Canine hepatozoonosis
Also called Hepatozoon canis infection
A parasite infection that dogs catch by swallowing a tick. It ranges from no signs to fever, weakness and anaemia, and is more serious in dogs with weakened immunity.
Cause and spread
- Cause
- The protozoan Hepatozoon canis (outside North America).
- How it spreads
- Dogs are infected by swallowing ticks (the brown dog tick, Rhipicephalus sanguineus) or animals that carry them, not by a tick bite.
Signs to watch for
- Often none
- Fever, lethargy and loss of appetite
- Anaemia
- Weakness and weight loss
Many diseases look alike. Only a laboratory test can tell them apart, so please see a veterinarian for any sick animal.
How it is diagnosed
The parasite can be seen inside white blood cells in a stained blood smear, or found by PCR. A blood count and biochemistry panel help assess the dog; anaemia is the commonest finding.
- Usually the first testBlood Smear ExaminationCan show the parasite inside white blood cells.
- Confirms the diseaseHepatozoon canis PCRDetects the parasite's genes.
- Supports the diagnosisComplete Blood Count (CBC)Shows anaemia.
- Supports the diagnosisCanine Haemoparasite PCR ProfileTests for Hepatozoon with Babesia.
Prevention and control
- Tick control and preventing dogs from eating ticks or tick-carrying prey
- Treat underlying diseases that weaken the immune system
Where this information comes from
- Old World Hepatozoonosis and American Canine Hepatozoonosis · Merck Veterinary Manual
General information for animal owners and veterinarians, last checked October 2026. It does not replace the advice of your veterinarian, who should decide which tests and treatment your animal needs.