Ehrlichiosis is also refered to as canine rickettsiosis, canine hemorrhagic fever, canine typhus, tracker dog disease, and tropical canine pancytopenia. It is a tick-borne disease of dogs that is caused by the organism Ehrlichia. Dogs, cats, and in rare instances, humans are affected. German Shepherd dogs are known to be particularly affected by the disease. more...
There are several species of Ehrlichia, but the one that most commonly affects dogs and causes the most severe clinical signs is Ehrlichia canis. The brown dog tick, or Rhipicephalus sanguineous, that passes the Ehrlichia to the dog is prevalent throughout most of the United States, but most cases tend to occur in the Southwest and Gulf Coast regions where there is a high concentration of the tick.
Dogs get ehrlichiosis from the brown dog tick, which passes an ehrlichia organism into the bloodstream when it bites. There are three stages of ehrlichiosis, each varying in severity. The acute stage, occurring several weeks after infection and lasting for up to a month, can lead to fever and lowered peripheral blood cell counts. The second stage, called the subclinical phase, has no outward signs and can last for the remainder of the dog's life, during which the dog remains infected with the organism. In some dog breeds, such as the German Shepherd dog, the third and most serious stage of infection, the chronic phase, will commence. Very low blood cell counts (pancytopenia), bleeding, bacterial infection, lameness, neurological and ophthalmic disorders, and kidney disease, can result. Chronic ehrlichiosis can be fatal.
Antibiotics, administered for an extended period of time, are effective at eliminating the infection. Dogs with severe cases of chronic ehrlichiosis cannot be cured, but supportive care and treatment of diseases secondary to the infection, such as anemia, can help stabilize the dog.
Signs and symptoms
The acute stage of the disease, occurring most often in the spring and summer, begins one to three weeks after infection and lasts for two to four weeks. Clinical signs include a fever, petechiae, bleeding disorders, and vasculitis. There are no outward signs of the subclinical phase. Clinical signs of the chronic phase include pale gums due to anemia, bleeding due to thrombocytopenia, vasculitis, lymphadenopathy, respiratory dyspnea, coughing, polyuria, polydipsia, lameness, ophthalmic diseases such as retinal hemorrhage and anterior uveitis, and neurological disease. Dogs that are severely affected can die from this disease.
Although people can get ehrlichiosis, dogs do not transmit the bacteria to humans; rather, ticks pass on the ehrlichia organism. Clinical signs of human ehrlichiosis include fever, headache, eye pain, and gastrointestinal upset.
Diagnosis is achieved most commonly by serologic testing of the blood for the presence of antibodies against the ehrlichia organism. Many veterinarians routinely test for the disease, especially in enzootic areas. It should be noted, however, that during the acute phase of infection, the test can be falsely negative because the body will not have had time to make antibodies to the infection. As such, the test should be repeated. In addition, blood tests may show abnormalities in the numbers of red cells, white cells, and platelets, if the disease is present. Uncommonly, a diagnosis can be made by looking under a microscope at a blood smear for the presence of the ehrlichia organism, which sometimes can be seen within a white blood cell.
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