Canine ehrlichiosis is usually caused by Ehrlichia canis bacteria, though other types of Ehrlichia bacteria can also cause this disease. These bacteria belong to a group called rickettsiae, which are a special kind of bacteria that can only live inside other cells.
Once inside the dog’s body, the bacteria infect a type of white blood cell, leading to fever and other symptoms. A related organism, Ehrlichia ewingi, infects a different type of white blood cell. It has been found in both dogs and people in the southern, western, and midwestern United States.
Another similar bacterium, Anaplasma platys, causes a condition in dogs called infectious cyclic thrombocytopenia. This disease leads to repeated drops in the levels of platelets (the fragments in blood that stick together to form clots), which can interfere with normal blood clotting. Anaplasma phagocytophilum causes anaplasmosis in people and can also make dogs sick. In the United States, it most commonly affects people in the Northeast, upper Midwest, and western regions.
Ehrlichia and Anaplasma bacteria are found in many parts of the world. They are spread by ticks—such as the brown dog tick, lone star tick, and black-legged tick—which become infected after biting infected animals.
Dogs are the main animals affected by these bacteria, but people, cats, and other domestic animals can sometimes become infected as well.
Infections caused by Ehrlichia canis can start as sudden illness but can progress to long-term disease. How severe the infection becomes depends on the strain of the bacteria and the response of the dog’s immune system.
In the early stage of infection, common signs include:
fever
swollen lymph nodes
enlarged spleen
low blood platelet count
Other possible symptoms are:
loss of appetite
low energy
stiffness or reluctance to walk
swelling in the legs or scrotum
coughing or trouble breathing
Most short-term cases happen during warmer months when ticks are more active. During this stage, death is rare, and some dogs recover on their own. After recovery, a dog might stay healthy—or the disease can progress into a long-term form.
Long-term ehrlichiosis caused by Ehrlichia canis can occur in any dog, but some breeds—especially German Shepherd Dogs—are more likely to develop it. Unlike the early stage, this long-term form is not related to the season.
Symptoms in long-term infections depend on which parts of the body are affected. They can include:
enlarged spleen
kidney failure
inflammation in the lungs, eyes, brain, or spinal cord
If the brain or spinal cord is affected, dogs can show nervous system problems such as:
poor coordination
weakness
partial paralysis (inability to move)
increased sensitivity to touch
Other common signs include:
severe weight loss
low platelet levels (needed for blood clotting)
low levels of other blood cells
Because platelets help the blood clot, dogs with very low platelet levels might have:
nosebleeds
blood in urine or feces
increased tendency to bruise (seen most often on the skin or gums)
Dogs infected with Anaplasma platys usually show few or no symptoms, even though the bacteria infect their platelets and cause periodic drops in platelet levels.
Infections with other bacteria in the rickettsiae family tend to cause signs similar to those seen in the early (short-term) stage of Ehrlichia canis infection, but these illnesses are usually milder and resolve on their own.
Common signs of other rickettsial infections can include:
fever
lameness that shifts from one leg to another
Long-term disease isn't usually seen with these other infections, unlike with Ehrlichia canis.
Diagnosis is made with blood tests.
Treatment is usually a course of antibiotics. For short-term infections, fever often improves soon after treatment starts. In long-term cases, blood changes can take months to fully resolve. Severe bleeding can require blood or platelet transfusions.
Tick control is most important to prevent infection, so:
Avoid tick-heavy areas when possible.
Use veterinarian-recommended products to prevent ticks.
Remove ticks promptly with fine tweezers, grasping close to the skin and pulling straight out.
Some rickettsial bacteria can infect people, but ticks spread the bacteria when they bite people and animals. An infected dog signals that ticks (and tickborne disease risk) are present in the area.
For More Information
Also see professional content regarding ehrlichiosis.
