Ehrlichiosis in dogs is caused by infection with specific bacteria that are transmitted through the bites of ticks and cause the body to attack and destroy a type of cell that helps blood to clot. Different types of Ehrlichia bacteria can cause disease in dogs and in other species of animals, but Ehrlichia canis and Ehrlichia ewingii are responsible for most canine infections. Ehrlichiosis is commonly diagnosed in areas where ticks are prevalent.
Symptoms of ehrlichiosis can include fever, lethargy, enlarged lymph nodes, limping, bruising and bleeding, which may not be immediately apparent if it occurs internally. Chronic eye inflammation and neurologic abnormalities may also be seen. In order to diagnose ehrlichiosis and differentiate it from other diseases that cause similar symptoms (e.g., Rocky Mountain Spotted Fever, Lyme disease, lymphosarcoma and immune disorders) and to plan appropriate treatment, veterinarians will often order blood cell counts, chemistry panels and tests that can determine whether or not an animal has been exposed to Ehrlichia bacteria. Infected dogs will sometimes develop clinical signs of the disease long after being bitten by a tick, so a lack of recent tick exposure does not rule out a diagnosis of ehrlichiosis.
Certain types of antibiotics are very effective against Ehrlichia bacteria, and once treatment begins, an affected animal's condition will usually improve rapidly. In more severe cases, blood transfusions or medications limit the body's immune response against its own blood cells may be necessary. Many cases of ehrlichiosis can be prevented through the use of effective tick control products. Dogs that have contracted the disease once do not have immunity against subsequent infections.
Written by: Jennifer Coates, DVM
Last reviewed: October 2, 2008