Borrelia burgdorferi

Lyme disease
- Caused by Borrelia burgdorferi
- Reported in humans, dogs, horses, cattle, sheep
- Ticks are the vector, which acquire the infection from small rodents, the reservoir hosts
- Ticks transmit the infection to large mammals such as deer and sheep
- 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