Haemobartonella felis

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Haemobartonella felis

Characteristics of the symbiont/pathogen

Haemobartonella felis has been recently renamed to Mycoplasma haemofelis due to a closer relation to the genus Mycoplasma rather than the genus Bartonella (10). The genome of Mycoplasma haemofelis has been completely sequenced, and in fact is the first hemotrophic mycoplasma species to be completely sequenced. In a study that compared two strains of the microbe, Ohio2 and Langford 1, they found that the complete genome of the circular chromosome was 1,155,937 base pairs (5). Mycoplasma haemofelis has a large genome that contains a large amount of unique proteins (Figure 1).

The phylogenetic classification of Mycoplasma haemofelis is (4):

Domain: Bacteria

Phylum: Tenericutes

Class: Mollicutes

Family: Mycoplasmataceae

Genus: Mycoplasma

Species: Haemofelis

The cell morphology of Haemobartonella felis, or Mycoplasma haemofelis, is a short coccus- or rod-shaped , gram negative bacteria. It also lacks a cell wall. Because the microbe is unable to be cultured,a microscopic identification from a blood smear is needed for diagnosis (3).

Figure 1. Structure of the genome of Mycoplasma haemofelis[1]

Figure 2. Cell Morphology for Haemobartonella felis [2]

Characteristics of the host

What host/s is/are involved? Is there host specificity? Are there secondary reservoirs?

The host for Mycoplasma haemofelis is a feline. It is unclear of what breeds of felines are most commonly effected. However, it is found that felines of older non-pedigree are more at risk for the infection that Mycoplasma haemofelis even though younger felines can be affected (9). In other studies, they found that the infection is more common in felines from regions like Switzerland and other European countries (11).

Host-Symbiont Interaction

What kind of interaction do host and symbiont have? How is the host affected by the relationship? How does the host acquire and transmit the symbiont? Is the interaction obligate or facultative?

The interaction of the host, a feline, and the symbiont, Mycoplasma haemofelis is one of a parasitic relationship. If the host acquires a relationship with the symbiont, the host will become anemic, which effects the host red blood cell count. It is unclear of how the symbiont and disease is transmitted. However, some studies suggest that it is transmitted by fleas so flea control is suggested for felines. Yet, because it is known that the symbiont causes problem in the host's blood it can be determined that another source of transmission is inoculation of infected blood. One of the symptoms for this disease are pale gums (Figure 3).

Since transmission is unclear, treatments are possible but not known to completely treat anemia for the infected feline. The most commonly used treatment is doxycycline that can be used for 14-21 days with one dosage a day. If the anemic conditions of the host are severe a blood transfusion may be recommended (7).

The interaction is obligate, because the microbe Mycoplasma haemofelis needs the host in order to carry out specific cell functions. The class of Mycoplasma haemofelis, Mollicutes, have been studied and determined to be dependent on hosts or other bacterium for guanine phosphoribosyl-transferase activity in order to carry out purine metabolism (9).

Figure 3. A feline infected by Mycoplasma haemofelisthat has caused pale gums.[3]

Molecular Insights into the Symbiosis

Describe molecular/genetic studies on the symbiosis.

In some recent studies, the species Mycoplasma haemofelis has been compared to two other haemoplasma species, Candidatus M. haemominutum and Candidatus M. turicensis. In comparison of effects on the host of the symbiont, Mycoplasma haemofelis causes haemolysis and Candidatus M. haemominutum does not usually cause anemia. Coombs' tests and blood glucose concentration tests were used to determine the differences between these three species. Coomb's testing was used to determine the presence for erythrocyte-bound antibodies and if the red blood cells become destroyed. The species Mycoplasma haemofelis was the only species that tested positive for Coomb's test. For glucose concentrations, the species Candidatus M. turnicensis had lower concentrations than the other two species as well as lower blood copy numbers. In conclusion of this study, they found that the species Mycoplasma haemofelis was the only to develop macrocytic anemia (6).

