Feline Infectious Anemia: An Overview
Dog Breeds
Cats can be infected by a tiny red blood cell parasite that was formerly called Hemobartonella felis. This disease, which results from a bacterial infection, is referred to as feline infectious anemia. The infectious agents responsible for the disease have been renamed C. Mycoplasma haemominutum (CMhm) for the small sized strain and Mycoplasma haemofelis for the large sized strains. It is important to make this distinction because these two subtypes of the blood parasite produce quite different clinical signs.
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Definition
Feline infectious anemia (FIA) is a disorder caused by a tiny red blood cell parasite, Mycoplasma haemofelis (and, less frequently, by Mycoplasma haemominutum).
How Feline Infectious Anemia Affects Cats
Infected animals develop a progressive and usually cyclic decrease in the number of healthy circulating red blood cells, which leads to weakness, inappetance, lethargy, depression, splenomegaly, weight loss, pallor, often a fluctuating fever and sometimes sudden death.
Causes of Feline Infectious Anemia
FIA is caused by Mycoplasma haemofelis and, less commonly, by Mycoplasma haemominutum. These are parasitic bacterial microorganisms that attach to the surface membranes of red blood cells, initiating an immune response in the cat as if the affected blood cells were foreign intruders. Naïve cats can become infected through bites by fleas and ticks that have fed on blood from infected cats. Infection is also transmitted through bite wounds, most commonly incurred during territorial squabbles between intact tom cats. Kittens with infected mothers often are infected either transplacentally, through the milk or from ingesting maternal blood somehow during the birth process. Transfusion with infected whole blood or blood products can confer infection as well.
Preventing Feline Infectious Anemia
Cats kept exclusively indoors are much less likely to develop FIA, because they are not exposed to cat fights and uncontrolled feral cat populations. Routine flea and tick control is especially important if cats are allowed to go outdoors or if indoor cats are in contact with other pets with outdoor access (dogs, cats, others). Neutering and spaying can reduce roaming tendencies and decrease the chances of territorial cat fights.
Special Notes
Finding the causative organism microscopically on a blood smear is diagnostic of FIA. However, these organisms are difficult to detect given the cyclic nature of the disease, and serial blood samples may be recommended. Blood work in infected cats will reflect a regenerative anemia. A polymerase chain reaction (PCR) test has been developed to identify the particular causative organisms, but these may not yet be commercially or widely available.
The more pathogenic strain of this organism can cause fatality in up to 30% of untreated cats, making prompt treatment essential. Cats with concurrent viral infections are usually more severely affected, and co-infection unfortunately is rather common in cats with FIA.
Antibiotics, steroid therapy and perhaps intravenous fluids and whole-blood transfusions may be required. Therapy never completely clears the parasite, although relapse is uncommon.
Causes of Feline Infectious Anemia