What Is Canine Granulocytic Ehrlichiosis?
Canine granulocytic ehrlichiosis is an infectious disease affecting dogs, caused by bacteria such as Anaplasma phagocytophilum and Ehrlichia ewingii. These pathogens target neutrophils, a type of white blood cell, and are transmitted through tick bites. The disease is not directly contagious between dogs.
While more prevalent in the southeastern and south-central United States, cases have been reported in Quebec, particularly in the Eastern Townships, where the Lone Star tick (Amblyomma americanum) has been identified.
How the Infection Spreads
Transmission occurs when infected ticks, such as Ixodes scapularis for Anaplasma and Amblyomma americanum for Ehrlichia, attach to a dog and feed on its blood. The bacteria are typically transmitted within 24 to 48 hours of attachment. Once inside the host, the bacteria invade neutrophils and disseminate to organs like the spleen, liver, and lymph nodes. The incubation period ranges from one to two weeks.
Clinical Signs to Watch For
Common symptoms include:
- Joint swelling and pain leading to lameness
- Fever
- Loss of appetite
- Lethargy or depression
- Nasal and ocular discharge
- Abdominal discomfort
- Enlarged lymph nodes
- Abnormal gait
Some dogs may exhibit mild or no symptoms, making the disease challenging to detect without testing.
Diagnosing Ehrlichiosis
Diagnosis involves a combination of specific and general tests:
Specific Tests:
- Microscopic examination of a blood smear (may yield false negatives)
- Serological tests to detect antibodies, with follow-up testing after 2–4 weeks
- PCR tests to identify bacterial DNA
General Tests:
- Complete blood count revealing low platelet and neutrophil counts, anemia, or elevated white blood cells
- Ophthalmic examination for retinal hemorrhages or detachment
- Abdominal radiographs to assess spleen size
- Lymph node aspiration if enlargement is present
- Joint fluid analysis in cases of joint swelling
- Bone marrow aspiration if platelet counts are persistently low
- Cerebrospinal fluid analysis if neurological signs are observed
Treatment Options
The primary treatment is a 2–3-week course of antibiotics, typically doxycycline. Supportive care may include:
- Blood transfusions for severe anemia
- Pain management medications
- Intravenous fluids for hydration
Most dogs respond well to treatment, especially when initiated promptly.
Preventing Infection
Effective tick control is crucial:
- Use veterinarian-recommended tick preventatives
- Regularly inspect your dog for ticks, especially after outdoor activities
- Avoid areas with high tick populations when possible
Consult your veterinarian to determine the most appropriate tick prevention strategy for your dog.
Prognosis
With early detection and appropriate treatment, the prognosis is generally favorable. However, complications can arise if the disease progresses or if secondary infections occur.
Can Humans Contract Ehrlichiosis from Dogs?
Humans cannot contract ehrlichiosis directly from dogs. However, ticks that have fed on infected dogs can transmit the bacteria to humans. Therefore, tick prevention is essential for both pets and their owners.