Many genes of Mycoplasma haemofelis have been studied. The two genes IMP (inosine-5′-monophosphate) dehydrogenase and GMP (guanosine 3′,5′-monophosphate) synthase have been found to encode proteins and partake in biosynthesis. This is significant because these enzymatic activities of these genes have not been found in Mollicutes. This raises the question if Mycoplasma haemofelis need a host in order to perform guanine biosynthesis. However, there is not enough research completed yet in order to determine this. Yet, it is not clear what are the enzymes activities. In addition, there is a gene that is very unique to Mycoplasmas haemofelis which is the gene superoxide dismutase (SOD), because it is not found or sequenced in other mycoplasmas. This gene may suggest that Mycoplasma haemofelis is actually facultative; however, there is no clear evidence of the genes' activity. Further on in these studies, it is found that this species has many unique proteins and genes. Because of the unique genes, it is understood that this species of mycoplasma has adapted it self colonize the red blood cell rather than mucosal surfaces like most mycoplasmas do and this is why it survives in it's host (2).

Ecological and Evolutionary Aspects

What is the evolutionary history of the interaction? Do particular environmental factors play a role in regulating the symbiosis?

In the past decade or so, this microbe has changed from Haemobartonella to Mycoplasma. This has been reclassified because in studies the microbe has been determined to be more related to Mollicutes than Rickettsiales. In addition, Mycoplasma haemofelis is unculturable which makes it difficult to diagnosis. However, with more recent research on the microbe it is possible to diagnosis for the infection by the polymerase chain reaction rather than the older method of studying the red blood cells which resulted in false positive and false negative due to other factors. These new PCR methods have contributed to the identification of two strains of Mycoplasma haemofelis, Ohio strain and California strain. The difference between these two strains are the presence of anemia in the feline, in which the Ohio strain causes a more severe infection that could result in haemolytic anemia that could be fatal. Since there are strains from different geological regions and most felines affected are found in Europe, this may suggest that environmental factors play a role in regulating the symbiosis. However,Mycoplasma haemofelis is still in the early stages of research for its difficulty in culturing, so as of now environmental factors are not determined(7).

Recent Discoveries

Describe two findings on the symbiosis published within the last two years. Barker (2011), Willi (2010)

References

1. Barker, E.N. et al. (2011). Complete genome sequence of Mycoplasma haemofelis, a Hemotropic Mycoplasma. J. Bacteriol, 193.8, 2060-2061.

2. Berent, L.M., and Messick, J.B. (2003). Physical map and genome sequencing survey of Mycoplasma haemofeli (Haemobartonella felis). American Society of Microbiology, 71.6, 3657-3662.

3. Messick, J.B., Berent, L.M., and Cooper, S.K. (1998).Development and evaluation of PCR-Based assay for detection of Haemobartonella felis in cats and differentiation of H. felis from related bacteria by restriction fragment length polymorphism analysis. Journal of Clinical Microbiology, 36.2, 462-466.

4. Genome information for Mycoplasma haemofelis. NCBI Website.

5. Santos et al. (2011). Genome of Mycoplasma haemofelis, unraveling its strategies for survival and persistence . Veterinary Research, 42.102, 1-16.

6. Tasker, S. et al. (2009). Description of outcomes of experimental infection with feline haemoplasmas: Copy numbers, haematology, Coomb’s testing and blood glucose concentrations. Vet. Microbiol., 139.3-4, 323-332.

7. Tasker, S. and Lappin, MR. (2002). Haemobartonella felis: recent developments in diagnosis and treatment. Journal of Feline Medicine and Surgery, 4, 3-11.

8. Tasker, S. (2010). Haemotropic mycoplasmas: What’s their real significance in cats? J Feline Med Surg., 12.5, 369-381.

9. Tryon,V. and Pollack, D. (1985). Distinctions in Mollicutes Purine Metabolism: Pyrophosphate-Dependent Nucleoside Kinase and Dependence on Guanylate Salvage. International Journal of Systematic Bacteriology, 35.4, 497-501.

10. Willi, B. et al. (2007). From Haemobartonella to hemoplasma: Molecular methods provide new insights. Vet. Microbiology, 125.3-4, 197-209.

11. Willi, B. et al. (2010). Haemotrophic mycoplasmas of cats and dogs: transmission, diagnosis, prevalence and importance in Europe. Schweiz Arch Tierheilkd, 152.5, 237-44.

Edited by Maggie Benson, students of Grace Lim-Fong

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