Mycoplasma haemofelis

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A Microbial Biorealm page on the genus Mycoplasma haemofelis


Higher order taxa

Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma


NCBI: Taxonomy

Mycoplasma Haemofelis

Description and significance

Mycoplasma haemofelis was previously known as Eperythrozoon felis or Haemobartonella felis, and it was recognized as rickettsiae until the late 90’s (1). However, as more and more researches were done on this specific bacteria, researchers realized that the classification for the bacteria had to be changed. These bacteria were parasitic, contained flagella, had small genome, and most importantly, the lack of cell wall. Therefore, researchers moved the bacteria to the class Mollicutes and the genus Mycoplasma (7). Mycoplasma haemofelis was first discovered by Flint and Moss in the United States in 1953, and they first described these bacteria as pathogens of the felines.

Mycoplasma haemofelis is a parasite that resides on the surface of red blood cell on felines, and it is about 0.5 um in diameter (1). In blood smears, the bacteria may be shaped as rings, rods or circles; sometimes they cluster together and form chains of bacteria on the surface of red blood cell (7). Further, there are three hemotropic Mycoplasmas that can infect felines: Mycoplasma haemofelis, Candidatus Mycoplasma haemominutum, and Candidatus Mycoplasma turicensis. As researches have shown, multiple infections of the above pathogens will increase the severity of the clinical signs of Mycoplasma haemofelis infection (3). The prevalence of the bacteria has been estimated among domestic cats, and the infection rate appears to be 4.9 to 23.3 %; yet the actual prevalence in not calculated because the infections are not always detectable. Common diseases caused by Mycoplasma haemofelis are feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), and feline infectious peritonitis, and most importantly, feline infectious anemia (FIA) (1, 5). However, due to several metabolism pathways, the bacteria are hard to cultivate in labs, and they often contaminate other eukaryotic cultures (6). Details will be explained in the [Cell structure and Metabolism] section down below.

Genome structure

Mycoplasma haemofelis’ linear chromosome has an average of 1,199 kb with the standard deviation of 13.5 kb. The size fits well in the range or 580 to 1,400 kb for the genus Mycoplasma. 75 new genes were identified by running the sample with random sequencing, and these genes had never been reported or discovered for Mycoplasma haemofelis or other mycoplasma. Like all mycoplasma, which have a G+C (guanine-cytosine) percentage of below 50 %, Mycoplasma haemofelis has a G+C percentage of 38.5 % (2). One special feature of these bacteria is that the UGA codon is used for tryptophan instead of being a stop codon (6). Escherichia coli strain DH10B and the vector pBeloBAC11 can be used to create the bacterial artificial chromosome (BAC) library for Mycoplasma haemofelis. 430 never-before-seen genome survey sequences (GSS) were discovered by studying the BAC, and these sequences have now been added to the database of GenBank (2).

Mycoplasma haemofelis is unique compare to other mycoplasmas, and one of the reasons is that these bacteria contain the superoxide dismutase (SOD) gene while others do not. However, the SOD gene has not been fully studied and sequenced. Two other genes in particular interest many researchers because the enzyme activities of these genes were largely unknown in Mycoplasma haemofelis. One of the gene is related to purine biosynthesis, and the other one encode proteins that are closely related to inosine-5’-monophosphate dehydrogenase and guanosine-3’, 5’-monophosphate synthase (2).

Cell structure and metabolism

Mycoplasma haemofelis have filaments with special polar tips that help the bacteria attach to the hosts. These tips were formed by complex network of protein, designated adhesins, and adherence-accessory proteins. It is because of this tips that the bacteria are able to colonize on the surface eukaryotic cells (6).

Because of the small genome, Mycoplasma haemofelis is completely dependent on the host for nutrients and survival. With no cell wall components, Mycoplasma haemofelis has a unique plasma membrane that contains sterol, and the bacteria obtain the sterol from the host in the form of cholesterol. Further, Mycoplasma haemofelis must acquire most of the biosynthetic precursors from the host, for example, nucleotides, amino acids, cholesterol, and fatty acids. Consequently, this pathogen is hard to cultivate in a lab setting because of the bacteria’s highly demand for hosts, and yet it remain as one of the top contamination to other eukaryotic cells and tissue cultures (6). On the other hand, by being a parasite on the surface of red blood cell, Mycoplasma haemofelis can obtain the most nutrients from the host and grow in to large colonies. As studies have shown, although the bacteria are cell surface parasites, they do not penetrate the cell (7).




As mentioned before, Mycoplasma haemofelis is a feline parasite, and it can cause several diseases, such as, feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), feline infectious peritonitis, and feline infectious anemia (FIA). General symptoms of infected felines includes anorexia, depression, lethargy, weakness, intermittent fever (40-42oC), weight loss, and in the end, death (1). The fever cycles because the number of bacteria varies, and the fever gets worse as the number of parasite increases in the peripheral blood. More symptoms will show up as the infection gets more sever and the bacteria may become regenerative. These symptoms include splenomegaly, icterus, anisocytosis, polychromasia, increase of reticulocytes or immune-mediated hemolytic anemia (1, 7).

Mycoplasma haemofelis can be transmitted vertically and horizontally. In vertical transmission, the kitten can be infected in the uterus, via parturition or nursing from the milk. On the other hand, what is known for horizontal transmission is that cats can get infected through infected blood or needles. The diagnosis of the parasites involves the careful studying of complete blood counts and peripheral blood smears. However, infection can go undetected if the sample is not obtained during parasitemic phase (1).

There are several possible treatments for Mycoplasma haemofelis, and some of them do perform a better job than others. Even though the bacteria react with the antibiotic tetracycline, this antibiotic has to be taken frequently and it may cause fever. On the other hand, by blocking protein synthesis, the antibiotic doxycycline does work better and is the preferred drug. Yet, side effect such as abdominal discomfort, esophagitis or anorexia may occur when the felines took doxycycline. Another possible drug is enrofloxacin, which only have to be taken once a day and have fewer side effects than doxycycline. Unfortunately, none of the drugs/antibiotics tested were able to completely eliminate the parasite, and all these drugs are capable of is control the infection (7).

Application to Biotechnology

Due to the nature of Mycoplasma haemofelis, it is very hard to cultivate this specific parasite or grow them into large quantities. Most of the researches have to collect the sample from infected felines instead of grown cultures. Hence, there is no current application of Mycoplasma haemofelis to biotechnology yet (1, 2, 5).

Current Research




Edited by student of Rachel Larsen