spp., but there is no clear understanding to date of the species involved.