Ehrlichiosis in Dogs

Ehrlichiosis is a tick-born disease of dogs characterized by fever, lethargy, lameness and/or bleeding tendencies. It is caused by one of several rickettsial organisms that belong to the genus, Ehrlichia. Ehrlichia canis (E. canis) is the primary causative agent in dogs.

Rickettsia are small microscopic organisms that are different from both bacteria and viruses. They enter various cells of the body and behave as tiny parasites, eventually killing the cell. Ehrlichiosis occurs worldwide, and it achieved prominence during the Vietnam War, when a large proportion of military dogs contracted the disease.

The disease is spread predominantly by the brown dog tick in the United States. Ticks are seen on the affected dog less than half the time, however. Infrequently, ehrlichiosis can be caused by the transfusion of infected blood. It occurs much more commonly in the dog than in the cat.

It can be seen in any age dog, although it is seen most commonly in middle-aged animals. Purebred dogs, especially German shepherd dogs, appear to be more susceptible than crossbred dogs.

The impact on the affected individual can vary from very mild clinical signs to severe, life threatening disease. Several different stages of the disease are possible. Subclinical, asymptomatic infection may occur and may persist for months or years. Acute clinical signs may develop in some dogs and resolve spontaneously or with treatment. Acute infections may also develop into chronic infections that produce more severe clinical signs.

What to Watch For

Lethargy, depression

Anorexia (decreased appetite), weight loss

Fever

Spontaneous bleeding from any part of the body (urine, stool, nose)

Bruising or small hemorrhages in the skin, gums, lips or around the eyes

Breathing difficulty

Neurologic signs (poor balance, difficulty walking, tremors, seizures)

Squinting and inflammation of the eye, decreased vision

Swollen glands (enlarged lymph nodes)

Swollen and inflamed joints

Diagnosis

A complete blood count (CBC), platelet count, biochemical profile, and urinalysis are indicated for all suspect cases. Depending on the stage of the disease, abnormal findings may include anemia, low platelet count (Platelets are small particles in the blood responsible for initiating a blood clot.), and low counts for some or all of the white blood cells. Elevations in kidney and/or liver values, elevated or decreased protein levels in the blood, and protein in the urine may also be found.

Although rarely seen, the presence of organisms within the white blood cells is diagnostic for ehrlichiosis.

Screening chest and abdominal radiographs (X-rays) may be performed. Although within normal limits in many cases, they may reveal an enlarged liver or spleen. They also help to rule out other diseases that produce similar clinical signs.

A full blood clotting panel may be performed. Other clotting tests beside the platelet count may be abnormal.

A bone marrow aspirate may be recommended. Examination of the bone marrow helps to determine why certain blood cells are decreased in the blood count and provides information on whether the bone marrow is healthy enough to recover.

Serologic testing detects various antibodies produced by the body against Ehrlichia. Antibodies are often detected within seven days of exposure and infection with the organism, and may persist for months. It is sometimes difficult to determine whether the antibody titers present in the dog are due to chronic exposure to the disease because the dog lives in areas where infected ticks are prevalent, or whether the titers indicate there is active infection present in the dog.

Ehrlichia polymerase chain reaction (PCR) is a test that is capable of detecting the presence of extremely small amounts of the parasite.

Treatment

Depending on the severity of clinical signs, treatment options may include outpatient care or may necessitate hospitalization. Antibiotic therapy is the mainstay of treatment for ehrlichiosis. In severely ill patients, intravenous fluid therapy, blood transfusions, and other forms of intensive support may be indicated.

The most common antibiotics used to treat ehrlichiosis belong to the tetracycline family of drugs. They include doxycycline, tetracycline, oxytetracycline, and minocycline. These antibiotics have the greatest efficacy against Ehrlichia, and the fewest side effects.

Home Care and Prevention

At home, be sure to administer all medication exactly as prescribed and return for follow-up testing as directed by your veterinarian. Most antibiotics are given for at least two to three weeks for this disease. Prognosis with acute disease is excellent if caught early. Dogs in the acute phase of the disease often show improvement within 72 hours of starting the antibiotics. The prognosis with chronic cases varies, and dogs with chronic disease may require prolonged treatment.

Be aware that although uncommon, ehrlichiosis has been reported in people. It is felt that human transmission probably occurs through the bite of a tick, and is not caught from an infected dog.

Prevention is possible by decreasing exposure of the dog to ticks. Tick infestation can be prevented by spot-on medications that are applied to the skin, with sprays, collars, and dips. Avoid tick-infested areas, and remove ticks as soon as possible, as they must be attached for a minimum of 24 to 48 hours in order to transmit the disease.