Feline Infectious Anemia (Hemobartonellosis)

Feline Infectious Anemia (Hemobartonellosis)

By: Dr. Arnold Plotnick

Section: Veterinary Care In-depth

Diagnosis In-depth

Definitive diagnosis of hemotropic mycoplasmosis requires the demonstration of the organism on the patient's red blood cells. Other tests are performed to help assess the general health of the patient and help characterize any secondary conditions that might have led to the disorder, and to evaluate the effects that the disease is currently exerting on the patient.

  • Complete blood count (CBC). This is done to assess the extent of the anemia. Reticulocytes are immature red blood cells that are released from the bone marrow when certain types of anemias are present. A high reticulocyte count is expected in cases of anemia due to hemotropic mycoplasmosis, except in cases where the onset of the anemia is so rapid that the bone marrow has not had adequate time to release the reticulocytes into the circulation, or in cases where the bone marrow is depleted of red blood cell precursors due to feline leukemia virus infection.
    In the early, acute phase of infection, the total white blood cell count is normal or mildly elevated, with a higher percentage of neutrophils and monocytes.

  • Coomb's test. This test looks for antibodies that are directed against the body's own red blood cells. The antibodies cause agglutination (clumpingPerfect Litter Alert
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  • Serum chemistry panel. Chemistry panels are usually unremarkable. Anemic animals are less capable of delivering oxygen to the various body organs. The liver is especially susceptible to this decreased oxygen and mild elevations of the liver enzymes ALT and AST are occasionally seen. Sometimes, there is an elevated level of globulins; this is due to increased levels of antibodies in the circulation. A higher than normal level of bilirubin is also occasionally seen. Bilirubin is found in red blood cells. When red blood cells are destroyed at a faster than normal rate, as is the case in hemotropic mycoplasmosis, excessive amounts of bilirubin are released into the circulation. This is detected on a chemistry panel, and, if high enough, will be detected on physical examination as a yellow color imparted to the gums and the whites of the eyes.

  • Urinalysis. Urinalysis gives minimal information in hemotropic mycoplasmosis. Excessive amounts of hemoglobin or bilirubin in the urine reflect the red blood cell destruction that is commonly induced by Mycoplasma haemofelis.

  • Feline leukemia virus (FeLV) and Feline Immunodeficiency Virus (FIV) test. Infection with Mycoplasma haemofelis has been associated with FeLV infection and/or FIV infection. Up to 46 percent of cats infected with the organism have been found to be positive for FeLV in some reports, and approximately 40 percent of anemic cats infected with the FIV virus have been noted to be positive for Mycoplasma haemofelis. In other studies it was noted that cats infected with Mycoplasma haemofelis in conjunction with FeLV had more severe anemia than did cats infected with the parasite alone.

  • PCR analysis will detect the DNA of the parasite and is used to confirm the presence of Mycoplasma haemofelis in the blood.

  • Direct blood smear and microscopic analysis. This is the definitive test for diagnosing hemotropic mycoplasmosis and can be done by an outside laboratory or by the veterinarian directly. Because treatment may cause the organism to rapidly disappear from the circulation, all blood samples must be taken before any treatment is administered. Blood is taken, preferably directly from a vein, and a drop is put immediately on a slide. A thin blood smear is made, stained, and examined under the microscope. Mycoplasma haemofelis organisms appear as uniform small dark blue or purple entities attached to the red blood cell surface, usually on the edges of the cells.

    Cats infected with hemotropic mycoplasmosis experience phases where the parasite is present in the bloodstream (parasitemic phase), alternating with phases where no organism is present (non-parasitemic phase). A negative test may not necessarily mean that the organism is not present; it may just mean that the blood has been sampled during one of the "non-parasitemic" phase. Daily sampling may be necessary for a few days before organisms are found in some cats.

    Therapy In-depth

    Therapy is designed to control the parasite and to stop the destruction of red blood cells. Animals that are severely anemic from the disorder may need immediate intervention to stabilize them before chronic therapy.

  • Antibiotics. Feline hemotropic mycoplasmosis is most frequently treated with oral or injectable tetracyclines. Tetracycline, oxytetracycline, enrofloxacin and doxycycline are all reported to be effective. Doxycycline has the fewest side effects of the tetracyclines described. Treatment causes disappearance of the organism from the red blood cells and improvement in clinical signs, although the organism is probably not eliminated from the cat, and cats are said to remain "carriers" for life. Treatment usually lasts three weeks.

  • Corticosteroids. The use of corticosteroids is controversial in some circles. Some veterinarians recommend using a glucocorticoid like prednisolone immediately, while others wait to see if antibiotic therapy alone causes the anemia to resolve. If there is evidence of red blood cell destruction, such as a positive Coomb's test, agglutination of red blood cells on a microscope slide, or the presence of spherocytes – a type of red blood cell that indicates destruction of the body's own red blood cells by the immune system, prednisolone therapy should begin immediately.

  • Blood transfusion. Clinical judgment should determine whether a blood transfusion is necessary. The hematocrit, which is the percentage of the blood that is comprised of red blood cells, is not the absolute determinant of whether a patient needs a blood transfusion. The clinical signs are equally important determinants. Cats who are mildly affected, even with hematocrit levels of 12 to 15 percent (normal is 24 to 44 percent) probably will not require a transfusion. Most cats with hematocrit levels less than 12 percent will indeed need a blood transfusion. Your veterinarian will decide whether a transfusion is necessary.

  • Supportive care. Intraveous fluids may be needed in patients that are dehydrated. Nutritional support including tube feeding may be required in cats that are not eating.

    Prognosis

    The prognosis depends on the severity of the disease and response to treatment. The prognosis is generally considered good when treated aggressively with antibiotics, blood transfusions if needed and additional supportive care.

     
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