Ehrlichiosis in Dogs

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Ehrlichiosis is a condition usually caused by Ehrlichia canis, which is a rickettsial organism spread by tick bites. Rickettsial organisms are bacteria that can only survive inside the cell of another living creature.

The brown dog tick, which carries the organism responsible for ehrlichiosis, transmits it to a dog within the saliva. Between one and three weeks later, the organism has incubated and may cause disease.

Ehrlichiosis Disease Process

Ehrlichiosis goes through three phases once a dog is infected:

• Acute stage. During this stage of the condition, the Ehrlichia organism spreads to the dog's spleen, liver, and lymph nodes. It causes injury to the platelets, which are a type of red blood cell that allows for normal clotting. It can also attack various kinds of white and red blood cells. Signs can include those listed in the next section. Some dogs clear the infection out at this stage while others enter the next stage. Some dogs don't show any signs of illness during the acute phase, and they may pass into the next without their owners knowing they're sick.
• Subclinical stage. During this stage of the condition, the organism stays in the dog's system, causing antibodies to continue circulating. The platelet count during this time often continues to be mildly to moderately low, and the dog might have trouble forming blood clots if the skin is punctured or there is some other injury. But, in general, dogs don't show signs of illness at this stage.
• Chronic stage. During this form of Ehrlichiosis, bone marrow production of platelets is negatively affected, so the dog is not producing enough of them. Dogs that don't clear the infection before the chronic stage develop many or all of the signs listed below.

Signs of Ehrlichiosis in Dogs

The course of the condition, from the acute phase through the chronic phase, often takes about two months. During the acute and chronic phases, the following signs may be evident:

• Lethargy
• Decreased or absent appetite
• Weight loss
• Fever
• Nosebleeds
• Difficulty breathing
• Wobbliness
• Head tilt
• Enlarged lymph nodes
• Bleeding in the retinas
• Swelling of the limbs
• Swelling of the scrotum in male dogs

Diagnosis of Ehrlichiosis

When a veterinarian suspects ehrlichiosis, he or she will also be considering other rickettsial diseases like Rocky Mountain spotted fever. Additionally, the doctor will be considering immune-mediated thrombocytopenia, systemic lupus erythematosus, multiple myeloma, leukemia, brucellosis, and other infections.

Bloodwork done on a dog in the acute phase of the condition could show decreased platelet levels, anemia, decreased white blood cell levels, and possibly increases in liver and kidney function values. During the chronic phase, reduced protein levels in the blood may occur as well as high kidney values.

Blood testing for antibodies to Ehrlichia may help diagnose the condition, especially if they are done serially, and an increase can be noted. There is also an in-clinic SNAP test that may be done for E.canis, but it's often negative until two to three weeks after exposure.

Additionally, the veterinarian may test for other conditions, such as brucellosis, to rule them out.

A bone marrow aspirate may help diagnose ehrlichiosis in dogs.

Treatment of Canine Ehrlichiosis

Treatment of this condition consists of stabilizing the patient medically. Blood transfusions that are platelet-rich may be necessary, and the dog could need fluid therapy for dehydration. Doxycycline, an antibiotic effective against Ehrlichia species, is given for at least four weeks. Other medications may be given as required for the dog's condition. Platelet levels will need to be monitored closely as the dog recovers.

Prevention of Ehrlichiosis in Dogs

Tick prevention and control is the best way to avoid Ehrlichia infections in dogs. If you live in an area that has brown dog ticks, which includes most of North America, ask your veterinarian what tick prevention medication is best for your dog. Even without brown dog ticks, other tick-borne illness are carried by other tick types, so ask your vet about prevention. Additionally, always check your dog for ticks after his been outside, and manually remove them using gloves if you find any.

The prognosis for ehrlichiosis in dogs is excellent with proper diagnosis and treatment.

Is Ehrlichiosis Zoonotic?

Ehrlichiosis can't be spread from infected dogs to people, but dogs can become infected by Ehrlichia directly from a tick. If dogs in a particular area are becoming infected, it means humans could too.

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