Feline infectious anemia (FIA) is a disease caused by a few hemotrophic mycoplasmas (hemoplasmas), which include Mycoplasma haemofelis (formerly Haemobartonella felis), candidatus Mycoplasma haemominutum, and candidatus Mycoplasma turicensis. The infectious organisms are wall-less microorganisms that attach to the outside of erythrocytes (red blood cells). They many appear round, or as thin rods (short chains), or as rings on blood smears, but they are seen only approximately 50% of the time. Infection may not be detected on blood smears because parasitemia is cyclical and organisms may become detached from RBCs in stored (EDTA) blood samples. Also, the organisms may be difficult to differentiate from stain precipitate.
Severity of disease is variable, ranging from mild anemia with no clinical signs to severe anemia and lethargy. This variability is related to host immune status, the specific infecting organism, concurrent diseases, and whether the infection is acute or chronic. Clinical signs will primarily vary with the rate and severity of anemia. Acute infections can affect cats of all ages, although young cats may be more likely to show clinical illness. PCR tests can detect the organisms and can be used as confirmation of clinical suspicion of FIA. Antimicrobial therapy reduces or eliminates visible parasitemia, but it does not usually clear the infection. Doxycycline, enrofloxacin, and marbofloxacin have been shown to reduce clinical signs of disease. Glucocorticoids may also be given to cats with severe anemia to decrease erythrophagocytosis, but this is controversial because of immunosuppressive potential. Treated cats that recover remain carriers but are not likely to relapse. Hemoplasmas may be transmitted by infected blood or blood-sucking arthropods.
Read more about Hemotropic Mycoplasmas and Blood Parasites of Cats in The Manuals.
References
Novacco M, Sugiarto S, Willi B, et al. Consecutive antibiotic treatment with doxycycline and marbofloxacin clears bacteremia in Mycoplasma haemofelis-infected cats. Vet Microbiol. 2018 Apr;217:112-120. doi: 10.1016/j.vetmic.2018.03.006.
Riemer F, Kuehner KA, Ritz S2, Sauter-Louis C, Hartmann K. Clinical and laboratory features of cats with feline infectious peritonitis--a retrospective study of 231 confirmed cases (2000-2010). J Feline Med Surg. 2016 Apr;18(4):348-56. doi: 10.1177/1098612X15586209.
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