see also:

• zoonoses
• NSW Govt fact sheet

• Leptospirosis is caused by a cork-screw shaped bacteria of the genus Leptospira.
• It is transmitted by the urine and semen of an infected animal and is contagious as long as the urine is still moist
• human disease is also called Weil's disease (1st described in 1886) if it causes jaundice, renal failure and bleeding, and if it also causes haemoptysis, it is called severe pulmonary haemorrhage syndrome both of which have high mortality rates

• 21 species of Leptospira have been identified of which 13 cause human disease
• approx. 250 pathogenic serovars of Leptospira are recognized
• leptospires survive best in fresh water, damp alkaline soil, vegetation, and mud with temperatures higher that 22 °C
• concentrations tend to get higher in residual pools of waters during droughts
• Leptospira bacteria are quickly killed by soap, disinfectants, and drying.

• around 10 million people are infected worldwide each year and around 60,000 die
• disease was brought to America by the first Europeans and is thought to have killed over half the Native American population whose practices were high risk for catching the disease
• most common in the tropics where there is year round high rainfall, but occurs elsewhere, usually seasonally, while outbreaks can occur in slums infested with rodents or following floods
• relatively rare in Australia, but it is more common in warm and moist regions such as northeastern NSW and Queensland
• it was common during trench warfare in World War I
• highest risk age groups: children over 5 yrs to young adults
  • up to 30% of some urban children populations in USA have antibodies
• some infected host animals have lifelong excretion of leptospires in the urine, but most probably only for up to a year
• primary hosts
  • rats, mice, and moles
• secondary hosts
  • wide range of mammals including some marine mammals
• human infection
  • humans become infected through contact with water, food, or soil that contains urine from these infected animals, either by ingesting or through open wound, eye or nose contact
  • hence river sailors, surfers, white water paddlers, sewer workers, campers, hikers, gardeners, farmers, vets, abattoir workers and those who work on derelict buildings are a particular risk
  • person-to-person transmission is rare
• habitats
  • habitats most likely to carry infective bacteria includes muddy riverbanks, gullies, and muddy livestock rearing areas where there is a regular passage of wild or farm mammals
• seasonal nature
  • incidence varies with rainfall

• incubation period usually 7-12 days (2 to 30 days)
• 90% have mild disease

• sudden onset with fever, chills, intense headaches, severe myalgias, abdominal pain, conjunctival injection, and sometimes a skin rash
• lasts 3-7 days then, usually the patient is asymptomatic for 3–4 days (some with severe illness do not have the asymptomatic phase)

• fever returns
• in the 10% who develop severe disease:
  • meningitis is a core feature +/- encephalitis
  • extreme fatigue
  • hearing loss
  • respiratory distress
  • acute renal impairment
  • Weil's disease if it causes jaundice, renal failure and bleeding (10% mortality)
  • severe pulmonary haemorrhage syndrome if it also causes pulmonary haemorrhage (50% mortality)

• occasionally the bacteria can persist in the eyes and cause chronic eye inflammation
• recovery from leptospirosis infection can be slow. People can have a chronic-fatigue-like illness that lasts for months. Others can have persistent headache or depression

• NB. LFTs may be normal or mildly elevated even when jaundiced
• organism can be found in blood (days 0 to 7), in CSF (days 4 to 10), then it moves to urine after day 10
• ELISA serology two specimens, 2 weeks apart:
  • > 4x rise, or,
  • a single Leptospira microagglutination titre of 400 or greater with a positive IgM result
• PCR
• gold standard is the serologic MAT (microscopic agglutination test) but is laborious and expensive
• culture is rarely done as it takes 3 wks to 3 months to grow
• in Victoria, it is a notifiable disease

• mild cases:
  • antibiotics include penicillin G, ampicillin, amoxicillin and doxycycline
• severe cases:
  • cefotaxime or ceftriaxone
  • may require dialysis for hyperkalaemia
  • corticosteroids in gradually reduced doses (eg prednisolone) for 7–10 days is recommended by some specialists in cases of severe hemorrhagic effects