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Tick-Borne Disease in Dogs

Hepatozoonosis is a tick-borne disease that results in infection with the protozoan (one-celled organism) known as Hepatozoon americanum.

Symptoms and Types

The disease is more common in the southern and southeastern United States. Infection is often subclinical. However, symptoms of clinical infection include:

• Fever
• Lack of appetite
• Weight loss
• Bloody diarrhea
• Hyperesthesia (heightened sensitivity of the skin and musculature) over the back and sides
• Muscle wasting
• Proliferation of the outer layer (periosteum) of bones, causing pain
• Kidney failure

Hepatozoonosis may affect the bones, liver, spleen, muscles, small blood vessels in the heart muscle, and the intestinal tract.

Causes

Hepatozoonosis is carried by the tick Amblyomma maculatum. Dogs become infected through being bitten by an infected tick or through ingestion of an infected tick.

Diagnosis

Definitive diagnosis is made by finding the Hepatozoon organisms in white blood cells on a blood smear. However, routine blood testing consisting of a complete blood cell count and blood chemistry profile is typically performed in addition to the blood smear to check for additional organ dysfunction or abnormalities.

Radiographs (X-rays) to examine the bones of the pelvis, vertebrae, and legs may be recommended as well.

Treatment

Treatment is primarily palliative to relieve pain and may include glucocorticoids or non-steroidal anti-inflammatory medications. Initial combination therapy with trimethoprim/sulfa, clindamycin and pyrimethamine may be followed by long-term therapy with decoquinate.

Prevention

Hepatozoonosis in dogs can be prevented by controlling ticks and tick bites. It may be possible to remove an infectious tick before it has had a chance to pass the disease into the dog’s blood. Always check your dog after returning from an outing, and remove ticks carefully, thoroughly, and immediately.