Issue Description Dogs get ehrlichiosis from the brown dog tick,
which passes an ehrlichia organism into the bloodstream when it bites.
It is also possible for dogs to become infected through a blood
transfusion from an infected dog. 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 due to bone marrow
suppression. 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. Some dogs are able
to successfully eliminate the disease during this time. In some dogs
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. Other Names Ehrlichiosis, Canine Rickettsiosis, Canine Typhus, Tracker Dog Disease, Canine Hemorrhagic Fever
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, vasculitis, lymphadenopathy,
discharge from the nose and eyes, and edema of the legs and scrotum.
There are no outward signs of the subclinical phase. Clinical signs of
the chronic phase include weight loss, pale gums due to anemia,
bleeding due to thrombocytopenia, vasculitis, lymphadenopathy,
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. It is quite similar to Rocky
Mountain spotted fever, but rash is not seen in patients.
Diagnosis 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 blood cells,
white blood cells, and most commonly 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 morulae,
which sometimes can be seen as intracytoplasmic inclusion bodies
within a white blood cell.
Treatment Supportive care must be provided to animals
that have clinical signs. Subcutaneous or intravenous fluids are given
to dehydrated animals, and severely anemic dogs may require a blood
transfusion. Treatment for ehrlichiosis involves the use of
antibiotics such as tetracycline or doxycycline for a period of at
least six to eight weeks; response to the drugs may take one month. In
addition, steroids may be indicated in severe cases in which the level
of platelets is so low that the condition is life threatening.
Prognosis The prognosis is good for dogs with acute
ehrlichiosis. For dogs that have reached the chronic stage of the
disease, the prognosis is guarded. When bone marrow suppression occurs
and there are low levels of blood cells, the animal may not respond to
Prevention Tick control is the most effective method of
prevention, but tetracycline at a lower dose can be given daily for
200 days during the tick season in endemic regions.