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Ehrlichiosis in Dogs

Ehrlichiosis in dogs is a rickettsia infection caused by the organisms Ehrlichia canis and Ehrlichia lewinii. These bacteria are spread by the brown dog tick and the Lone Star tick, respectively. Rickettsiae are a type of bacteria that inhabit a cell, in this case, the body's white blood cells, which are destroyed in the process.

While there are a number of species in the genus Ehrlichia, the E. canis and E. lewinii are the two that are of main concern for dogs, with E. canis being the more diagnosed form (note that these bacteria can infect other animals as well, including humans). This disease is seen throughout the year and throughout the continental U.S., but is more common on the Gulf Coast, eastern seaboard, Southwest and California, geographical areas that tend to have an abundance of warm days. Chronic and severe forms of this disease are more representative in Doberman pinschers and German shepherds.

Symptoms and Types

There are three stages of Ehrlichiosis:

Acute stage:

• Symptoms present around 1-3 weeks after bite from infected tick
• Enlarged lymph nodes
• Weakness
• Lethargy
• Depression
• Lack of appetite
• Difficult respiration
• Limb edema

Subclinical stage:

• Bacteria may be present for months or years without clinical symptoms

Chronic Stage:

• Abnormal bleeding
• Nose bleed
• Severe weight loss
• Fever
• Trouble breathing due to inflammation of the lungs
• Joint inflammation and pain
• Seizures in some animals
• Lack of coordination
• Head tilt
• Eye pain
• Anemia
• Kidney failure
• Paralysis

Diagnosis

You will need to provide a thorough history of your dog's health leading up to the onset of symptoms, including recent activities, and the environment your dog spends time in. It goes without saying that if your dog has recently been bitten by a tick, you will need to share this information with your veterinarian.

Along with the standard fluid tests, complete blood count (CBC), biochemistry profile, and urinalysis, your veterinarian will also need to carry out more specific tests for isolating E. canis. Polymerase Chain Reaction (PCR) testing, which isolates the DNA of the causative agent, is now commonly employed for confirmation. The PCR test, in combination with a test for antibodies to the Ehrlichia infection, is typically the best way to make a concrete diagnosis.

Typically, ehrlichiosis will cause a decreased number of platelets (the cells involved in the clotting of blood), a condition referred to as thrombocytopenia. There will also be a decreased number of neutrophils (a type of white blood cell), anemia, and an increased number of lymphocytes (a type of white blood cell usually seen in advanced infections). The urinalysis may reveal the presence of proteins in urine, which result from inflammation of the kidneys.

Other indications your veterinarian will look for are hemorrhages within the retina of the eye, inflammation of the lungs, an enlarged spleen, and inflammation of the brain or spinal cord. If nervous symptoms are present, such as a lack of coordination or seizures, your veterinarian may take a sample of cerebrospinal fluid (CSF) for further evaluation.