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Ehrlichia Infection

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Ehrlichia are bacteria that were discovered by a doctor of the same name. Ehrlichia live in the white blood cells of their host which can be human or animals. They are spread between hosts by tick bites and because they are located in the centre of white blood cells they can be very difficult to kill. Traditional antibiotics will not penetrate a cell membrane in order to kill bacteria living within. There are different kinds of Ehrlichia which live in different kinds of white blood cells. Ehrlichia equi live in granulocytes; Ehrlichia ewingii are another type that live in granulocytes; Ehrlichia canis and Ehrlichia ristici live in monocytes; and Ehrlichia platys live in platelets which are responsible for blood clotting. These classifications are not absolute however and should just stand as guidelines.

More current classifications of Ehrlichia include Ehrlichia canis and Ehrlichia ewingii which are mostly responsible for infections in dogs; Ehrlichia chaffeensis which are mostly responsible for infections in humans; and Ehrlichia ruminatium. Ehrlichia are passed through Brown Dog Ticks and some other types of ticks depending on the region. Ehrlichia in animals is usually transmitted via the Brown Dog Tick.

Symptoms and Diagnosis

The symptoms of Ehrlichia infection involve a number of phases. In the acute phase, symptoms are mild and begin between 1 and 3 weeks after the animal is bitten by the tick. Ehrlichia reproduce during this period and attach to the membranes of white blood cells. This causes a reduction in platelet count and your pet will be lethargic, disinterested in food, and may have swollen lymph nodes.

During the subclinical phase your pet will not appear to have any symptoms. The Ehrlichia has made its way to the spleen where it lies dormant. This phase can actually last several months and even years and the only indications of Ehrlichia infection would be seen in blood tests (reduced platelet count and increased globulin levels). Finally, during the chronic phase you will notice that your pet develops illness. Most animals will have difficulty with blood clotting because of reduced platelet counts. This means that after sustaining injury your pet will bleed for abnormal amounts of time. Inflammation of the eyes and some neurological effects may also be present. Glomerulonephritis is a common side effect as well.

Diagnosis requires results from a variety of tests. Firstly, your dog will exhibit a fever, enlarged lymph nodes, abnormal bleeding, and arthritis and your veterinarian will want to identify these symptoms first. Next, blood tests to determine platelet and globulin levels will need to be conducted. Finally, the ultimate diagnosis will rely on a blood test to determine if the antibody against Ehrlichia is present in your pet’s system.


Tetracycline is currently seen as the most effective antibiotic against Ehrlichia but a more modern intracellular antibiotic that is also common is Doxycycline. Treatment usually runs for about a month but you should expect your pet to show immediate improvement. If there are other immune-related secondary diseases such as arthritis then corticosteroids are also commonly prescribed by veterinarians.

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