Introduction

Feline infectious anemia (FIA) is an infection by a bacterial blood parasite that latches onto the surface of feline red blood cells, triggering an auto-immune response which results in reduced numbers of healthy circulating red blood cells. Cats infected by this microorganism may be asymptomatic or may develop a number of acute and chronic signs of anemia ranging from mild to very severe. These signs often are vague and nonspecific, reflecting the existence rather than the cause of the anemia.

Symptoms of Feline Infectious Anemia

Red blood cells, also called erythrocytes, contain a molecule called hemoglobin that is responsible for transporting oxygen throughout the body. A decrease in the amount of red blood cells causes an insufficient amount of oxygen delivery to the brain and other vital tissues. Once a cat is infected, it typically takes about 10 days for clinical signs to develop, if they develop at all. Cycles of parasitemia (detectable levels of parasites in the blood) then occur, lasting 1 to 2 days with an average of 6 days between episodes. The level of parasites in the blood can vary markedly within a matter of hours. Adult cats, especially males, are reportedly more frequently affected, as are free-roaming unvaccinated animals and FeLV-positive cats.

In acute cases, affected animals suddenly become weak, lethargic, depressed, anorexic and pale. They may or may not have a fluctuating fever and bouts of vomiting. Their mucus membranes tend to turn blue-ish, and their heart and respiratory rates become elevated. In extreme cases, FIA can cause sudden death. Cats with chronic clinical disease have similar symptoms, but their signs linger and eventually are accompanied by weight loss, poor body condition, an enlarged spleen and chronic fatigue.

Cats infected with feline leukemia virus have a greater risk of developing severe disease when they also become infected with the microorganism that causes feline infectious anemia. Currently, there is no direct evidence that the strength of a cat’s immune system plays a significant role in whether or not the symptoms of FIA are mild or severe.