🧬 Vet Infectious Disease Guide 2025: Hepatozoonosis in Dogs — Symptoms, Transmission & Supportive Care

Hepatozoonosis is a rare but often fatal tick-borne disease caused by the protozoa Hepatozoon canis or Hepatozoon americanum. Unlike most tick diseases, dogs don’t get sick from the bite—they become infected by eating the tick. I’m Dr Duncan Houston BVSc, and in this 2025 guide, I’ll help you understand this dangerous infection, how to recognize it, how it spreads, and what treatment options are available. 🐶

1. What Is Hepatozoonosis?

Hepatozoonosis is caused by a protozoan parasite—similar to amebas or other single-celled organisms. There are two main species that cause disease in dogs:

• Hepatozoon canis: Found worldwide, spread by brown dog tick (Rhipicephalus sanguineus)
• Hepatozoon americanum: More severe, found in the U.S., spread by Gulf Coast tick (Amblyomma maculatum)

Once the tick is ingested, the protozoa spread through the body and settle in the spleen, lymph nodes, or muscle tissue. This disease is not spread by tick bite—infection only happens if the dog eats the tick. 🐾🦠

2. How Do Dogs Get Infected?

• 🐶 Eating ticks: Often during grooming or hunting behavior
• 🦴 Eating rodents or birds that have ticks attached
• 👶 Puppies & immunocompromised dogs are at higher risk

Dogs cannot infect each other, and humans cannot catch hepatozoonosis from dogs.

3. Symptoms of Hepatozoonosis

3.1 Hepatozoon canis

Often mild or subclinical. When symptoms appear, they include:

• 🥱 Lethargy and weakness
• 🤒 Fever
• 🩸 Pale gums (anemia)
• 🧠 Enlarged lymph nodes or spleen

3.2 Hepatozoon americanum (more severe)

• 🔥 Muscle and joint pain
• 🐾 Lameness or reluctance to move
• 💥 Intense inflammation (immune overreaction)
• 🥵 High fever, weight loss, and wasting

Dogs with H. americanum often appear in extreme pain and may be unable to walk. If untreated, the disease is often fatal within 12 months. ⌛

4. Diagnosing Hepatozoonosis

Diagnosis involves multiple tools, especially when symptoms overlap with other illnesses. 🔬

4.1 Bloodwork

• 🧪 Elevated white blood cell count
• 💉 Anemia or low platelets
• 🧬 Inflammatory markers

4.2 Blood Smear Microscopy

In some cases, Hepatozoon organisms are visible in blood cells under the microscope.

4.3 X-rays or Imaging

Help identify inflammation, joint changes, or muscle damage (especially in H. americanum).

4.4 Muscle Biopsy

✅ Gold standard for H. americanum. Cysts in muscle tissue confirm the diagnosis.

5. Treatment & Management

5.1 No Cure, But Management Is Possible

There is no cure, but with appropriate treatment, many dogs can live longer and more comfortably. 🧡

5.2 Medications

• 💊 Antiprotozoal meds: Decoquinate, trimethoprim-sulfa, clindamycin, pyrimethamine
• 🧠 Anti-inflammatory meds: NSAIDs or corticosteroids (under vet guidance)
• 💉 Pain relief: Gabapentin, opioids, muscle relaxers

5.3 Supportive Care

• 🍽️ Nutritional support, high-calorie diets
• 🧴 IV fluids, syringe feeding if needed
• 🩸 Blood transfusion for severe anemia

💊 H. canis typically responds better to medication. H. americanum requires long-term supportive care. Chronic recurrence is common in both types. 🔄

6. Preventing Hepatozoonosis

Prevention is key, as treatment is difficult and relapses are likely. 🛡️

• 🐾 Use year-round tick preventives (chews, collars, topicals)
• 🌿 Treat yards to reduce tick habitats
• 🚫 Discourage hunting rodents, birds, or lizards
• 🧼 Check and remove ticks promptly to prevent ingestion

7. Ask A Vet: Early Help Matters

Suspect hepatozoonosis? Unexplained limping, fever, or muscle pain in a dog from a tick-endemic area? Use Ask A Vet for real-time help, symptom review, and test planning. 🩺

8. Summary Table

9. Final Thoughts

Hepatozoonosis is a reminder of how dangerous ticks can be—even without a bite. Though rare, this disease is devastating, and early detection matters. If your dog shows sudden signs of muscle pain, weakness, or fever and lives in a tick-heavy region, act quickly. Prevention is your best defense. 🛡️🐶

— Dr Duncan Houston BVSc

Need help with diagnosis, treatment planning, or prevention? Visit AskAVet.com or use the app to chat with a vet anytime. 💙