Ehrlichiosis – Tick Fever

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Ehrlichiosis also known as Tick Fever , canine rickettsiosis, canine hemorrhagic fever is a tick-borne disease of dogs usually caused by the organism Ehrlichia canis. Cats can also be infected.


When Dogs get Sick

There are three phases of illness with Ehrlichiosis:

  1. ACUTE PHASE: This is generally a mild phase and occurs 1 to 3 weeks after the host is bitten by the tick. The Ehrlichia organism is replicated in this time period and attaching to white blood cell membranes. During this time the platelet count will drop and platelet destruction will occur. The dog will be listless, off food, and may have enlarged lymph nodes. There may be fever as well but rarely does this phase kill a dog. Most dogs clear the organism if they are treated in this stage but those that do not receive adequate treatment will go on to the next phase.
  2. SUBCLINICAL PHASE: In this phase, the dog appears normal. The organism has sequestered in the spleen and is essentially hiding out there. Dogs can stay in this phase for months or even years. The only hint that Ehrlichia is hiding is a somewhat reduced platelet count and/or elevated globulin level on a blood test.
  3. CHRONIC PHASE: In this phase the dog gets sick again. Up to 60% of dogs infected with Ehrlichia canis will have abnormal bleeding due to reduced platelets numbers.


Diagnosis is achieved most commonly with a blood test for the presence of antibodies against the ehrlichia organism. In addition, blood tests may show abnormalities in the numbers of red blood cells, white blood cells, and most commonly platelets, if the disease is present.

Treatment of Ehrlichiosis

The antibiotics, tetracycline or doxycycline are used. (Doxicycline at 11 mg/kg). Treatment is usually for 3-4 weeks, even though the dog’s symptoms generally improve after several days of therapy. Some dogs will need blood transfusions or intravenous fluids depending on the severity of the disease. Generally, the prognosis during the acute phase is good, if the animal is properly treated. Dogs who go on to the chronic phase have a poorer prognosis. German Shepherds and Doberman Pinschers tend to have a more severe chronic form of the disease.

Prevention of Ehrlichiosis

Tick control is the main way to prevent Ehrlichiosis. Products which repel and kill ticks such as those containing permethrins are excellent choices. Tick collars containing the active ingredient amitraz (Preventic collars) are also used, sometimes in conjunction with permethrin products in those areas with high tick infestations. There is no vaccine for ehrlichiosis.

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