ISSN 2398-2950      

Feline infectious anemia


Synonym(s): FIA, hemotrophic mycoplasmosis, hemobartonellosis


  • Cause: hemotropic bacteria known as hemoplasmas (Mycoplasma haemofelisCandidatus Mycoplasma haemominutum, 'Candidatus Mycoplasma turicensis'). The protozoal parasite (Babesia felis) causes similar disease in some parts of the world (eg South Africa).
  • Signs: changes consistent with immune-mediated hemolytic anemia (eg lethargy, inappetence, depression, pallor, tachycardia, tachypnea) and inflammation (fever).
  • Diagnosis: hematology plus PCR confirmation of organisms (ideal) or demonstration of intracellular parasites on blood smear (less ideal).
  • Treatment: antimicrobials - doxycycline or fluoroquinolones (eg marbofloxacin, pradofloxacin).
  • Prognosis: good unless immunosuppressed.
    Print off the owner factsheet on Feline Infectious Anemia (FIA) Feline Infectious Anemia (FIA) to give to your client.


  • Hemoplasmas (the generic name for the hemotropic mycoplasmas) were re-classified into the genus Mycoplasma from order Rickettsiales genera Haemobartonella and Eperythrozoon based on DNA sequence data. In cats, the more pathogenic large form of Haemobartonella felis (also known as Ohio / Florida / Illinois / Oklahoma variant) was reclassified as M. haemofelis, and the less pathogenic small form of Haemobartonella felis (also known as California / Birmingham variant) was reclassified as ‘Candidatus M. haemominutum’.
  • They are uncultivatable, wall-less (hence Gram-stain negative), obligate parasites of the mammalian red blood cell (RBC). During acute infection they can result in direct or indirect damage to RBC leading to anemia. Presence of a chronic hemoplasma carrier state (particularly with ‘Candidatus M. haemominutum’) has limited association of risk factors with clinical signs of anemia.




  • Common natural route of transmission undetermined.
  • Horizontal transmission through aggressive interactions (bites) suspected, but experimental studies using subcutaneous inoculation of saliva or blood from infected cats showed limited success at transmitting infection.
  • Cat fleas, Ctenocephalides felis Ctenocephalides felis, are suspected play a role, at least in some cases, but experimental studies have not provided strong support that this is a common route.
  • Ticks are thought to provide a common route of hemoplasmas transmission in dogs, and feline hemoplasmas have been detected in ticks; however, experimental studies into the role of ticks in the transmission of hemoplasmas in cats have not been performed.
  • Blood transfusion Blood transfusion of infected blood is an iatrogenic route of transmission.
  • Vertical transmission suggested in early reports, and for other host species.

Predisposing factors


  • There is conflicting evidence on the importance of these factors.
  • May affect cats with some degree of immune compromise:
    • Stress (pregnancy, neoplasia, concurrent infection).
    • Immunosuppression, eg FeLV, FIV,  immunosuppressive drugs.
    • Splenectomy (clinically less important than in dog).
    • May be primary pathogen in some cases.


  • Infection with wall-less (Gram stain-negative) bacteria of different pathogenicities:
    • M. haemofelis is most pathogenic.
    • Candidatus M. haemominutum’ rarely causes clinical disease in the absence of comorbidities.
    • Candidatus M. turicensis’ appears to be of intermediate pathogenicity, but generally clinical disease is uncommon.
  • Hemoplasmas parasitize the surface of RBC → shorter RBC lifespan (hemolysis or splenic sequestration) → anemia:
    • RBC membrane damaged at site of hemoplasma binding.
    • Bystander damage.
  • Antibodies against the RBCs may be induced leading to immune-mediated hemolysis as evidenced by auto-agglutination or a positive Coombs test result (but these are detectable after the onset of anemia).
  • Clearance of parasite can occur in the spleen without loss of red cell, allowing cells to return to the circulation. This may explain the rapid recovery from clinical signs and increase the PCV following treatment, sometimes without evidence of reticulocytosis.
  • Acute M. haemofelis infection can result in cyclical changes in hematocrit in some cats.


  • In experimental studies hemoplasmas can be detected from 2 days post-inoculation with anemia typically occurring from two weeks post-inoculation (but can be much shorter at 5 days).
  • Animals may be chronically infected (carrier state).
  • Relapse of infection (as evidenced by increased hemoplasma numbers and decreased hematocrit) may occur in times of stress or treatment with immunosuppressive agents (eg methylprednisolone acetate), but this typically does not result in clinical signs.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Novacco M, Sugiarto S, Willi B et al (2018) Consecutive antibiotic treatment with doxycycline and marbofloxacin clears bacteremia in Mycoplasma haemofelis-infected cats. Vet Microbiol 217, 112-20 PubMed.
  • Tasker S, Hofmann-Lehmann R, Belák S et al (2018) Haemoplasmosis in cats: European guidelines from the ABCD on prevention and management. J Feline Med Surg 20 (3), 256-61 PubMed.
  • Baumann J, Novacco M, Willi B et al (2015) Lack of cross-protection against Mycoplasma haemofelis infection and signs of enhancement in “Candidatus Mycoplasma turicensis”-recovered cats. Vet Res 46, 104 PubMed.
  • Hicks C A, Willi B, Riond B et al (2015) Protective Immunity against Infection with Mycoplasma haemofelis. Clin Vaccine Immunol 22 (1), 108-118 PubMed.
  • Dowers K L, Tasker S, Radecki SV et al (2009) Use of pradofloxacin to treat experimentally induced Mycoplasma haemofelis infection in cats. Am J Vet Res 70 (1), 105-111 PubMed.
  • Museux K, Boretti F S, Willi B et al (2009) In vivo transmission studies of 'Candidatus Mycoplasma turicensis' in the domestic cat. Vet Res 40 (5), 45 PubMed.
  • Dean R S, Helps C R, Gruffydd-Jones T J et al (2008) Use of real-time PCR to detect Mycoplasma haemofelis and Candidatus Mycoplasma haemominutum in the saliva and salivary glands of haemoplasma-infected cats. J Feline Med Surg 10 (4), 413-417 PubMed.
  • Peters I R, Helps C R, Willi B et al (2008) The prevalence of three species of feline haemoplasmas in samples submitted to a diagnostics service as determined by three novel real-time duplex PCR assays. Vet Microbiol 126 (1-3), 142-150 PubMed.
  • dos Santos A P, dos Santos R P, Biondo A W et al (2008) Hemoplasma infection in HIV-positive patient, Brazil. Emerg Infect Dis 14 (12), 1922-1924 PubMed.
  • Tasker S, Caney S M, Day M J et al (2006) Effect of chronic FIV infection and efficacy of marbofloxacin treatment on Mycoplasma haemominutum infection. Microbes and Infection 117 (2-4), 169-79 PubMed.
  • Woods J E, Wisnewski N, Lappin M R (2006) Attempted transmission of 'Candidatus Mycoplasma haemominutum' and Mycoplasma haemofelis by feeding cats infected Ctenocephalides felis. Am J Vet Res 67 (3), 494-497 PubMed.
  • Willi B, Boretti F S, Cattori V et al (2005) Identification, molecular characterisation and experimental transmission of a new haemoplasma isolate from a cat with haemolytic anemia in Switzerland. J Clin Microbiol 43 (6), 2581-2585 PubMed.
  • Foley J E, & Pedersen N C (2001) Candidatus Mycoplasma haemominutum, a low-virulence epierythrocytic parasite of cats. Int J Syst Evol Microbiol​ 51 (Pt 3), 815-817 PubMed.

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