Overview
Leptospirosis is a zoonotic infection caused by the spirochaete Leptospira interrogans most commonly from rats. It is a biphasic illness with initial bacteraemia followed by immune phenomena.
Weil’s disease is a severe form of leptospirosis characterised by jaundice and acute kidney injury.
Pathophysiology
Most cases are due to exposure to contaminated water or soil, with the entry of Leptospira interrogans through the skin or mucous membranes. Infected animals excrete the organism in their urine. Upon entry, it circulates in the blood and invades organs including the liver causing necrosis and jaundice, and the kidneys causing acute tubular necrosis and acute interstitial nephritis.
Epidemiology
- Leptospirosis is uncommon in the UK, with 92 cases reported in 2017
- However, it is more common in countries with warmer climates
Risk Factors
- Exposure to animal waste/sewage – such as farmers and sewage workers
- Returning travellers – particularly from tropical countries
Presentation
The incubation period is around 7-12 days:
- First (bacteraemic) phase – lasts up to 7 days:
- Fever
- Flu-like symptoms – such as myalgia, malaise, headaches, nausea etc.
- Conjunctival suffusion (redness) – pathognomonic and seen in both phases
- Second (immune) phase – may last up to a month:
- Acute kidney injury
- Aseptic meningitis
- Hepatitis – jaundice, hepatomegaly
Investigations
Overview
Some key investigations include:
- Enzyme-linked immunosorbent assay (ELISA):
- Positive during the immune phase as this is when antibodies are made
- Polymerase chain reaction (PCR):
- May be useful in the bacteraemic phase and may be positive for Leptospira DNA
- Culture of the blood, cerebrospinal fluid, urine etc.:
- Culturing is slow (takes up to several weeks) and insensitive
Management
Overview
- 1st-line: high-dose benzylpenicillin
- Doxycycline is an alternative
