What are the diagnostic criteria and treatment options for Weil's disease (Leptospirosis)?

Weil's Disease (Severe Leptospirosis) Diagnosis

Diagnose Weil's disease based on clinical suspicion from characteristic features and begin treatment immediately without waiting for laboratory confirmation, as serologic tests only become positive 6-10 days after symptom onset—too late to prevent life-threatening complications. 1, 2

Clinical Diagnostic Criteria

Characteristic Clinical Triad

• Sudden onset fever with severe general malaise and muscular pain (especially calf muscles) 1, 3
• Conjunctival suffusion (distinctive finding that should immediately raise suspicion) 1, 2
• Exposure history: Contact with urine-contaminated water, flooding, occupational animal exposure, or recreational water sports 1, 4

Severe Disease Features (Weil's Disease)

• Jaundice with hepatorenal syndrome 1, 5
• Hemorrhagic manifestations due to capillary fragility (despite often normal clotting studies) 1, 5
• Biphasic illness pattern: Initial bacteremic phase (4-7 days) followed by immune phase with fever, severe myalgia, and potential organ failure 1, 2

Laboratory Findings for Early Diagnosis

Non-Specific Initial Tests (Available Immediately)

• Urinalysis: Proteinuria and hematuria 1
• Complete blood count: Polymorphonuclear leukocytosis with neutrophilia, thrombocytopenia, anemia if hemorrhage present 1, 3
• Liver function tests: High bilirubin with only mild transaminase elevation 1
• Renal function: Biochemical evidence of renal failure 1
• Elevated erythrocyte sedimentation rate 3

Confirmatory Tests (Not Useful for Early Treatment Decisions)

• Serology (IgM ELISA and MAT): Earliest positives appear 6-10 days after symptom onset; IgM titer >1:320 is suggestive, 1:80-1:160 consistent with early infection but may represent cross-reactions 1
• Blood cultures: Only useful if taken within first 5 days before antibiotics, must be kept at room temperature before dispatch to reference laboratory 1, 2
• Convalescent serology: Required >10 days after symptom onset for confirmation 1

Treatment Algorithm

Immediate Empiric Treatment (Upon Clinical Suspicion)

Start antibiotics immediately based on clinical features alone—do not wait for laboratory confirmation. 1, 2, 4

Antibiotic Selection by Disease Severity

Early Mild Disease:

• Penicillin or tetracycline antibiotics during bacteremic phase 1, 2
• Doxycycline is effective for early treatment 4

Severe Disease (Weil's Disease with Jaundice):

• Immediate antibiotic therapy plus intensive supportive care 2
• Streptomycin shows best bactericidal action; gentamicin, tobramycin, and isepamicin are effective alternatives 3
• Penicillins, cephems, tetracyclines require long-term therapy with large doses from early stage until antibody appearance 3
• May require renal or liver support despite therapy 1, 2

Critical Treatment Caveat

A systematic review showed no benefit for antibiotics in established severe leptospirosis based on three trials, as severe disease is probably immunologically mediated; however, most infectious disease specialists continue recommending antibiotics pending further evidence. 1

Critical Pitfalls to Avoid

• Delaying treatment while awaiting laboratory confirmation leads to life-threatening complications 2
• Assuming mild symptoms will remain mild is dangerous—even with treatment, patients with severe disease can become critically ill 2
• Underestimating disease severity based on modest transaminase elevations (typically <2000 IU/L) compared to other causes of acute liver failure 1
• Missing the diagnosis by not recognizing the characteristic combination of fever, raised right hemi-diaphragm on chest X-ray, and exposure history 1
• Failing to monitor for Jarisch-Herxheimer reaction within 24 hours of antibiotic initiation, which can cause chills, fever, hypotension, and impaired consciousness requiring ICU admission and vasopressor support 6