''Borrelia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

of the

spirochete A spirochaete () or spirochete is a member of the phylum Spirochaetota (), (synonym Spirochaetes) which contains distinctive diderm (double-membrane) gram-negative bacteria, most of which have long, helically coiled (corkscrew-shaped or s ...

phylum. Several species cause

Lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the '' Borrelia'' bacterium, which is spread by ticks in the genus '' Ixodes''. The most common sign of infection is an expanding red rash, known as erythema ...

, also called Lyme borreliosis, a

zoonotic A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that has jumped from a non-human (usually a vertebrate) to a human. ...

, vector-borne disease transmitted by

ticks Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...

. Other species of ''Borrelia'' cause

relapsing fever Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus '' Borrelia'', which is transmitted through the bites of lice or soft-bodied ticks (genus '' Ornithodoros''). Signs and symptoms Most people who a ...

, and are transmitted by ticks or

lice Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a resul ...

, depending on the species of bacteria. A few ''Borrelia'' species as ''Candidatus'' Borrelia mahuryensis harbor intermediate genetic features between Lyme disease and relapsing fever ''Borrelia''. The genus is named after French biologist Amédée Borrel (1867–1936), who first documented the distinction between a species of ''Borrelia'', ''B. anserina'', and the other known type of spirochete at the time, ''

Treponema pallidum ''Treponema pallidum'', formerly known as ''Spirochaeta pallida'', is a spirochaete bacterium with various subspecies that cause the diseases syphilis, bejel (also known as endemic syphilis), and yaws. It is transmitted only among humans. It ...

''. This bacterium must be viewed using dark-field microscopy, which make the cells appear white against a dark background. ''Borrelia'' species are grown in Barbour-Stoenner-Kelly medium. Of 52 known species of ''Borrelia'', 20 are members of the Lyme disease group (with an additional 3 proposed), 29 belong to the relapsing fever group, and two are members of a genetically distinct third group typically found in reptiles. A proposal has been made to split the Lyme disease group based on genetic diversity and move them to their own genus, ''Borelliella'', but this change is not widely accepted. This bacterium uses hard and soft ticks and lice as vectors. Testing for the presence of the bacteria in a human includes two-tiered serological testing, including immunoassays and immunoblotting.

Biology

''Borrelia'' species are members of the family Spirochaetaceae, so present the characteristic

(spiral) shape. Most species are obligate anaerobes, although some are aerotolerant. ''Borrelia'' species have an outer membrane that contains a substance similar to lipopolysaccharides, an inner membrane, and a layer of peptidoglycan in a periplasmic space, which classifies them as Gram-negative. However, this result is not easily visualized using

Gram staining In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish ba ...

. They are typically 20–30 μm long and 0.2–0.3 μm wide. Spirochetes move using axial filaments called endoflagella in their periplasmic space. The filaments rotate in this space, between the outer membrane and the peptidoglycan layer, propelling the bacterium forward in a corkscrew-like motion. The outer membrane of ''Borrelia'' species contains outer surface proteins (Osp) that play a role in their virulence.

Phylogeny

The currently accepted taxonomy is based on the

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical ...

(LPSN) and

National Center for Biotechnology Information The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. T ...

(NCBI). Notes:
♦ Type strain lost or not available Unassigned species: * "''Ca.''

Borrelia africana ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

" Ehounoud et al. 2016 * "''Ca.'' Borrelia algerica" Fotso et al. 2015 * "''Ca.''

Borrelia aligera ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" Norte et al. 2020 * ''

Borrelia baltazardii ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

'' corrig. Karimi et al. 1979 ex Karimi et al. 1983 * ''

Borrelia brasiliensis ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

'' ♦ Davis 1952 * ''

Borrelia caucasica ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

'' ♦ (Kandelaki 1945) Davis 1957 * ''

Borrelia dugesii ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

'' ♦ (Mazzotti 1949) Davis 1957 * "''Ca.''

Borrelia fainii ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" Qiu et al. 2019 * ''

Borrelia graingeri ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

'' ♦ (Heisch 1953) Davis 1957 * ''

Borrelia harveyi ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

'' ♦ (Garnham 1947) Davis 1948 * "''Ca.''

