Ehrlichiosis in Dogs

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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.

    • Although rarely seen, the presence of organisms within the white blood cells is diagnostic for ehrlichiosis. Arrow points to a morula of Ehrlichia Canis in a white cell.

    Ehrlichiosis is a tick-borne disease caused by one of several organisms. It is most often transmitted through the bite of the brown dog tick. Although seen more often in the southeastern part of the United States, it has been reported throughout the country. It can occur in any age or breed of dog, and is most common in the German shepherd dog.

    Different phases of the disease are associated with different clinical signs. The acute (immediate) phase develops within 8 to 20 days after the parasite enters the body. This delay between infection and manifestation of clinical signs is called the incubation period. The acute phase often lasts for two to four weeks. In some dogs, the acute phase resolves spontaneously without the dog showing any clinical signs.

    Some dogs go on to develop a subclinical infection that persists for months. The parasite remains in these dogs, but no clinical signs are produced. The disease may also enter a chronic phase, which generally occurs two to three months after infection and can last for months to years. Dogs with chronic disease may show a variety of clinical signs. Ehrlichiosis may be associated with subtle nonspecific signs like lethargy, depression, anorexia and fever, or it can have a major impact on certain blood components, such as the platelets, red blood cells, and white blood cells. Decreased numbers of platelets (thrombocytopenia) are common and may be associated with life-threatening bleeding.

    There are several diseases or disorders that appear clinically similar to ehrlichiosis. These include:

  • Rocky Mountain spotted fever (RMSF) is another tick-borne rickettsial disease that can present with similar signs, especially in the early stages.

  • Immune-mediated thrombocytopenia is a disorder in which the body's immune system destroys it's own platelets. Thrombocytopenia is often seen in ehrlichiosis.

  • Systemic lupus erythematosus (SLE) is a disorder in which the body's immune system breaks down and affects many different systems in the body, such as the joints and kidneys.

  • Multiple myeloma is a malignant cancer of the white blood cell called the plasma cell. It may induce a high protein level in the blood, similar to ehrlichiosis.

  • Chronic lymphocytic leukemia, a type of cancer of white blood cells, may be confused with ehrlichiosis in cases that have certain changes in the bone marrow.

  • There are many other diseases that can cause bleeding problems, enlargement of the liver and spleen, and vague signs of fever and weight loss that must also be ruled out.

  • Diagnosis In-depth

    Certain diagnostic tests are required to make a definitive diagnosis of ehrlichiosis and to exclude other diseases that may cause similar symptoms. A complete history (travel pattern, exposure to ticks), description of clinical signs, and thorough physical examination are all-important to obtaining a tentative diagnosis. In addition, the following tests are recommended to confirm a diagnosis:

  • A complete blood count (CBC) may reveal anemia, and depending on the stage of disease, either a decreased or elevated white blood cell count. Finding the actual organism on a blood smear is rare, although when seen it is diagnostic for Ehrlichia.

  • A biochemical profile may reveal elevations in kidney and/or liver enzymes, electrolyte abnormalities, and elevated protein levels, particularly the globulin fraction.

  • A urinalysis may reveal excess protein in some dogs with ehrlichiosis.

  • A platelet count and full coagulation (clotting) profile are usually indicated, as thrombocytopenia is a common finding and other clotting tests may also be abnormal.

  • Chest and abdominal radiographs (X-rays) are an important part of any preliminary work-up. In some dogs they are normal. In other dogs they may reveal evidence of enlarged lymph nodes in the chest or abdomen, and enlargement of the liver and/or spleen. In addition, X-rays help to rule out other diseases and causes of the patients' clinical signs.

  • A bone marrow aspirate is the retrieval of a sample of bone marrow by passing a small needle into the core of one of the long bones, a small amount of marrow is withdrawn through a syringe and analyzed. 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. It also helps to rule out other disorders, such as multiple myeloma or chronic lymphocytic leukemia that can initially be difficult to differentiate from ehrlichiosis.

  • 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.

    Your veterinarian may recommend additional tests to exclude or diagnose concurrent conditions. These tests are not always necessary and are selected on a case-by-case basis. These tests include:

  • Serology for other tick born diseases such as Rocky Mountain spotted fever, Lyme disease, and babesiosis may be included in the same serologic test as for ehrlichiosis.

  • Abdominal ultrasonography may be recommended in certain cases. It is very helpful in evaluating all of the abdominal organs, including the liver, kidneys, lymph nodes and spleen. It is helpful in ruling out other disorders or diseases that may initially be difficult to differentiate from ehrlichiosis. Your veterinarian may refer your dog to a veterinary internal medicine specialist or a veterinary radiologist to have this test performed.

  • Serology for brucellosis is recommended in any male dogs that have scrotal and hind limb edema, as this is a clinical sign that can be seen with either disease.

  • Antinuclear antibody (ANA) tests may be performed in cases that are difficult to differentiate from systemic lupus erythematosus, an immune disorder that affects many organs and systems throughout the body.

    Therapy In-depth

    Patients with anemia (low red blood cell count) and/or bleeding from decreased platelet counts are most often hospitalized for supportive care. Animals that are not seriously ill are treated as outpatients, but require close monitoring, especially in the initial stages of therapy. With appropriate therapy, many dogs with acute disease do quite well. In more chronic cases, response to therapy can take longer and sometimes the response is poor. It is very important to follow all recommendations by your veterinarian very closely, and to address any questions or concerns that arise during the treatment protocol immediately.

  • Doxycycline, a synthetic derivative (manmade substance) of tetracycline, is the drug of choice. In cases where the dog is less than six months of age, chloramphenicol is recommended instead, as tetracycline drugs often stain the teeth of young growing puppies. Doxycycline is available in both intravenous and oral forms.

  • Other tetracycline antibiotics that may also be tried include tetracycline, oxytetracycline and minocycline. Tetracycline is available only in an oral form.

  • Intravenous fluid and electrolyte therapy may be indicated in dehydrated or debilitated patients.

  • Blood transfusions may be indicated for dogs with severe anemia and clotting abnormalities.

  • Tick control is of paramount important to prevent reinfection. Prevention is also possible by decreasing exposure of the dog to ticks. Tick infestation can be prevented by spot-on medications that are applied to the skin, 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.

  • Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your dog does not rapidly improve. Administer all prescribed medication as directed. Alert your veterinarian if you are experiencing problems treating your pet. Most antibiotics are given for at least two to three weeks for this disease.

    If abnormalities are detected initially in the blood count and platelet count, then it is common for these tests to be repeated every two to five days after initiating therapy, until the counts are back to normal. A biochemistry profile is initially repeated every four to 10 days, especially if abnormalities were detected on the original work-up.

    Serology may be repeated nine to 12 months after therapy. Most antibody titers peak between 2 and 5 months after infection, and then start to decrease if the parasite is eliminated from the body. A persistently high positive titer may represent reinfection or ineffective therapy, and may indicate the need for a second round of therapy.

    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.

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