Hepatozoonosis in Dogs: Causes, Symptoms and Care

Hepatozoonosis in dogs is a parasitic disease caused by protozoan organisms, primarily Hepatozoon canis and Hepatozoon americanum. Unlike many tick-borne diseases, dogs become infected by ingesting an infected tick rather than through a tick bite itself. The infection is most commonly seen in dogs that have travelled abroad, particularly to Mediterranean countries, though the responsible ticks exist in various parts of the world including the Middle East, Africa, Asia and the USA.

Causes and transmission

The disease is tick-associated, and the dog must swallow an infected tick to contract the parasite. Hepatozoon canis is found worldwide outside the USA, where Hepatozoon americanum predominates. These protozoan parasites enter the dog body following digestion of the tick and subsequently invade internal organs including the liver, spleen, lymph nodes and muscles.

Symptoms to watch for

Dogs infected with hepatozoonosis typically show early signs of illness that require prompt veterinary attention. The most common symptoms include:

• Lethargy and fatigue
• Fever
• Loss of appetite
• Weight loss
• Diarrhoea, often bloody

Dogs with weakened immune systems may experience more severe symptoms including:

• Pain and lameness
• Muscle wastage (muscle atrophy)
• Ocular discharge
• Pale gums and mucous membranes indicating anaemia
• Kidney failure
• Increased sensitivity to touch (hyperaesthesia)

Diagnosis

Vets rely on a thorough clinical examination combined with the dog travel history, particularly visits to tick-endemic regions. Diagnostic tests to confirm hepatozoonosis include a full blood count to detect anaemia or signs of infection, blood biochemistry to assess organ function, urinalysis, radiographs to check for bone involvement (particularly with H. americanum), and blood smears or PCR molecular testing to identify the parasite directly.

Treatment and management

Managing hepatozoonosis typically involves ongoing treatment. Vets administer specific antiparasitic injections every two weeks with the aim of reducing or eliminating the infection. Despite treatment, parasite DNA may remain detectable due to the difficulty of complete eradication, particularly with H. americanum. Treatment plans also focus on relieving symptoms such as pain and supporting affected organs. Regular veterinary follow-up is essential to monitor recovery.

Prognosis

If treatment begins early, dogs infected with H. canis generally have a good prognosis with successful symptom management. Infections caused by H. americanum tend to be more difficult to treat, and treatment rarely eradicates the parasite completely, with potential long-term complications.

Prevention: protecting your dog from tick-borne parasites

The best prevention against hepatozoonosis is effective tick control. Using high-quality antiparasitic products and promptly removing any ticks found on your dog are vital steps in reducing risk. Crucially, preventing dogs from grooming and accidentally swallowing ticks is important, as ingestion is the transmission route. Responsible ownership — including using vet-recommended antiparasitics and regular health checks — helps protect your dog health against this parasitic disease. Find puppies for sale on Pets4Homes from responsible breeders across the UK.