''Borrelia lusitaniae'' is a bacterium of the

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

class of the genus'' Borrelia'', which has a diderm (double-membrane) envelope. It is a part of the ''

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 m ...

'' ''sensu lato'' genospecies and is a

Gram-negative bacterium Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists of ...

. ''B. lusitaniae'' is tick-borne; he type strain is PotiB2. It can be

pathogenic In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term ...

, being involved in cases of Lyme borreliosis. A species of tick, ''

Ixodes ricinus ''Ixodes ricinus'', the castor bean tick, is a chiefly European species of hard-bodied tick. It may reach a length of when engorged with a blood meal, and can transmit both bacterial and viral pathogens such as the causative agents of Lyme disea ...

'', is the host of ''B. lusitaniae''. It is thought to have originated from Portugal and has since spread to parts of Europe and North Africa. Lizards of the family

Lacertidae The Lacertidae are the family of the wall lizards, true lizards, or sometimes simply lacertas, which are native to Afro-Eurasia. It is a diverse family with at about 360 species in 39 genera. They represent the dominant group of reptiles found ...

are now believed to be important reservoir hosts of this bacterium.

Origin and distribution

While ''B. lusitaniae'' is distributed throughout countries in Europe and North Africa, it is the sole species of the Lyme borreliosis group in southern

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

. Lizards of the family Lacertidae are believed to be important reservoir hosts of ''B. lusitaniae''. They were first isolated in Portugal in 1993. These lizards that include the

sand lizard #REDIRECT Sand lizard {{redirect category shell, {{R from alternative capitalisation{{R from move ...

and common wall lizard are known to be highly structured phylogeographically. Migration is very limited between the lizard populations from different localities and it has shed light into the evolution and

epidemiology Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and Risk factor (epidemiology), determinants of health and disease conditions in a defined population, and application of this knowledge to prevent dise ...

of ''B. lusitaniae''. The pronounced population structure of ''B. lusitaniae'' over a short geographic distance (southern Portugal) by

housekeeping genes In molecular biology, housekeeping genes are typically constitutive genes that are required for the maintenance of basic cellular function, and are gene expression, expressed in all cells of an organism under normal and patho-physiological condit ...

indicates that the migration rates of ''B. lusitaniae'' are rather low, because the distribution of Mediterranean lizard populations is highly parapatric. Different populations of ''B. lusitaniae'' are known. Seven strains of ''B. lusitaniae'' ''sp. nov.'' have been isolated from ''Ixodes ricinus'' ticks in Portugal, the

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Ukraine Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...

, and

Belarus Belarus, officially the Republic of Belarus, is a landlocked country in Eastern Europe. It is bordered by Russia to the east and northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Belarus spans an a ...

. Local populations have diverged through vicariance, because climate change after the last ice age generated ecological barriers between

Mafra Mafra is a Czech media group that publishes printed and internet media, headquartered in Prague, Czech Republic. From 2013 to 2023, it was a subsidiary of Agrofert holding conglomerate owned by trust of Andrej Babiš, the former Prime Ministe ...

and Grândola. In more northern or eastern countries, ''B. lusitaniae'' has been detected at only a few sites, at which it infects ticks less frequently than it does on the Mediterranean coast, although in Morocco and Tunisia, 96.6-100% of the ''Borrelia'' species present were ''B. lusitaniae''.

In lizards

Because lizards are considered important reservoir hosts of ''B. lusitaniae'', their limited dispersal affects the migration rates of ''B. lusitaniae''. This results in the fine-scale geographic structure of this tick-borne bacterium. Although ''I. ricinus'' ticks infected with ''B. lusitaniae'' may be dispersed rapidly over long distances when feeding on mobile hosts, such as migratory birds, this is unlikely to be an important process in the effective dispersal of ''B. lusitaniae''. Feeding tick larvae apparently do not acquire ''B. lusitaniae'' from vertebrate species other than lizards. However, ''B. lusitaniae''-infected nymphs that feed on long-distance migrants give rise to hunting adult ticks that subsequently feed on larger animals, such as deer, which are not reservoir-competent for any of the species of the Lyme borreliosis group of spirochetes. Therefore, only larvae and nymphs that feed on lizards maintain the cycles of'' B. lusitaniae''. So, the migration rates of ''B. lusitaniae'' are determined by those of lizards.

In humans

To date, the reservoir of'' B. lusitaniae'' has not been fully defined, and little is known about the ecology of this genospecies. It is known to cause experimental disease in mouse models, suggesting that some strains could also be connected with human Lyme borreliosis. The first known isolate of ''Borrelia'' was in Portugal. A 46-year-old woman from the

Lisbon Lisbon ( ; ) is the capital and largest city of Portugal, with an estimated population of 567,131, as of 2023, within its administrative limits and 3,028,000 within the Lisbon Metropolitan Area, metropolis, as of 2025. Lisbon is mainlan ...

area presented with skin lesions on her left thigh that had persisted about 10 years. Molecular analysis of the patient isolate allowed the classification of the strain to ''B. lusitaniae'', a genospecies previously thought to be nonpathogenic in humans The woman had a weak

serological Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection (against a given mi ...

response, which is present in a high percentage of patients with unspecific and long-lasting skin manifestations. This suggests a clinical pattern for ''B. lusitaniae'' different from those for other ''Borrelia'' spp. in the Portuguese population compared to date .

Plasmids

The

plasmid A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria and ...

profiles of ''B. lusitaniae'' strains usually range from 19 to 76 kb. In the case of ''B. lusitaniae'', the number of plasmids is quite low and the species lacks all the small plasmids described for the other'' Borrelia'' species with medical importance in Lyme borreliosis. Because most of the'' Borrelia ''virulence genes are located on plasmids, including genes that encode for OspC, Erps, and CRASP proteins, the low number of these genetic elements in ''B. lusitaniae'' strains could be associated with the lower infectivity reported for this species since only two human isolates have been found so far. Furthermore, the number (0.04/100,000 inhabitants) of reported cases in Portugal is not as high as in other European countries despite a high reported infection prevalence of ''B. lusitaniae'' in ticks.

References

External links