Ehrlichiosis in Dogs

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Ehrlichiosis in Dogs

By: Dr. Bari Spielman

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Section: Veterinary Care In-depth

Diagnosis In-depth

Certain diagnostic tests are required to make a definitive diagnosis of ehrlichiosis and to exclude other diseases that may cause similar symptoms. A complete history (travel pattern, exposure to ticks), description of clinical signs, and thorough physical examination are all-important to obtaining a tentative diagnosis. In addition, the following tests are recommended to confirm a diagnosis:

A complete blood count (CBC) may reveal anemia, and depending on the stage of disease, either a decreased or elevated white blood cell count. Finding the actual organism on a blood smear is rare, although when seen it is diagnostic for Ehrlichia.

A biochemical profile may reveal elevations in kidney and/or liver enzymes, electrolyte abnormalities, and elevated protein levels, particularly the globulin fraction.

A urinalysis may reveal excess protein in some dogs with ehrlichiosis.

A platelet count and full coagulation (clotting) profile are usually indicated, as thrombocytopenia is a common finding and other clotting tests may also be abnormal.

Chest and abdominal radiographs (X-rays) are an important part of any preliminary work-up. In some dogs they are normal. In other dogs they may reveal evidence of enlarged lymph nodes in the chest or abdomen, and enlargement of the liver and/or spleen. In addition, X-rays help to rule out other diseases and causes of the patients' clinical signs.

A bone marrow aspirate is the retrieval of a sample of bone marrow by passing a small needle into the core of one of the long bones, a small amount of marrow is withdrawn through a syringe and analyzed. Examination of the bone marrow helps to determine why certain blood cells are decreased in the blood count and provides information on whether the bone marrow is healthy enough to recover. It also helps to rule out other disorders, such as multiple myeloma or chronic lymphocytic leukemia that can initially be difficult to differentiate from ehrlichiosis.

Serologic testing detects various antibodies produced by the body against Ehrlichia. Antibodies are often detected within seven days of exposure and infection with the organism and may persist for months. It is sometimes difficult to determine whether the antibody titers present in the dog are due to chronic exposure to the disease because the dog lives in areas where infected ticks are prevalent, or whether the titers indicate there is active infection present in the dog.

Ehrlichia polymerase chain reaction (PCR) is a test that is capable of detecting the presence of extremely small amounts of the parasite.

Your veterinarian may recommend additional tests to exclude or diagnose concurrent conditions. These tests are not always necessary and are selected on a case-by-case basis. These tests include:

Serology for other tick born diseases such as Rocky Mountain spotted fever, Lyme disease, and babesiosis may be included in the same serologic test as for ehrlichiosis.

Abdominal ultrasonography may be recommended in certain cases. It is very helpful in evaluating all of the abdominal organs, including the liver, kidneys, lymph nodes and spleen. It is helpful in ruling out other disorders or diseases that may initially be difficult to differentiate from ehrlichiosis. Your veterinarian may refer your dog to a veterinary internal medicine specialist or a veterinary radiologist to have this test performed.

Serology for brucellosis is recommended in any male dogs that have scrotal and hind limb edema, as this is a clinical sign that can be seen with either disease.

Antinuclear antibody (ANA) tests may be performed in cases that are difficult to differentiate from systemic lupus erythematosus, an immune disorder that affects many organs and systems throughout the body.

Therapy In-depth

Patients with anemia (low red blood cell count) and/or bleeding from decreased platelet counts are most often hospitalized for supportive care. Animals that are not seriously ill are treated as outpatients, but require close monitoring, especially in the initial stages of therapy. With appropriate therapy, many dogs with acute disease do quite well. In more chronic cases, response to therapy can take longer and sometimes the response is poor. It is very important to follow all recommendations by your veterinarian very closely, and to address any questions or concerns that arise during the treatment protocol immediately.

Doxycycline, a synthetic derivative (manmade substance) of tetracycline, is the drug of choice. In cases where the dog is less than six months of age, chloramphenicol is recommended instead, as tetracycline drugs often stain the teeth of young growing puppies. Doxycycline is available in both intravenous and oral forms.

Other tetracycline antibiotics that may also be tried include tetracycline, oxytetracycline and minocycline. Tetracycline is available only in an oral form.

Intravenous fluid and electrolyte therapy may be indicated in dehydrated or debilitated patients.

Blood transfusions may be indicated for dogs with severe anemia and clotting abnormalities.

Tick control is of paramount important to prevent reinfection. Prevention is also possible by decreasing exposure of the dog to ticks. Tick infestation can be prevented by spot-on medications that are applied to the skin, sprays, collars, and dips. Avoid tick-infested areas, and remove ticks as soon as possible, as they must be attached for a minimum of 24 to 48 hours in order to transmit the disease.

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