Immune medicated hemolytic anemia (IMHA) is the new name for Auto Immune Hemolytic Anemia (AIHA) a condition where the feline autoimmune system attacks red blood cells. The Immune System treats the red blood cells as foreign bodies; sending out antibodies which coat the red blood cells with a protein substance to single them out of the blood circulation pool for destruction. This process is called extravascular hemolysis. At the same time, the bilirubin (iron) that is extracted from these marked blood cells are sent to the liver. When this process occurs, the liver and spleen begin having problems. The spleen is overworked by having to process damaged red blood cells and enlarges as result. The liver is overloaded with bilirubin causing jaundice.
When this process is going on, a secondary process is activated called the complement system. Again when the proteins are coated with antibodies (intravascular hemolysis) they too will damage red blood cells. Ultimately the body is left with a low supply of red blood cells. Red blood cells are necessary to carry oxygen to tissues. These erythrocytes are incapable of removing blood gas waste, another important cellular function.
Auto Immune Hemolytic Anemia (AIHA) or Immune Mediated Hemolytic Anemia (IMHA) is a life threatening disease.
What can trigger Immune Mediated Hemolytic Anemia (IMHA)?
A parasite called Hemobartonella Felis and Feline Leukemia Virus infection are the known causes that trigger this disease in cats, there are other reasons associated with dogs.
It is important to take your cat to the veterinarian the moment you see the following signs: the colour of urine is different than normal, dark orange or even brown urine, yellowish or pale gums and yellow in the sclera (whites of the eyes). When your cat has lost its appetite and appears to be weak and listless. You may also notice a slight fever.
A starting point for screening for Auto Immune Hemolytic Anemia is a simple blood test called a Packed Cell Volume Test. The Veterinarian takes a sample of blood and spins it in the vial to separate the blood from the serum. By referring to a chart he can then tell if the red blood cell count is lower than normal. A visual inspection of the actual serum reveals the presence of anemia as well. Normal blood serum is off white but when hemolytic anemia is present it then takes on a bright orange color.
A Hematocrit is essentially the same kind of test but instead of being done in your veterinarian's office, it has to be sent to a laboratory for testing. It too measures the red blood cell count. A cat's blood cell count should be between 29 - 50. Once the cat is found to be anemic from the pre testing, it is then necessary to determine what is causing it. Anemia refers to the lower than normal red blood cell count, but Auto Immune Hemolytic Anemia (AIHA) is the destruction of red blood cells and a life threatening illness.
A CBC is a complete blood count analysis it includes, the size, shape and maturity of red blood cells as well as white blood cell information.
A Combs Test will directly check the presence of antibody coating on the cell. It is the standard used to identify Immune Mediated Hemolytic Anemia (IMHA) from other types of anemia or infectious diseases. However the test can reveal false positive or false negative results.
Radiographs are used to check for tumors.
Treatment and Therapy
To bring up the red blood cell count, cats often require transfusions of whole blood. But when whole blood is not immediately available from a suitable donor, doctors often use artificial blood. However, this blood does not raise the immune system and is eliminated from the body within 48 hours. Artificial blood therefore is used as a temporary measure.
Steroid drugs known as corticosteroids are used to suppress the immune system from producing antibodies. These medications sometimes are the only treatment prescribed for your cat.
Auto Immune Hemolytic Anemia (AIHA) is a very serious disease that should not be treated lightly. It takes extensive testing to determine if your cat has this disease but you can help by watching for the above mentioned symptoms then getting your cat immediate medical attention.