Leptospirosis (Weil's Disease)
Summary
Leptospirosis is a spirochaetal zoonosis caused by Leptospira interrogans. It is globally the most common zoonosis. Transmission occurs via contact with soil or water contaminated by rodent urine. 90% of cases are mild (anicteric). 10% progress to Weil's Disease (icteric), characterised by Liver failure (Jaundice), Kidney failure (AKI), and Haemorrhage. The hallmark sign is Conjunctival Suffusion (Red eyes without pus). [1,2]
Clinical Pearls
Conjunctival Suffusion: This is the "money sign". It presents as bilateral redness of the conjunctiva without discharge. It typically appears on day 3-4. It is distinct from the "sticky eye" of bacterial conjunctivitis.
The "Calf Pain" Clue: Severe myalgia, specifically localised to the gastrocnemius (calves) and lumbar region, is highly characteristic. It can be severe enough to mimic rhabdomyolysis or acute abdomen.
Biphasic Illness: The disease often has a "saddle-back" fever.
- Phase 1 (Septic): 3-7 days. Fever/Myalgia. (Spirochaetes in blood).
- Recovery: 1-3 days afebrile.
- Phase 2 (Immune): Fever returns + Organ failure + Uveitis. (Spirochaetes in urine/tissues).
Demographics
- Global: 1 million cases/year (mostly Tropics).
- UK/US: Associated with:
- Occupational: Farmers, Sewage workers, Vets.
- Recreational: Fresh water sports (Triathlon, Kayaking, Wild swimming).
- Reservoir: Rats are the primary host (asymptomatic renal carriage).
Mechanism
- Entry: Spirochaetes penetrate abraded skin or mucous membranes (eyes/nose) from contaminated water.
- Dissemination: Hematogenous spread (Leptospiremia).
- Vasculitis: The bacteria damage the endothelium of small blood vessels (Capillary vasculitis).
- Kidney: Acute Tubulointerstitial Nephritis (ATN).
- Liver: Hepatocellular damage (but minimal cell death, hence architecture is preserved despite deep jaundice).
- Lungs: Alveolar Capillary Bleeding (Pulmonary Haemorrhage).
Anicteric Form (90%) - "The Flu-Like Phase"
Icteric Form (Weil's Disease - 10%)
- Eyes: Red, suffused conjunctivae.
- Skin: Jaundice, Purpuric rash, "Rose spots" (rare).
- Chest: Crackles (Pulmonary haemorrhage).
- Abdomen: Hepatomegaly (20%). Splenomegaly (rare).
Biochemistry
- FBC: High WCC (Neutrophilia), Thrombocytopenia (50%).
- U&E: High Creatinine/Urea. Potassium often normal/low.
- LFTs: High Bilirubin (can be >500), but modestly elevated ALT/AST (less than 200). High ALP.
- CK: High (Myositis).
Microbiology (Timing is Critical)
- PCR (Blood/Urine): Diagnostic choice in first 7 days.
- Serology (MAT): Microscopic Agglutination Test. Detects IgM. Only positive after 7-10 days. Requires paired samples (4-fold rise).
- Culture: Difficult and slow (requires special media). Rarely done.
Management Algorithm
SUSPECTED LEPTOSPIROSIS
(Exposure + Fever + Red Eyes + Calf Pain)
↓
ASSESS SEVERITY (Jaundice/AKI?)
┌─────────┴─────────┐
MILD SEVERE
(Anicteric) (Weil's)
↓ ↓
• Oral **Doxycycline** • Admit to ITU/HDU
(100mg BD x 7d) • IV **Penicillin G**
or (1.2g QDS)
• Oral Amoxicillin or
(500mg TDS x 7d) IV Ceftriaxone
↓
SUPPORTIVE CARE
• Dialysis for AKI
• Ventilation for
Pulmonary Bleed
Jarisch-Herxheimer Reaction
- A transient worsening of symptoms (fever spike, hypotension) shortly after starting antibiotics. Caused by massive release of bacterial toxins as spirochaetes die. Monitor closely.
Prophylaxis
- Doxycycline 200mg weekly is effective for short-term high-risk exposure (e.g., soldiers fording rivers, relief workers in floods).
- Pulmonary Haemorrhage Syndrome (LPHS): The main killer. Massive alveolar bleeding -> ARDS. Mortality >50%.
- Renal Failure: Usually reversible, but may require temporary dialysis.
- Uveitis: Can occur weeks to months after recovery (Immune mediated).
- Mild: Excellent. Resolves in 1 week.
- Severe: Mortality 10-15%. However, liver and renal function usually recover fully in survivors (no chronic cirrhosis/CKD).
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Leptospirosis | UKHSA (PHE) | Risk assessment and diagnostic algorithm. |
| Management | WHO | Antibiotic protocols. |
Landmark Evidence
1. Bharti et al (Lancet ID 2003)
- The definitive review describing the global burden, biphasic nature, and management of severe disease.
What is Weil's Disease?
It is an infection caused by bacteria spread by animals, most commonly rats. The rats carry the germs in their kidneys and pee them out into water or soil.
How do I catch it?
It is not from a rat bite. You catch it if contaminated water gets into your eyes, mouth, or a stray cut on your skin. Common ways are wild swimming, falling in a canal, or fishing.
What are the symptoms?
It starts like a terrible flu: high fever, shivering, and severe aches in your calf muscles. A tell-tale sign is that the whites of your eyes turn bright red. In severe cases, you turn yellow (jaundice) and stop passing urine.
Is it treatable?
Yes. Antibiotics work well. If you catch it early, tablets will cure it. If you get really sick, we can support your kidneys with dialysis until the antibiotics work.
Primary Sources
- Bharti AR, et al. Leptospirosis: a zoonotic disease of global importance. Lancet Infect Dis. 2003.
- Day N, et al. Treatment of leptospirosis. Curr Opin Infect Dis. 2005.
- Goarant C. Leptospirosis: the complex synergy between soil, mammals, microorganisms and human health. PLoS Pathog. 2016.
Common Exam Questions
- Diagnosis: "Sewer worker + Fever + Jaundice + Red Eyes?"
- Answer: Leptospirosis (Weil's Disease).
- Vector: "Animal reservoir?"
- Answer: Brown Rat (Rattus norvegicus).
- Treatment: "Antibiotic of choice?"
- Answer: Doxycycline (Mild) / BenPen (Severe).
- Reaction: "Fever spike after antibiotics?"
- Answer: Jarisch-Herxheimer Reaction.
Viva Points
- Why is bilirubin high but ALT low?: Leptospires damage the hepatocyte membrane transporter (causing jaundice) but do not cause massive cell necrosis (so enzymes don't leak out as much as in viral hepatitis).
- Urine testing: Why check urine? Because the bacteria live in the kidneys and are shed in urine (leptospiruria) long after they clear from the blood.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.