|Class:||Spirochaetes Cavalier-Smith 2002|
|Order:||Spirochaetales Buchanan 1917|
|Family:||Spirochaetaceae Swellengrebel 1907|
|Genus:||Borrelia Swellengrebel 1907|
Borrelia is a genus of bacteria of the spirochete phylum. It causes borreliosis, a zoonotic, vector-borne disease transmitted primarily by ticks and some by lice, depending on the species. There are 36 known species of Borrelia. The genus was named after the French biologist Amédée Borrel.
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)  and National Center for Biotechnology Information (NCBI) and the phylogeny is based on 16S rRNA-based LTP release 111 by 'The All-Species Living Tree' Project 
♦ Type strain lost or not available
♠ Strains found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LSPN)
♥ Strains not lodged at National Center for Biotechnology Information (NCBI) or listed in the List of Prokaryotic names with Standing in Nomenclature (LPSN)
Lyme disease 
Of the 36 known species of Borrelia, 12 of these species are known to cause Lyme disease or borreliosis and are transmitted by ticks. The major Borrelia species causing Lyme disease are Borrelia burgdorferi, Borrelia afzelii, and Borrelia garinii.
Relapsing fever 
Relapsing fever borreliosis often occurs with severe bacteremia. Borrelia recurrentis is transmitted by the human body louse; no other animal reservoir of B. recurrentis is known. Lice that feed on infected humans acquire the Borrelia organisms that then multiply in the gut of the louse. When an infected louse feeds on an uninfected human, the organism gains access when the victim crushes the louse or scratches the area where the louse is feeding. B. recurrentis infects the person via mucous membranes and then invades the bloodstream.
Other tick-borne relapsing infections are acquired from other species, such as Borrelia hermsii or Borrelia parkeri or Borrelia miyamotoi, which can be spread from rodents, and serve as a reservoir for the infection, via a tick vector. Borrelia hermsii and Borrelia recurrentis cause very similar diseases, although the disease associated with Borrelia hermsii has more relapses and is responsible for more fatalities, while the disease caused by B. recurrentis has longer febrile and afebrile intervals and a longer incubation period.
- Immunoflourascent or confirm by serology by observing the organism in blood of patient.
All members of the Borrelia genus that have been examined harbor a linear chromosome that is about 900 kbp in length as well as a plethora of both linear and circular plasmids in the 5-220 kbp size range. Genome sequences have been determined for B. burgdorferi, B. garinii, B. afzelii, B. duttonii and B. recurrentis. The chromosomes, which carry the vast majority of the housekeeping genes, appear to be very constant in gene content and organization across the genus. The content of the plasmids, which carry most of the genes that encode the differentially expressed surface proteins that interact with Borrelia's arthropod and vertebrate hosts, are much more variable. B. burgdorferi strain B31, the B. burgdorferi type strain, has been studied in the most detail and harbors twelve linear and nine circular plasmids that comprise about 612 kbp. The plasmids are unusual, as compared to most bacterial plasmids, in that they contain many paralogous sequences, a large number of pseudogenes and, in some cases, essential genes. In addition, a number of the plasmids have features suggesting that they are prophages. Some correlations between genome content and pathogenicity have been deduced and comparative whole genome analyses promise future progress in this arena.
- Samuels DS; Radolf, JD (editors) (2010). Borrelia: Molecular Biology, Host Interaction and Pathogenesis. Caister Academic Press. ISBN 978-1-904455-58-5.
- J.P. Euzéby. "Borrelia". List of Prokaryotic names with Standing in Nomenclature (LPSN) . Retrieved 2013-03-20.
- Sayers et al. "Borrelia". National Center for Biotechnology Information (NCBI) taxonomy database . Retrieved 2013-03-20.
- 'The All-Species Living Tree' Project."16S rRNA-based LTP release 111 (full tree)". Silva Comprehensive Ribosomal RNA Database . Retrieved 2013-03-20.
- Guo, B.P.; Teneberg, S; Münch, R; Terunuma, D; Hatano, K; Matsuoka, K; Angström, J; Borén, T et al. (2009). "Relapsing fever Borrelia binds to neolacto glycans and mediates rosetting of human erythrocytes". PNAS 106 (46): 19280–19285. doi:10.1073/pnas.0905470106. PMC 2771742. PMID 19884498.
- McNeil, Donald (19 September 2011). "New Tick-Borne Disease Is Discovered". The New York Times. pp. D6. Retrieved 20 September 2011.
- Borrelia genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
- Borrelia Microbe Wiki Page
- NCBI Borrelia Taxonomy Browser
- Walid MS, Ajjan M, Patel N: Borreliosis And Human Granulocytic Anaplasmosis Coinfection With Positive Rheumatoid Factor And Monospot Test: Case-Report. The Internet Journal of Infectious Diseases. 2007; Volume 6, Number 1.