Medicine chapters
Leptospirosis
Leptospirosis is a spirochaete infection of animals that humans catch from water or soil contaminated by animal urine, especially after floods. Learn its epidemiology, biphasic illness, Weil disease, diagnosis and treatment.
- Leptospirosis is an animal-to-human infection (zoonosis) due to the spirochaete Leptospira interrogans, excreted in the urine of rats and other animals; humans catch it through cut skin or mucosa in contaminated water or soil, so outbreaks follow floods and heavy rain.
- Illness is biphasic: a septicaemic phase with high fever, severe calf myalgia and conjunctival suffusion, then an immune phase with aseptic meningitis; severe disease (Weil disease) adds jaundice, acute kidney injury and bleeding, and pulmonary haemorrhage is a major killer.
- Confirm with PCR or culture early, IgM ELISA or MAT (fourfold rise) later; treat mild disease with doxycycline and severe disease with IV penicillin or ceftriaxone.
On this page
Overview
Leptospirosis is one of the most widespread zoonoses in the world. It is common in warm, humid tropical regions, and outbreaks follow monsoon rains and flooding, as seen in Pakistan after major floods.
Most infections are mild or silent, but severe disease (Weil disease) causes jaundice, kidney failure and bleeding, and pulmonary haemorrhage can kill quickly. Because the early illness looks like dengue, malaria or typhoid, it is often missed.
Epidemiology
Agent
- Leptospira interrogans: a thin, tightly coiled, motile spirochaete with hooked ends.
- Seen with dark-field microscopy or silver stains; does not Gram stain well.
- More than 200 serovars. Important ones: icterohaemorrhagiae (rats; classically linked to Weil disease), canicola (dogs), hardjo (cattle), pomona (pigs).
- Immunity after infection is serovar-specific.
Reservoir and source
- Rodents (especially rats) are the most important reservoir; they carry leptospires in their kidneys and shed them in urine, often for life.
- Dogs, cattle, buffaloes, pigs, goats and sheep can also carry them.
- Leptospires survive for weeks in warm fresh water and moist soil.
Transmission
- Indirect contact (commonest): wading or swimming in, or working with, water or mud contaminated with animal urine; organisms enter through cuts, abrasions, or intact mucous membranes (eyes, mouth, nose).
- Direct contact with urine, blood or tissues of infected animals.
- Occasionally by swallowing contaminated water.
- Person-to-person spread is very rare.
Outbreaks follow heavy rain and flooding, when rat urine contaminates large areas of standing water and people wade through it with cuts on their feet and legs.
Risk groups
| Group | Examples |
|---|---|
| Occupational | Farmers, rice-paddy and sugarcane workers, sewer and drain workers, abattoir workers, butchers, veterinarians, miners, fish farmers |
| Environmental | Flood victims, slum dwellers with poor drainage and many rats |
| Recreational | Swimming, rafting, fishing in fresh water |
Incubation
- About 10 days on average (range about 2–30 days; most within 1–2 weeks).
Pathophysiology
- Leptospires spread through the blood to every organ in the first week (leptospiraemic phase).
- They damage the lining of small blood vessels (vasculitis), causing bleeding, leaky capillaries and organ dysfunction.
- Kidney: interstitial nephritis and tubular damage. A typical pattern is non-oliguric AKI with potassium wasting (hypokalaemia).
- Liver: jaundice is out of proportion to liver cell damage; bilirubin is very high but transaminases rise only mildly. Hepatocellular necrosis is not prominent.
- Muscle: focal necrosis explains calf pain and a raised CK.
- Lung: haemorrhagic pneumonitis.
- From the second week, antibodies appear and organisms clear from blood but persist in the kidney (urine), eye and CSF, causing the immune phase.
Clinical features
Anicteric leptospirosis (most cases, 90% or more)
Phase 1: septicaemic (leptospiraemic), about 1 week
- Abrupt high fever, rigors, severe headache (often frontal, retro-orbital).
- Severe myalgia, especially of the calves and lower back; calf tenderness on squeezing.
- Conjunctival suffusion: reddened conjunctivae without pus; subconjunctival haemorrhage may occur.
- Nausea, vomiting, abdominal pain, dry cough, rash.
Short improvement (1–3 days), then:
Phase 2: immune phase
- Fever returns; aseptic (lymphocytic) meningitis is common.
- Uveitis (can appear weeks to months later).
- Leptospires appear in the urine.
Icteric leptospirosis: Weil disease (5–10%)
- The two phases merge; illness is severe from the start.
- Jaundice (deep, often orange-tinged).
- Acute kidney injury (oliguric or non-oliguric).
- Bleeding: epistaxis, haemoptysis, GI bleeding, skin petechiae; thrombocytopenia.
- Myocarditis, arrhythmias, hypotension.
- Severe pulmonary haemorrhage syndrome: haemoptysis, breathlessness, ARDS; a leading cause of death.
Fever + conjunctival suffusion + calf tenderness + jaundice + AKI after flood or sewage exposure is leptospirosis (Weil disease) until proved otherwise.
Poor prognostic features
- Pulmonary haemorrhage / ARDS and need for ventilation
- Oliguric kidney failure, hyperkalaemia
- Hypotension, myocarditis, arrhythmias
- Altered consciousness
- Older age; multi-organ failure
Investigations
Supporting findings
| Test | Typical result |
|---|---|
| FBC | Neutrophil leucocytosis (unlike dengue and typhoid), thrombocytopenia in severe cases |
| LFTs | Raised bilirubin (conjugated) with only mild rise in AST/ALT |
| CK | Raised (muscle involvement); helps separate it from viral hepatitis |
| Renal | Raised urea and creatinine, hypokalaemia; urine shows protein, red cells, casts |
| CSF (immune phase) | Lymphocytes, normal glucose |
| CXR | Patchy alveolar shadowing in pulmonary haemorrhage |
In viral hepatitis the transaminases are in the thousands; in leptospirosis the bilirubin is high but transaminases only modestly raised, and CK is high.
