Leptospira was previously classified into pathogenic and non-pathogenic species.
The Leptospira interrogans, the pathogenic species had many serovers.
The current classification is done based on genetic relatedness.
Host and carriers:
Most important carrier of this infection is rodents and other small animals. Leptospira causes chronic renal infection in these animals, causing prolonged shedding of the bacteria in the urine, often lifelong.
Other domestic and wild animals could get infected from these carriers.
Humans are the dead-end host. Human to human transmission has not been reported.
Humans can get infected from contact with contaminated water or animal products/urine.
After entering the blood, it causes systemic vasculitis, which facilitates the entry of the bacteria into various tissues. The incubation period is approx ten days (range 2-26 days)
Sign and symptoms:
Most Leptospira infections are subclinical and self-limiting.
The mean incubation period is approx ten days.
The disease often follows two phases (although it may not occur in all patients). A septicaemic phase, in which the bacteria could be found in the blood, usually manifests with
- Fever and flu-like illness
- Myalgia (calf, lumber)
- Conjunctival suffusion
- Upper respiratory tract symptoms
- Gastrointestinal symptoms
- Pretibial maculopapular rash
- Lymphadenopathy, and
This phase is followed by a remission of fever before the immune phase starts.
In the immune phase Leptospira disappears from the blood and IgM appears.
This phase shows signs and symptoms of organ involvement –
- Renal impairment/failure,
- Hepatic impairment/failure,
- Cardiac arrhythmia,
- Pulmonary manifestation (could be haemorrhagic),
- Meningitis (aseptic),
- Eye involvement (photophobia, pain, uveitis),
- Lymphadenopathy and
- In immune phase (80% cases).
- Headache (frontal, bi-temporal), photophobia.
- Lymphocytic pleocytosis, Protein – mild elevation, glucose – normal.
- The severe form of Leptospira infection may start immediately after the acute phase in some cases.
- High fever and rapid onset of organ failure.
- Liver failure- conjugated bilirubinaemia, ALT usually <200 IU/L.
- Renal impairment – nonolguric hypokalaemia, impaired sodum reabsorption.
- Thrombocytopenia; no DIC.
- Severe pulmonary haemorrhage syndrome.
- Up to 50% in hospitalised patients.
- The adverse outcome is associated with – older age, CNS involvement, jaundice and renal failure.
Leptospira can be isolated from blood, CSF, Peritoneal fluid etc for up to 10 days (longer from urine). However, culture and microscopy has low sensitivity. Dark ground microscopy was used to look for Leptospira.
Culture media- EMJH media
Stain – Immunofluorescence stain (see image, from CDC, PHIL), silver stain etc.
Identification can also be done using – 16S ribosomal RNA PCR, PFGE etc.
Other supportive measures
- renal suppport
- Correcting electrolyte imbalance etc
- Avoid high risk exposure
- Animal immunisation
- Human immunisation (less common)
- Weekly doxycycline (200 mg) Prophylaxis