Mycoplasma haemofelis

Mycoplasma haemofelis (formerly Haemobartonella felis) is a gram negative epierythrocytic parasitic bacterium. It often appears in bloodsmears as small (0.6μm) coccoid bodies, sometimes forming short chains of 3 to 8 organisms. It is usually the causative agent of Feline Infectious Anemia (FIA) in the United States. The ~1.15 Mb genome contains a minimalistic assortment of genes limited to the most basic cellular functions. This leaves M. haemofelis inextricably dependent upon its host for the provision of amino acids, cholesterol, vitamins, and fatty acids. The complex and specific conditions the bacterium requires have made it impossible to culture outside a host thus far. Arthropod vectors are thought to be the primary source of infection, although M. haemofelis is also known to be transmitted from queen to kitten and following blood transfusion. Immunocompromization and/or coinfection with FeLV, FIV, and other Mycoplasma species can exacerbate symptoms or cause symptoms to arise in previously asymptomatic individuals. Symptoms include anemia, lethargy, fever, and anorexia. In suspected cases, M. haemofelis can be identified by polymerase chain reaction analysis for species-specific 16S rRNA sequences as well as by light microscopy. Treatment usually includes the administration of doxycycline or enrofloxacin to quell the infection along with transfusion and administration of glucocorticoids to alleviate anemia. Recent evidence suggests that M. haemofelis may be transmissible to humans. M. haemofelis belongs to the phylogenetically diverse class Mollicutes, which comprises 8 genera: Ureaplasma, Spiroplasma, Asteroleplasma, Mesoplasma, Entomoplasma, Acholeplasma, Anaeroplasma, and Mycoplasma. Haemoplasmas is the name given to the trivial cluster that includes M. haemofelis and its close relatives. Before the advent of modern PCR techniques, M. haemofelis and closely related Haemoplasmas Candidatus Mycoplasma haemominutum and Ca. Mycoplasma turicensis were collectively classified as Haemobartonella felis based on similarities in gross morphology. The Candidatus distinction is given to newly described species in which additional evidence is required to support their classification. The inability of researchers to culture many Mycoplasma spp. in vitro has made classification difficult. PCR analysis of 16S rRNA sequences of Haemobartonella spp. showed greater similarity to those of Mollicutes than to those of the family Anaplasmataceae in the order Rickettsiales to which they were previously thought to belong. PCR-based assays have provided evidence that the Ohio variant and California variant of H. felis are in fact distinct species, M. haemofelis and Ca. Mycoplasma haemominutum respectively. A third Haemoplasma, Mycoplasma turicensis, was later identified in domestic cats. Haemoplasma species have also been identified in dogs (M. haemocanis), mice (M. haemomuris), opossum (Ca. M. haemodidelphis), and alpaca (Ca. M. haemolamae). In cats, M. haemofelis is the most virulent Haemoplasma species and is most often implicated in FIA in the United States.