What are the diagnosis and management options for a patient suspected of having leptospirosis, including differential diagnosis and treatment considerations?

Leptospirosis: Diagnosis and Management

Immediate Clinical Action

Start antibiotic treatment immediately upon clinical suspicion of leptospirosis without waiting for laboratory confirmation, as each hour of delay increases mortality. 1, 2

Diagnosis

Key Historical Features to Elicit

• Exposure history within 2-20 days including contact with flood water, contaminated fresh water, recreational water sports, occupational exposure to animals (rats, cattle, pigs, dogs), or recent flooding 1, 2, 3
• Biphasic illness pattern: initial bacteremic phase (4-7 days) with high fever (≥39°C), severe myalgias (especially calves), and headache 1, 2
• High-risk occupations: agricultural workers in flooded fields, sewage workers, animal caretakers, water sports participants 3, 4

Critical Physical Examination Findings

• Conjunctival suffusion (highly suggestive and pathognomonic finding) 1, 2
• Jaundice (indicates severe disease/Weil's disease) 1, 2
• Signs of hemorrhage (petechiae, ecchymoses, hemoptysis) 2, 5
• Hepatomegaly 1
• Respiratory distress or hypoxemia 1

Laboratory Workup (Obtain Within First Hour)

Initial tests (before antibiotics if no significant delay <45 minutes): 1, 2

• Blood cultures (ideally within first 5 days of illness, before antibiotics) 2, 6
• Complete blood count (look for leukocytosis, thrombocytopenia, anemia if hemorrhage) 1, 2
• Comprehensive metabolic panel (elevated bilirubin with mild transaminase elevation, renal dysfunction) 1, 2
• Urinalysis (proteinuria and hematuria) 1, 2
• Serum lactate 7
• Serum amylase 7

Diagnostic confirmation tests: 1, 2

• IgM ELISA: Titer >1:320 is diagnostic; 1:80-1:160 suggests early infection 1, 2
• Convalescent serology (MAT): Repeat >10 days after symptom onset; fourfold increase in titer confirms diagnosis 1, 2
• PCR/NAAT: Highly sensitive and specific, especially in first few days before antibody development; turnaround time 1-2 hours 1, 6

Critical pitfall: Do not wait for serological confirmation before starting antibiotics, as serology is often negative in the first week 1

Predictors of Severe Disease

Laboratory findings associated with poor prognosis: 7

• Platelet count ≤50,000/µL
• Serum creatinine >200 mM
• Serum lactate >2.5 mM
• Serum amylase >250 UI/L
• Leptospiremia >1000 leptospires/mL by qPCR

Clinical risk factors for severity: 7

• Current cigarette smoking
• Delay >2 days between symptom onset and antibiotic initiation
• Infection with Leptospira interrogans serogroup Icterohaemorrhagiae

Treatment

Mild to Moderate Disease (Outpatient or Hospitalization Without Severe Criteria)

Doxycycline 100 mg orally twice daily for 7 days is the treatment of choice 1, 2

Alternative oral antibiotics (if doxycycline unavailable): 1

• Amoxicillin
• Tetracycline

Clinical monitoring: 1

• Expect clinical improvement within 3 days of antibiotic initiation
• Follow-up 2 days after first visit for seriously ill patients
• Return if symptoms persist >3 weeks

Severe Disease (Weil's Disease, Septic Shock, Organ Dysfunction)

Antibiotic regimens (start within 1 hour of recognition): 1, 2

• Ceftriaxone 2g IV daily for 7 days (preferred) 1
• Penicillin G 1.5 million units IV every 6 hours for 7 days (alternative) 1
• Extend to 10 days if slow clinical response 2

Supportive care measures: 1, 2

• Aggressive IV fluid resuscitation: Isotonic crystalloid or colloid up to 60 ml/kg as three boluses of 20 ml/kg, reassessing after each bolus 1
• Target systolic BP >90 mmHg in adults, normal heart rate and BP in children 2
• Monitor for crepitations indicating fluid overload or impaired cardiac function 2
• ICU admission if persistent hypoperfusion despite initial fluid resuscitation, repeated fluid boluses needed, or signs of circulatory failure 1, 2
• Methylprednisolone 0.5-1.0 mg/kg IV daily for 1-2 weeks for respiratory complications 1
• Urinary catheter for monitoring urine output (target >0.5 ml/kg/hour) 8

Critical pitfall: Do not discontinue antibiotics early despite clinical improvement; complete the full 7-10 day course 1, 2

Special Populations

Children <8 years: 1

• Avoid doxycycline due to permanent tooth discoloration risk
• Use penicillin or ceftriaxone instead

Pregnant women: 1

• Avoid tetracyclines and azoles
• Use penicillin or ceftriaxone

Post-flood exposure prophylaxis: 1

• Doxycycline 200 mg single dose orally provides 76.8% protection
• Reserve for high-risk settings only

Differential Diagnosis

When evaluating suspected leptospirosis, consider these alternative diagnoses based on clinical presentation: 8, 2, 5

Fever with jaundice: 2

• Viral hepatitis (most commonly confused with leptospirosis)
• Malaria
• Yellow fever
• Dengue hemorrhagic fever

Acute febrile illness with myalgias: 4, 5

• Influenza
• Dengue fever
• Hantavirus
• Rickettsial diseases

Fever with renal failure: 5

• Hemolytic uremic syndrome
• Acute interstitial nephritis
• Other causes of acute kidney injury

Fever with pulmonary hemorrhage: 5

• Goodpasture syndrome
• Granulomatosis with polyangiitis
• Hantavirus pulmonary syndrome

Aseptic meningitis (occurs in ~19% of leptospirosis cases): 2

• Viral meningitis
• Tuberculous meningitis
• Fungal meningitis

Key distinguishing feature: Conjunctival suffusion is highly suggestive of leptospirosis and helps differentiate it from other causes of acute febrile illness 1, 2