Feline Infectious Anemia (Hemobartonellosis)

Overview of Feline Infectious Anemia

Feline infectious anemia, also known as hemobartonellosis or feline hemotropic mycoplasmosis, is a parasitic disease of worldwide significance. Affected cats experience some degree of anemia is a parasitic disease of worldwide significance. Affected cats experience some degree of anemia, although it also causes a wide range of other clinical signs that can vary from simple depression and lethargy to fever and shock.

Below is an overview of feline infectious anemia followed by in-depth information about the diagnosis and treatment options for this disease.

The causative organisms for this disease are Mycoplasma haemofilis previously called Hemobartonella felis large form and Mycoplasma haemominutum previously called Haemobartonella felis small form. They are parasites that affects the outer surface of feline red blood cells. The name of the parasite was changed after extensive study when it was determined that the parasite was genetically similar to other mycoplasma organisms.

Cats of all ages and breeds can be affected. There are several predisposing risk factors for feline hemotropic mycoplasmosis, including the presence of another disease that causes immunosuppression such as cancer or feline leukemia virus (FeLV), deficient vaccination status, history of cat bite abscesses within prior few weeks and cats that have exposure to fleas and ticks. Young intact male cats are at increased risk due to fighting and roaming behaviors.

The primary mode of transmission is by blood sucking arthropods such as fleas, ticks and possibly mosquitoes.

The impact of the disease varies widely. Some cases are mild, while other cases can be associated with severe weakness, depression anorexia, fever, weight loss, anemia, and sometimes death.

What to Watch For

• Weakness (sudden or gradual)
• Pale or yellow-tinged mucous membranes in the gums, nose
• Fever
• Diffuse whole-body tenderness
• Rapid breathing rate (tachypnea)
• Weight loss
• Fever

Diagnosis of Feline Infectious Anemia

• Complete blood count including reticulocytes
• Coombs test
• Chemistry panel
• Urinalysis
• Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) testing
• Direct blood smear and microscopic analysis
• PCR analysis. This is the best test to confirm the presence of Mycoplasma haemofelis infection.

Treatment of Feline Infectious Anemia

• Antibiotics. Mycoplasma haemofelis is typically susceptible to tetracycline and doxycycline.
• Corticosteroids, although controversial are used in selected cases
• Blood transfusion in cases of severe anemia

Home Care and Prevention

Carefully monitor your cat during treatment. Administer medications as prescribed and notify your veterinarian if you are having trouble giving the medication. Recheck appointments are very important to make sure your cat continues to improve.

Keeping your cat indoors can help prevent exposure to possible vectors of infection, reduced fighting between cats and reduced exposure to various diseases and viruses. Neuter outside cats to reduce the risk of cat fights. Use medications to prevent fleas and ticks.

In-depth Information about Feline Infectious Anemia

Feline hemotropic mycoplasmosis is an infectious disease caused by the parasite Mycoplasma haemofelis. It causes hemolytic anemia, a type of anemia where the body destroys its own red blood cells because they “look different” to the immune system. The disease was first described in the United States in 1953.

The causative agent, Mycoplasma haemofelis, is a parasite that affects the surface of feline red blood cells. A large study performed in 1990 helped establish the prevalence of Mycoplasma haemofelis in the general cat population and identify risk factors. The prevalence of feline hemotropic mycoplasmosis was determined to be 4.9 percent in all cats. As might be expected, in healthy cats the prevalence is a bit lower (3.6 percent), while in sick cats, it’s a bit higher (7.5 percent). The true prevalence of the disease may be underestimated because of the difficulty diagnosing the disorder.

Factors identified as increasing the estimated risk for hemotropic mycoplasmosis were:

• Illnesses
• Anemia. A finding of anemia increases the chance of the cat having hemotropic mycoplasmosis
• FeLV status. A positive correlation exists between feline leukemia virus infection and hemotropic mycoplasmosis
• Infrequent vaccination
• A history of cat-bite abscesses
• Age. There is a higher prevalence in cats less than 3 years old.
• Indoor/outdoor status. Free-roaming, outdoor cats are at higher risk.

The mode of transmission in naturally occurring infection has been difficult to elucidate fully. It is believed that hemotropic mycoplasmosis is transmitted by insect vectors, such as fleas, ticks, and mosquitoes, direct contact between cats such as with bite wounds and via blood transfusions. Transmission in utero or by breast milk has been suggested by the detection of the organism soon after birth; intrauterine transmission was suspected when kittens from an infected queen were found to be infected three hours after birth. There are no known risks to humans.

Cats with hemotropic mycoplasmosis experience four phases of disease.

• The pre-parasitemic phase. The first phase lasts from 2 to 21 days; during this phase, cats are infected, but don’t show clinical signs, and the organism is not detectable in the bloodstream.
• The acute phase. The second phase lasts from 2 to 4 months. During this phase, clinical signs occur intermittently, and parasitemia, which is the presence of the organism in the bloodstream, also occur intermittently. Clinical signs vary. Some cats in the acute phase of disease have signs that are so mild that they remain undetected by their owners, while other cats have such severe signs that they may lead to death if left untreated.
• The recovery phase. The third phase can vary in duration. Cats can remain mildly anemic, clinical signs are not apparent, and phases of parasitemia are minimal.
• The carrier phase. The fourth phase can last for years. Cats appear clinically normal and the organism is rarely detectable in the bloodstream.

Clinical signs and physical exam findings of Mycoplasma haemofelis infection are similar to that seen with other anemias; the severity of the clinical symptoms is related to the magnitude of the anemia, and how quickly that degree of anemia was reached. Pale (possibly yellow tinged) mucous membranes, fever, fatigue, depression, tachypnea (rapid respiratory rate), tachycardia (rapid heart rate), decreased appetite, and enlarged liver and spleen are some of the symptoms that may be observed in cats with hemotropic mycoplasmosis.

In-depth Information about Diagnosis of Feline Infectious Anemia

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 (clumping) of the red blood cells and eventually, their destruction. Mycoplasma haemofelis induces these types of antibodies, and a positive Coomb’s test is further evidence of the disorder.
• 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.

In-depth Information about Treatment of Feline Infectious Anemia

• 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 for Feline Infectious Anemia

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.

Home Care for Feline Infectious Anemia

Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve. Administer all prescribed medication as directed and alert your veterinarian if you are experiencing problems treating your pet.

Have your cat re-examined according to a schedule set by your veterinarian, to make sure that the red blood cell count is rising and the anemia is resolving.

The prognosis for recovery is good when hemotropic mycoplasmosis occurs as a primary problem; up to 75 percent survive the episode if a definitive diagnosis is made and therapy is instituted. Even without treatment, about 65 percent of acutely ill cats will survive. Recovered cats become carriers for an unknown duration of time, possibly throughout life. Prior exposure does not induce immunity, and recurrence of disease is theoretically possible, although this rarely happens.

The prognosis is worse if Mycoplasma haemofelis is an opportunist, especially if the primary disorder is FeLV. If the feline leukemia virus has already affected the bone marrow, treatment is usually unrewarding; blood transfusions plus antibiotic therapy does not induce long-term remission.