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*Longer, wider, helical spirochaetes with a linear chromosome and linear and circular plasmids
*Longer, wider, helical spirochaetes with a linear chromosome and linear and circular plasmids
*Obligate parasites transmitted by arthropod vectors
*Obligate parasites transmitted by arthropod vectors
*Cause systemic infections in many animals and humans
*Slow growth in specialised culture media
*Lyme disease
*Lyme disease
**Ticks transmit the infection to large mammals such as deer and sheep
**Ticks transmit the infection to large mammals such as deer and sheep
**''Ixodes ricinus'' is the most common tick vector in Europe
**''Ixodes ricinus'' is the most common tick vector in Europe
**Pathogenesis
***Virulence of the borreliae requires a change in expression of an outer membrane protein following ingestion of blood by the tick
***Borreliae multiply in the blood stream of susceptible hosts and disseminate throughout the body
***Localisation in joints, brain, nerves, eyes and heart can occur
***The associated lesions may be in part caused by the host immune response
**CLinical signs
***May be subclinical in endemic areas
***Clinical manifestation depends on the site of localisation of organisms
***Disease in dogs may cause fever, lethargy, arthritis, cardiac, renal or neurological disturbance
***Horses suffer similar clinical signs but also lameness, uveitis, nephritis, hepatitis and encephalitis
***Cattle and sheep may suffer from lameness
**Diagnosis
***Laboratory confirmation difficult due to low numbers of organisms and fastidious growth requirements
***History of exposure to ticks in an endemic region and clinical signs
***Rising antibody titre to ''Borrelia burgdorferi'' detected by ELISA
***Immunofluorescence
***Culture in Barbour-Stoenner-Kelly medium for 6 weeks under microaerophilic conditions
***PCR
**Treatment and control
***Amoxycillin and oxytetracycline in the acute phase; prolonged treatment in the chronic phase
***Tick control and removal
***Vaccines including whole cell bacterins and recombinant subunit vaccines available for dogs
===Avian spirochaetosis===
*Caused by ''Borrelia anserina''
*Acute, endemic disease of birds in tropical and subtropical regions
*Chickens, turkeys, pheasants, ducks and geese susceptible
*Transmitted by soft ticks of the ''Argas'' family, but also via contact with infected material such as blood and tissues
*Transmitted transovarially and trans-stadially via the tick population
*Outbreaks during peak tick activity during warm, humid conditions
*Fever, anaemia and wight loss occurs, with development of paralysis later
*Immunity is serotype specific
*Diagnosis using dark-field microscopy of buffy coat smears or immunodluorescence of blood or tissues
*Giemsa-stained smears and silver impregnation of tissues
*Isolation of borreliae by inoculation of embryonated eggs or chicks
*Antibiotic treatment
*Inactivated vaccines available
===''Brachyspira'' and ''Serpulina''===
[[Brachyspira hyodysenteriae]]
[[Brachyspira hyodysenteriae]]