Borrelia ibitipocensis ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" corrig. Muñoz-Leal et al. 2020 * "''Ca.''

Borrelia ivorensis ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" Ehounoud et al. 2016 * "''Ca.''

Borrelia javanense ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" Jiang et al. 2021 * "''Ca.''

Borrelia johnsonii ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" Schwan et al. 2009 * "''Ca.''

Borrelia kalaharica ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" Fingerle et al. 2016 * ''

Borrelia latyschewii ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

'' ♦ (Sofiev 1941) Davis 1948 * "'' Borrelia lonestari''" Barbour et al. 1996 * "''Ca.''

Borrelia mahuryensis ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" Binetruy et al. 2020 * ''

Borrelia mazzottii ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

'' ♦ Davis 1956 * "''

Borrelia merionesi ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

''" Hougen 1974 * "''

Borrelia microti ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

''" (Rafyi 1946) Davis 1948 * "''Ca.''

Borrelia mvumii ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

" Mitani et al. 2004 * "''

Borrelia myelophthora ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

''" (Steiner 1931) Ahrens & Muschner 1958 * "''Ca.''

Borrelia paulista ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

" Weck et al. 2022 * "''

Borrelia puertoricensis ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and a ...

''" Bermudez et al. 2021 * ''

Borrelia theileri ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

'' ♦ (Laveran 1903) Bergey et al. 1925 * ''

Borrelia tillae ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, Vector (epidemiology), vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause rela ...

'' ♦ Zumpt & Organ 1961 * ''

Borrelia venezuelensis ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, an ...

'' ♦ (Brumpt 1921) Brumpt 1922 * '' Borreliella americana'' (Rudenko et al. 2010) Adeolu & Gupta 2018 * "'' Borreliella andersonii''" (Marconi, Liveris & Schwartz 1995) Adeolu & Gupta 2014 * '' Borreliella carolinensis'' (Rudenko et al. 2011) Adeolu & Gupta 2015 * '' Borreliella kurtenbachii'' (Margos et al. 2013) Adeolu & Gupta 2015 * "'' Borreliella lusitaniae''" (Le Fleche et al. 1997) Adeolu & Gupta 2014 * "'' Borreliella tanukii''" (Fukunaga et al. 1997) Adeolu & Gupta 2014 * '' Borreliella sinica'' (Masuzawa et al. 2001) Adeolu & Gupta 2015 * "''Ca.'' Borreliella texasensis" (Lin et al. 2005) Adeolu & Gupta 2014

Vectors

Ticks

Hard ticks of the family

Ixodidae The Ixodidae are the family of hard ticks or scale ticks, one of the three families of ticks, consisting of over 700 species. They are known as 'hard ticks' because they have a scutum or hard shield, which the other major family of ticks, the 'so ...

are common vectors of ''Borellia'' bacteria and are the only type of ticks shown to transmit Lyme disease bacteria to humans. Some tick species of the ''Ambylomma'' genus are vectors of ''Candidatus'' Borrelia mahuryensis in South America. Other species are carried by soft ticks. The soft tick '' Ornithodoros'' carries the species of ''Borellia'' that cause relapsing fever. Another species, ''B. anserina'', is carried by the soft tick ''

Argas ''Argas'' is a genus of tick. Species * '' Argas abdussalami'' Hoogstraal & McCarthy, 1965 * '' Argas acinus'' Whittick, 1938 * '' Argas africolumbae'' Hoogstraal, Kaiser, Walker, Ledger, Converse & Rice, 1975 * '' Argas arboreus'' Kaiser, Hoo ...

''. Inside the ticks, the bacteria grow in the midgut and then travel to the salivary glands to be transmitted to a new host. Ticks can spread the bacteria to each other when co-feeding. If an animal has been infected by a tick and then is bitten by a second tick, the second tick can become infected. The bacteria are most commonly transmitted to humans through ticks in the nymph stage of development, because they are smaller and less likely to be noticed and removed. The ticks must have around 36 to 48 hours of contact with a host to successfully transmit the bacteria.

