The ''Borrelia'' species are longer, wider, helical ''[[Spirochaetes species - Overview|spirochaetes]]'' with a linear chromosome and linear and circular plasmids. They are obligate parasites transmitted by arthropod vectors. They cause systemic infections in many animals and humans. | The ''Borrelia'' species are longer, wider, helical ''[[Spirochaetes species - Overview|spirochaetes]]'' with a linear chromosome and linear and circular plasmids. They are obligate parasites transmitted by arthropod vectors. They cause systemic infections in many animals and humans. |