Hepatozoonosis is a tick-borne disease caused by the protozoan Hepatozoon. It can be triggered by two species: Hepatozoon canisand H. americanum. H. canis is widespread, found in Asia, Africa, the Caribbean, Europe, and South America. In contrast, H. americanum is mainly seen in the southern and southeastern United States.



Transmission

H. canis is transmitted by the brown dog tick, Rhipicephalus sanguineus. In North America, H. americanum is transmitted by the Gulf Coast tick, Amblyomma maculatum, rather than by the brown dog tick. Dogs become infected by ingesting ticks carrying the organism. Once inside, the parasite is released from the tick, penetrates the dog's intestinal wall, and spreads to various organs, including the spleen, liver, lymph nodes, bone marrow, lungs, and pancreas.



Clinical signs

Infections caused by H. canis are generally milder. These pathogens tend to inhabit the immune system's regions, such as the lymph nodes and bone marrow, as well as blood storage organs like the spleen. Symptoms often include swollen lymph nodes, pale gums, and general fatigue. Some pets with H. canis may exhibit mild or no symptoms at all.

In contrast, H. americanum infections can lead to more severe health issues if left untreated. Affected pets may show a range of symptoms, including elevated body temperature, fatigue, loss of appetite, weight loss, muscle or bone pain, muscle mass deterioration, and eye discharge.

Pet owners might first notice their dog hesitating to stand, walking stiffly, and appearing fatigued, often indicative of a fever. The dog might become more sensitive to touch, leading to scratching or self-injury. As the infection advances, significant muscle loss may become evident.



Diagnosis

Hepatozoonosis can lead to several changes in baseline laboratory tests. A complete blood cell count may reveal anemia and leukocytosis (high white blood cell count). Your dog might also show elevated liver enzyme levels, decreased blood protein levels, and increased enzymes associated with muscle inflammation. H. americanum can also cause bony changes, visible on X-rays, and may be identified through muscle biopsy.

Microscopic examination of an infected dog's blood can detect H. canis within white blood cells. Additionally, PCR testing is used to identify the infection and differentiate between H. americanumand H. canis.



Treatment

The approach to treating hepatozoonosis varies based on the infecting species.

For H. americanum infections, a complete cure is not possible, but many dogs can achieve long-term remission with proper treatment. The typical regimen involves three medications—trimethoprim-sulfa, clindamycin, and pyrimethamine—administered until the dog is symptom-free. Once symptoms subside, a maintenance medication, decoquinate, is prescribed for at least two years. The treatment duration may be extended based on the dog's symptoms and lab test results. If symptoms reappear after treatment, the medication regimen may need to be reinstated.

In cases of H. canis infection, treatment is simpler, typically involving the anti-protozoal drug imidocarb, administered twice monthly for several months. This may be supplemented with oral doxycycline to enhance effectiveness. This treatment strategy usually leads to symptom resolution, allowing dogs to maintain a high quality of life with minimal risk of relapse.

In addition to species-specific treatments, supportive care is crucial for all dogs with hepatozoonosis. This may include anti-inflammatory drugs to alleviate pain or reduce fever and intravenous fluids for dogs with appetite or hydration issues. Treatment for any concurrent tick-borne diseases may also be necessary. Importantly, starting an effective tick prevention regimen is essential to prevent reinfection with hepatozoonosis.



Control and prevention

To safeguard dogs against hepatozoonosis, the primary strategy is to minimize their exposure to ticks. Using a tick-prevention product recommended by a veterinarian is essential. Additionally, since hepatozoonosis can be spread by consuming infected prey, restricting dogs' opportunities to hunt or scavenge will further reduce the risk of infection.



Note

Bioguard’s Qmini PCR can detect Hepatozoon DNA in 90 minutes at your clinics using blood as samples.

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