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==Introduction==

==Introduction==

Feline Infectious Anaemia is a regenerative anaemia of cats caused by '''''Mycoplasma haemofelis''''' (Mhf). The disease occurs worldwide and should be considered as a differential diagnosis for any cat presenting with anaemia.   

Feline Infectious Anaemia is a [[Regenerative_and_Non-Regenerative_Anaemias|regenerative anaemia]] of cats caused by '''''Mycoplasma haemofelis''''' (Mhf). The disease occurs worldwide and should be considered as a differential diagnosis for any cat presenting with anaemia.   

==Aetiology==

==Aetiology==

Mhf is one of a group of organisms known as haemotropic mycoplasmas which infect many mammalian species. The causative organism was previously called ''Haemobartonella felis'' and thus the disease was known as haemobartonellosis. Polymerase chain reaction (PCR) assays allowing DNA analysis resulted in the reclassification of the organism as a mycoplasma in 2001<ref name="Niemark">Niemark H, Johansson KE, Rikihisa Y, et al (2001) Proposal to transfer some members of the genera ''Haemobartonella'' and ''Eperythrozoon'' to the genus ''Mycoplasma'' with descriptions of Candidatus ''Mycoplasma haemofelis'', Candidatus ''Mycoplasma haemomuris'', Candidatus ''Mycoplasma haemosuis'' and Candidatus ''Mycoplasma wenyonii'' '''Int J Sys Evol Microbiol 51(3) pp891-9</ref>. Two other haemotropic mycoplasmas (''Candidatus M. haemominutum'' (Mhm) and ''Candidatus M. turicensis'' (Mtc)) have also been identified in cats but appear to be less pathogenic<ref name="Sykes">Sykes, JE (2010) Feline Hemotropic Mycoplasmas '''Vet Clinics of North America: Small Animal Practice''' pp. 1157-1170</ref>.

Mhf is one of a group of organisms known as haemotropic [[Mycoplasmas|mycoplasmas]] which infect many mammalian species. The causative organism was previously called ''Haemobartonella felis'' and thus the disease was known as haemobartonellosis. [[Polymerase_Chain_Reaction|Polymerase chain reaction]] (PCR) assays allowing DNA analysis resulted in the reclassification of the organism as a mycoplasma in 2001<ref name="Niemark">Niemark H, Johansson KE, Rikihisa Y, et al (2001) Proposal to transfer some members of the genera ''Haemobartonella'' and ''Eperythrozoon'' to the genus ''Mycoplasma'' with descriptions of Candidatus ''Mycoplasma haemofelis'', Candidatus ''Mycoplasma haemomuris'', Candidatus ''Mycoplasma haemosuis'' and Candidatus ''Mycoplasma wenyonii'' '''Int J Sys Evol Microbiol 51(3) pp891-9</ref>. Two other haemotropic mycoplasmas (''Candidatus M. haemominutum'' (Mhm) and ''Candidatus M. turicensis'' (Mtc)) have also been identified in cats but appear to be less pathogenic<ref name="Sykes">Sykes, JE (2010) Feline Hemotropic Mycoplasmas '''Vet Clinics of North America: Small Animal Practice''' pp. 1157-1170</ref>.

Mhf can vary in shape from cocci to rods and is sometimes present as chains of organisms on the cell surface.

Mhf can vary in shape from cocci to rods and is sometimes present as chains of organisms on the surface of [[Erythrocyte|erythrocytes]].

==Transmission==

==Transmission==

The mode of transmission of Mhf is poorly understood. Several possibilities have been proposed but none have been able to be reliably demonstrated. These include:

The mode of transmission of Mhf is poorly understood. Several possibilities have been proposed but none have been able to be reliably demonstrated. These include:

* Biting and fighting activities. Infection by this route has not been able to be demonstrated experimentally.  

* Biting and fighting activities. Infection by this route has not been able to be demonstrated experimentally.  

*Fleas. The fact that Mhf infection can be prevalent in areas where fleas are uncommon makes this less likely<ref name="Jensen"> Jensen WA, Lappin MR, Kamkar S et al (2001) Use of a polymerase chain reaction assay to detect and differentiate two strains of ''Haemobartonella felis'' in naturally infected cats. '''Am J Vet Res''' 62(4):604-8 </ref>

*[[Fleas|Fleas]]. The fact that Mhf infection can be prevalent in areas where fleas are uncommon makes this less likely<ref name="Jensen"> Jensen WA, Lappin MR, Kamkar S et al (2001) Use of a polymerase chain reaction assay to detect and differentiate two strains of ''Haemobartonella felis'' in naturally infected cats. '''Am J Vet Res''' 62(4):604-8 </ref>

*Arthropods. Geographic variation in rates of Mhf infection does exist and could be due to transmission by an arthropod <ref name="Willi">Willi B, Boretti FS, Baumgartner C et al (2006) Prevalence, risk factor analysis and follow-up of infections caused by three feline haemoplasma species in Switzerland. '''J Clin Microbiol''' 44(3):961-9</ref>.

*[[Arthropods|Arthropods]]. Geographic variation in rates of Mhf infection does exist and could be due to transmission by an arthropod <ref name="Willi">Willi B, Boretti FS, Baumgartner C et al (2006) Prevalence, risk factor analysis and follow-up of infections caused by three feline haemoplasma species in Switzerland. '''J Clin Microbiol''' 44(3):961-9</ref>.

==Signalment==

==Signalment==

The major group at risk for Mhf infection are young male cats who spend time outdoors. In many areas of the world an association has been shown between Mhf and retroviral infections<ref name="Sykes"></ref>. It has been demonstrated that cats infected with Mhf and feline leukaemia virus (FeLV) are likely to develop more severe anaemia that cats infected only with Mhf <ref name="Wardrop"></ref>.  

The major group at risk for Mhf infection are young male cats who spend time outdoors. In many areas of the world an association has been shown between Mhf and [[Retroviridae|retroviral infections]]<ref name="Sykes"></ref>. It has been demonstrated that cats infected with Mhf and [[Feline_Leukaemia_Virus|feline leukaemia virus (FeLV)]] are likely to develop more severe anaemia that cats infected only with Mhf <ref name="Wardrop"></ref>.  

==Pathogenesis==

==Pathogenesis==

The pathogenesis of Mhf is not fully understood. It is thought that the presence of the parasite on the surface of the red blood cells may induce antibody production<ref name="Hagiwara"></ref>. The anaemia, which is primarily extravascular, may be due to direct damage of erythrocytes by the organism or as a result of the antibodies produced by the infected animal <ref name="Wardrop"></ref>.

The pathogenesis of Mhf is not fully understood. It is thought that the presence of the parasite on the surface of the erythrocytes may induce [[Immunoglobulins_-_Overview|antibody production]]<ref name="Hagiwara"></ref>, resulting in[[Regenerative_and_Non-Regenerative_Anaemias#Haemolysis|haemolysis]] which is primarily extravascular. The haemolysis may be due to direct damage of erythrocytes by the organism or as a result of the antibodies produced by the infected animal <ref name="Wardrop"></ref>.

Cats can produce an immune response which results in the disappearance of organisms from the blood. Production of uninfected erythrocytes  can then result in an increase in haematocrit.  

Cats can produce an immune response which results in the disappearance of organisms from the blood. Production of uninfected erythrocytes  can then result in an increase in haematocrit.