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Hepatozoonosis in Dogs

What is Hepatozoonosis?

Hepatozoonosis in dogs is an infectious illness triggered by a protozoan parasite. There are two primary variants: Hepatozoon canis, transmitted by the Brown Dog tick, and Hepatozoon americanum, transmitted by Gulf Coast ticks.

Dogs typically contract the disease by ingesting a tick carrying the parasite or by consuming prey animals infected by ticks. Dogs with outdoor access, particularly those who hunt or scavenge, are at greater risk, especially in regions with high populations of Brown Dog or Gulf Coast ticks. Symptoms usually manifest 4 to 10 weeks after tick ingestion.

Hepatozoonosis is prevalent in the southeastern and south-central United States, notably in states like Texas, Louisiana, Alabama, Georgia, Mississippi, Oklahoma, Tennessee, and Florida, where Brown Dog and Gulf Coast ticks are abundant.

Untreated Hepatozoonosis caused by H. Americanum can lead to severe debilitation and eventual fatality within a few months. It’s important to note that humans are not susceptible to this disease, as it cannot be transmitted from dogs to humans.


Symptoms of Hepatozoonosis in dogs vary depending on the specific parasite causing the infection. Infections with H. canis typically exhibit milder symptoms, as these organisms tend to reside within the immune system (such as lymph nodes and bone marrow) and blood storage organs (like the spleen). Common symptoms include enlarged lymph nodes, pale gums, and lethargy, with some infected pets displaying very mild or even undetectable symptoms.

On the other hand, infections with H. americanum can lead to more severe symptoms without proper treatment. These symptoms may include fever, lethargy, weight loss, muscle or bone pain, muscle loss, and discharge from the eyes. Pet owners may initially observe reluctance to rise, a stiff gait while walking, and lethargy due to fever. Dogs may also become hypersensitive to touch (hyperesthesia) and exhibit scratching or self-mutilation behaviors. As the condition progresses, muscle loss may become apparent.


The transmission of Hepatozoonosis in dogs differs from typical tick-borne diseases, as it occurs through the ingestion of an infected tick rather than through a tick bite. Dogs may also contract the infection by consuming the carcass of a wild animal contaminated with ticks. Recent research indicates that dogs can acquire the infection from consuming an infected wild animal, even without directly ingesting a tick. Fortunately, Hepatozoonosis cannot be transmitted from one dog to another.


Diagnosing hepatozoonosis in dogs begins with a thorough examination of the dog’s daily activities, location, and recent exposure to ticks. Additional diagnostic methods may include:

  • Conducting a physical examination
  • Performing a complete blood count
  • Analyzing blood chemistry
  • Conducting a urinalysis
  • Utilizing X-rays
  • Conducting PCR testing
  • Considering muscle biopsy

During the diagnostic process, veterinarians will specifically look for signs of anemia, elevated levels of neutrophils in the blood, and, rarely, the presence of the protozoan in the blood sample. X-rays are employed to detect bone lesions. These diagnostic tests help rule out other conditions with similar symptoms, such as diskospondylitis, meningitis, canine distemper, polyarthritis, and other tick-borne diseases in dogs.

Following these initial assessments, veterinarians often send out a PCR test to confirm the presence of the infection. This test detects the protozoan’s DNA in the dog’s bloodstream. In some cases, a muscle tissue biopsy may be required to definitively confirm the presence of the protozoan, as muscles are a primary location for the organism to inhabit.


Although hepatozoonosis in dogs cannot be completely cured, treatments are available to manage symptoms and prolong survival. Treatment approaches include hydration, assisted feeding with a high-calorie diet, and the administration of non-steroidal anti-inflammatory drugs to reduce inflammation and alleviate pain.

To combat the protozoan infection, veterinarians typically prescribe anti-protozoal medications, which can extend the dog’s lifespan and improve their quality of life. Two commonly used therapy options include:

  • TCP therapy, consisting of three medications:
    • Trimethoprim-sulfadiazine (an antibiotic)
    • Clindamycin (also an antibiotic)
    • Pyrimethamine (an anti-parasitic)
  • Another option involves the use of ponazuril, an anti-parasitic medication that may be administered alone.

Additionally, veterinarians may recommend long-term treatment with decoquinate, an anti-parasitic medication that can be mixed with food and given twice daily for a duration of 2 years. This treatment aims to reduce the likelihood of symptom recurrence. While this therapy doesn’t completely eradicate the protozoa from the dog’s system, it diminishes their numbers, thereby reducing inflammation and associated symptoms. However, relapse of symptoms is common, typically occurring within 2-6 months after discontinuing decoquinate. Without treatment, the disease can lead to debilitation and muscle wasting, potentially resulting in death within months.

For H. canis infections, treatment typically involves the use of an anti-protozoal medication called imidocarb, administered twice monthly for several months. With consistent care, healthy dogs without additional diseases may potentially be cleared of the protozoan infection.

Living and Management

The triple combination therapy is typically recommended for a duration of 14 days. Within this timeframe, if the dog responds positively to the treatment, improvements in movement and activity should be observed as pain diminishes. Decoquinate therapy has been utilized in dogs with hepatozoonosis for an extended period, with the general agreement being that it extends survival time and maintains a good quality of life. It’s crucial to note that hepatozoonosis cannot be cured in dogs, and managing the disease is an ongoing commitment throughout their lifetime.


The primary method for preventing Hepatozoonosis in dogs is to prevent them from ingesting ticks. There are numerous safe and efficient tick treatments available, which can be administered every 1-3 months. Additional preventive strategies include:

  • Implementing year-round tick control for your dog, especially in areas where the disease is prevalent.
  • Preventing your dog from consuming prey animals outdoors, particularly in regions where ticks are abundant.
  • Maintaining a tick-free environment in your home and yard, which may necessitate professional pest control assistance.

Hepatozoonosis in Dogs FAQs

Can canine hepatozoonosis be transmitted to humans?

No, canine hepatozoonosis cannot be transmitted to humans.

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