Lice

Lice Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a resul ...

that feed on infected humans acquire the ''Borrelia'' organisms that then multiply in the hemolymph and gut of the lice. 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. The U. S.

Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...

reported that no credible evidence shows that lice can carry ''Borrelia''.

Lyme disease

Of the 52 known species of ''Borrelia'', 20 belong to the Lyme disease group and are transmitted by ticks. Eight are known to cause

or Borreliosis. The major ''Borrelia'' species causing Lyme disease are ''

Borrelia burgdorferi ''Borrelia burgdorferi'' is a bacterial species of the spirochete class in the genus '' Borrelia'', and is one of the causative agents of Lyme disease in humans. Along with a few similar genospecies, some of which also cause Lyme disease, it ...

'', '' Borrelia afzelii'', and '' Borrelia garinii''. All species that cause Lyme disease are referred to collectively as ''B. burgdorferi'' ''sensu lato'', while ''B. burgdorferi'' itself is specified as ''B. burgdorferi'' ''sensu stricto''. ''B. burgdorferi'' was previously believed to be the only species to cause Lyme disease in the US, but ''B. bissettiae'' and a new species called ''B. mayonii'' cause Lyme disease in the US, as well. The remaining five human pathogenic species occur only in Europe and Asia.

Relapsing fever

Relapsing fever (RF) borreliosis often occurs with severe bacteremia. Twenty-five species of ''Borrelia '' are known to cause relapsing fever. While most species use the soft tick family

Argasidae The Argasidae are the family of soft ticks, one of the three families of ticks. The family contains 193 species, although the composition of the genera is less certain, and more study is needed before the genera can become stable. The currentl ...

as their vector, some outliers live in hard ticks or lice. Relapsing fever can be spread epidemically through lice or endemically through ticks. ''B. recurrentis'', a common species underlying relapsing fever, is transmitted by the human body

louse Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result ...

; no other animal reservoir of ''B. recurrentis'' is known. ''B. recurrentis'' infects the person via

mucous membranes A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

and then invades the bloodstream. Other tick-borne relapsing infections are acquired from other species, such as '' B. hermsii'', '' B. parkeri'', or '' B. miyamotoi'', which can be spread from rodents, and serve as a reservoir for the infection, via a tick vector. ''B. hermsii'' and ''

B. recurrentis ''Borrelia recurrentis'' is a species of ''Borrelia'', a spirochaete bacterium associated with relapsing fever. ''B. recurrentis'' is usually transmitted from person to person by the human body louse The body louse (''Pediculus humanus humanu ...

'' cause very similar diseases, although the disease associated with ''B. 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.

Diagnosis

Direct tests include culture of ''Borrelia'' from skin, blood, or cerebrospinal fluid (CSF), and detection of genetic material by

polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...

in skin, blood, or synovial fluid. Two-tiered serological testing is performed for differential diagnosis of ''Borrelia'' infection. The first-tier tests detect specific antibodies ( IgM and IgG together or separately) and include enzyme-linked

immunoassay An immunoassay (IA) is a biochemical test that measures the presence or concentration of a macromolecule or a small molecule in a solution through the use of an antibody (usually) or an antigen (sometimes). The molecule detected by the immunoass ...

s (e.g.

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...

s) and

immunofluorescent Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on microbiological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specifi ...

assays. Positive results for first-tier tests are confirmed using second-tier testing. The second tier consists of standardized immunoblotting, either by using

Western blot The western blot (sometimes called the protein immunoblot), or western blotting, is a widely used analytical technique in molecular biology and immunogenetics to detect specific proteins in a sample of tissue homogenate or extract. Besides detec ...

s or blots striped with diagnostically important purified antigens. Positive results for second-tier tests are confirmatory for the presence of ''Borrelia'' infection. Spirochetes can also be seen using Wright-stained blood smears.

References

External links

Borrelia
genomes and related information a
PATRIC
a Bioinformatics Resource Center funded b
NIAID

Borrelia Microbe Wiki Page

NCBI Borrelia Taxonomy Browser
{{Taxonbar, from=Q115528 Lyme disease Spirochaetes Bacteria genera