Confirming the diagnosis
| Week | Best test | Sample |
|---|---|---|
| Week 1 | PCR (leptospiral DNA); culture on special semisolid media (slow, weeks); dark-field microscopy (unreliable) | Blood, CSF |
| From about day 5–7 | IgM ELISA (rapid tests such as dipsticks also available) | Serum |
| Week 2 onwards | Culture or PCR of urine | Urine |
| Paired sera | Microscopic agglutination test (MAT): fourfold rise in titre, or a single high titre | Serum |
- MAT is the reference (gold-standard) serological test but needs live cultures of many serovars, so it is done only in reference laboratories, and the diagnosis is often confirmed retrospectively.
Differential diagnosis
| Condition | How it differs |
|---|---|
| Dengue | Aedes exposure, retro-orbital pain, leucopenia, NS1 positive |
| Malaria | Rigors, film or RDT positive |
| Enteric fever | Gradual onset, relative bradycardia, leucopenia, blood culture |
| Viral hepatitis (A, E) | Fever settles as jaundice appears; transaminases very high |
| CCHF / other haemorrhagic fevers | Tick or animal blood exposure; very high AST, severe early bleeding |
| Hantavirus, rickettsial infection, sepsis, acute cholangitis | History and specific tests |
Management
Antibiotics (start early, even before confirmation)
| Severity | Treatment |
|---|---|
| Mild (outpatient) | Oral doxycycline for 7 days (amoxicillin or azithromycin in pregnancy and children) |
| Severe (Weil disease, admitted) | IV benzylpenicillin or IV ceftriaxone (cefotaxime or doxycycline IV are alternatives) |
Do not wait for MAT results before treating. Serology is often negative in the first week, and the diagnosis is frequently confirmed only in retrospect.
- A Jarisch-Herxheimer reaction (fever, rigors, hypotension after the first antibiotic dose) can occur, as in other spirochaete infections.
Supportive care
- Careful fluids and electrolytes (replace potassium in non-oliguric AKI).
- Dialysis for severe or oliguric kidney failure, hyperkalaemia or fluid overload; early dialysis improves outcome.
- Platelets and blood for bleeding.
- Ventilation (lung-protective) for pulmonary haemorrhage; ICU care for shock and myocarditis.
The kidney injury of leptospirosis is often non-oliguric with hypokalaemia; it usually recovers fully with supportive care and dialysis if needed.
Prevention
- Rodent control, safe waste disposal, good drainage.
- Protective clothing (boots, gloves) for farmers, sewer workers and flood workers; cover cuts.
- Avoid wading or swimming in floodwater and stagnant water.
- Chemoprophylaxis: doxycycline 200 mg once a week during exposure (for example soldiers, rescue workers, people in flooded areas).
- Vaccination of dogs and livestock; human vaccines exist in a few countries but are serovar-specific.
"Rats, Rain, Red eyes, Renal failure": rat urine, rainy-season floods, conjunctival suffusion, and kidney injury in Weil disease.
Expect: the organism and reservoir (rats, urine); entry through skin abrasions in floodwater; high-risk occupations; biphasic illness; conjunctival suffusion and calf tenderness; Weil disease (jaundice, AKI, bleeding) and pulmonary haemorrhage as the main killer; neutrophil leucocytosis, high CK, high bilirubin with mild transaminase rise; PCR or culture early, IgM ELISA and MAT later; penicillin or ceftriaxone for severe disease, doxycycline for mild disease and weekly doxycycline prophylaxis.
Quick revision
- Leptospira interrogans; spirochaete with hooked ends; dark-field microscopy.
- Rats shed it in urine; floods, rice fields, sewers.
- Enters through cut skin or mucosa; man-to-man spread rare.
- Phase 1: fever, calf pain, conjunctival suffusion; phase 2: aseptic meningitis, uveitis.
- Weil disease: jaundice + AKI + bleeding; pulmonary haemorrhage kills.
- Labs: neutrophilia, high CK, high bilirubin, mild AST/ALT, hypokalaemia.
- PCR/culture early; IgM ELISA; MAT fourfold rise is the reference test.
- Doxycycline (mild); IV penicillin or ceftriaxone (severe); doxycycline 200 mg weekly as prophylaxis.
Written by The House Job from standard references (Kumar and Clark's Clinical Medicine; Park's Textbook of Preventive and Social Medicine; Levinson's Review of Medical Microbiology and Immunology).
FAQ
How do people catch leptospirosis?
Through cuts in the skin or the lining of the eyes, nose and mouth when they contact water or mud contaminated with the urine of infected rats or other animals.
What is Weil disease?
The severe form of leptospirosis, with jaundice, acute kidney injury and bleeding, often with myocarditis and lung haemorrhage.
Which test confirms leptospirosis?
In the first week, PCR or culture of blood; later, IgM ELISA. The microscopic agglutination test showing a fourfold rise in titre is the reference test.
What is the treatment of severe leptospirosis?
Intravenous benzylpenicillin or ceftriaxone with supportive care, including dialysis for kidney failure and ventilation for lung haemorrhage.