Borreliosis [bore-El-ee-Oh-sis] (Lyme disease) is caused by a slow-growing spirochaetal bacterium of the Borrelia genus.

There are hundreds of strains and sub-types of Borrelia bacteria. Borrelia burgdorferi sensu stricto (Bb.s.s.) is the strain of bacterium which caused an outbreak of infection in Old Lyme, Connecticut, in the US, in 1975. This is how the term Lyme disease came into being. However, in 1909 Arvid Afzelius associated the tick Ixodes ricinus with an expanding rash (Erythema Migrans) and in Europe the disease has been known since the 1980′s under a variety of names including Erythema Migrans, Acrodermatitis Chronica Atrophicans and Bannwarth’s syndrome.

To date Borrelia burgdorferi (Bb) can be divided into at least 15 genospecies. B. afzelii, B. bavariensis, B. burgdorferi sensu stricto (s.s.), B. garinii and B. spielmanii are all known to be capable of causing disease. There is currently a lack of consistent evidence to determine whether B. bissettii, B. lusitaniae and B. valaisiana also cause disease. The group as a whole is referred to as B. burgdorferi sensu lato (Bb s.l.). Borreliosis is an umbrella term to cover infection of any genospecies.

In the UK Borreliosis predominantly causes neurological complications and cases of Lyme-associated arthritis are uncommon compared to the US.

Borrelia Burgdorferi Spirochaete