Ehrlichiosis in Cats
Dr. Rhea Morgan
Ehrlichiosis is an uncommon tick-born disease of cats that is caused by one of several rickettsial organisms that belong to the genus, Ehrlichia. Ehrlichia canis (E. canis) and Ehrlichia risticii (E. risticii) are believed to be the primary causative agents in the cat. Lethargy, depression
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 has been detected in cats in the United States, Europe, South America, Africa, and the Far East.
How cats acquire the disease is not well understood. Ticks have been identified on some infected cats. Although the pattern of development of the disease in cats is not well known, it is believed to be similar to ehrlichiosis in dogs.
What to Watch For
Anorexia (decreased appetite), weight loss
Vomiting and diarrhea
Pale mucous membranes from anemia
Swollen glands (enlarged lymph nodes)
Swollen and inflamed joints
Discharge from the eyes and inflammation inside the eyes
A complete blood count (CBC), platelet count, biochemical profile, and urinalysis are indicated for all suspect cases. Abnormal findings may include anemia, which is a low platelet count and low counts for some or all of the white blood cells. Platelets are small particles in the blood responsible for initiating a blood clot. Other findings may include elevated protein levels in the blood, evidence of the presence of another blood parasite, Haemobartonella felis, and evidence of lymphosarcoma, a cancer of white blood cells.
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 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. Evidence of lymphosarcoma may also be found in the bone marrow.
Serologic testing detects various antibodies produced by the body against Ehrlichia. Sometimes these antibodies are detected in cats, yet they do not always correlate well with the presence of active infection in cats.
Ehrlichia polymerase chain reaction (PCR) is a test that is capable of detecting the presence of extremely small amounts of the parasite. Some cats that are negative on serologic testing may be positive with the PCR test. A positive PCR test usually confirms the diagnosis.
Confirmation of the disease in cats may also require culturing of the organisms from a blood sample.
Depending on the severity of clinical signs, treatment options may include out patient care or may necessitate hospitalization. Antibiotic therapy is the mainstay of treatment for ehrlichiosis in cats. 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. Presently, doxycycline is the preferred drug to use for ehrlichiosis because it is well tolerated in cats. Tetracycline and oxytetracycline may cause anorexia, fever and lethargy in some cats.
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 is excellent if the disease is caught early. Most cats show improvement within 72 hours of starting the antibiotics. The prognosis for severely ill cats, or for cats with accompanying feline hemotropic mycoplasmosis and lymphosarcoma is poor.
Although the method of transmission of ehrlichiosis in cats is unknown, prevention of tick and flea infestation is recommended. Tick and flea infestation can be prevented by spot-on medications that are applied to the skin, and with sprays or powders. Cats are highly susceptible to insecticides that prevent fleas and ticks. Products designed for use in dogs may be severely toxic to cats, and may result in seizures, collapse, coma, and death. It is important to obtain tick and flea preventive medications from your veterinarian, and to make sure the product labeled as being safe for use in cats.