Leptospirosis is caused by the spirochaete Leptospira interrogans (serogroup L. icterohaemorrhagiae), classically being spread by contact with infected rat urine.

Epidemiology

• leptospirosis is commonly seen in questions referring to sewage workers, farmers, vets or people who work in an abattoir
• however, on an international level, leptospirosis is far more common in the tropics so should be considered in the returning traveller

Weil's disease should always be considered in high-risk patients with hepatorenal failure

Features

• the early phase is due to bacteraemia and lasts around a week
  • may be mild or subclinical
  • fever
  • flu-like symptoms
  • subconjunctival suffusion (redness)/haemorrhage
• second immune phase may lead to more severe disease (Weil's disease)
  • acute kidney injury (seen in 50% of patients)
  • hepatitis: jaundice, hepatomegaly
  • aseptic meningitis

Investigation

• serology: antibodies to Leptospira develop after about 7 days
• PCR
• culture
  • growth may take several weeks so limits usefulness in diagnosis
  • blood and CSF samples are generally positive for the first 10 days
  • urine cultures become positive during the second week of illness

Management

• high-dose benzylpenicillin or doxycycline