What are the diagnosis, treatment, and clinical features of leptospirosis?

Leptospirosis: Diagnosis, Clinical Features, and Treatment

Clinical Features

Leptospirosis presents as a biphasic illness with two distinct clinical forms: a mild-to-moderate flu-like syndrome (most common) and severe disease with jaundice, hemorrhage, and hepato-renal failure (Weil's disease, occurring in 5-10% of cases). 1

Septicemic/Bacteremic Phase (Days 1-7)

• High fever (typically ≥39°C) 1
• Severe diffuse myalgias, particularly in the calves 1
• Headache 1
• Conjunctival suffusion (a highly suggestive sign that should immediately raise suspicion) 1, 2
• Cough and respiratory symptoms may indicate pulmonary involvement 1

Immune Phase (After Day 7)

• Fever recurrence 2
• Severe muscle pain 2
• Potential organ failure 2
• Aseptic meningitis (occurs in ~19% of cases) 1
• Cardiac involvement (myocarditis/pericarditis, independently predictive of severe disease) 1

Severe Disease (Weil's Disease)

• Jaundice 1
• Hemorrhage 1
• Hepato-renal failure 1
• Pulmonary involvement (20-70% of patients, with severe manifestations being rare) 3

Critical Exposure History

High-risk exposures include: 1

• Recreational water sports in fresh water
• Occupational exposure to animals or contaminated water
• Recent flooding with water contact
• Contact with rats, dogs, cattle, or other domestic/wild animals

Diagnosis

Clinical Suspicion

Diagnosis should be suspected based on the triad of fever with chills, diffuse myalgias, and conjunctival suffusion in a patient with appropriate exposure history. 1, 2

Laboratory Findings (Non-Specific)

• Proteinuria and hematuria on urinalysis 1
• Leukocytosis with polymorphonuclear predominance 1
• Elevated bilirubin with mild transaminase elevation (distinguishes from viral hepatitis) 1
• Anemia if significant hemorrhage present 1
• Alterations in renal function tests 1

Confirmatory Testing

Serology is the most common confirmatory method, but results come too late for early treatment decisions. 1, 2

Serologic Testing:

• IgM titers >1:320 are suggestive of leptospirosis 1
• IgM titers 1:80-1:160 consistent with early infection 1
• Convalescent serology (>10 days after symptom onset) confirms diagnosis 1
• Earliest positive results occur 6-10 days after symptom onset 2

Blood Cultures:

• Must be obtained within the first 5 days of illness, before antibiotics 1, 2
• Three or more blood cultures should be taken at least 1 hour apart 4

Molecular Testing:

• Nucleic acid amplification testing (NAAT) provides 1-2 hour turnaround time 1

Critical Diagnostic Pitfall

Never delay treatment while awaiting laboratory confirmation—leptospirosis can rapidly progress to life-threatening complications, and initial investigations are non-specific. 2

Treatment

Mild-to-Moderate Disease

Treatment should be started immediately upon clinical suspicion with oral doxycycline or penicillin. 1, 2

Antibiotic Regimen:

• Doxycycline 100 mg orally twice daily for 7 days 5, 6
• Alternative: Penicillin or amoxicillin 1
• Doxycycline reduces illness duration by 2 days and favorably affects fever, malaise, headache, and myalgias 5
• Treatment prevents leptospiruria 5

Hospitalization Criteria:

• Hospitalize patients with moderate leptospirosis showing systemic signs of infection, even without criteria for severe disease 1

Severe Disease (Weil's Disease)

Immediate antibiotic therapy must be initiated within 1 hour of recognition, without waiting for laboratory confirmation—each hour of delay increases mortality. 1, 2

Antibiotic Regimen:

• Intravenous penicillin (traditional drug of choice) 6
• Ceftriaxone (now challenging penicillin as preferred agent due to easier administration) 6
• Standard course: 7 days, extended to 10 days if slow clinical response 1
• Reassess antimicrobial regimen daily for potential de-escalation 1

Critical Management Points:

• Obtain blood cultures before antibiotics if this causes no significant delay (<45 minutes) 1
• Consider source control measures within 12 hours if applicable 1
• Never discontinue antibiotics early—complete the full course even with clinical improvement 1
• Treatment initiated after 4 days of symptoms may be less effective 1

Supportive Care for Severe Disease

Fluid Resuscitation:

• Target systolic blood pressure >90 mmHg in adults 1
• Target normal heart rate and blood pressure in children 1
• Monitor for crepitations indicating fluid overload or impaired cardiac function 1
• Continuous observation with frequent clinical examinations required 1

ICU Admission Criteria:

• Persistent or worsening tissue hypoperfusion despite initial fluid resuscitation 1
• Potential need for renal and liver support 2

Prophylaxis (Post-Flood Exposure)

Prophylaxis should be reserved for settings where attack rates exceed 10 cases per 100 person-years, particularly in endemic areas with documented high attack rates. 2

Prophylaxis Regimen:

• Doxycycline (dose not specified in guidelines for prophylaxis) 2
• Contraindicated in children under 8 years due to permanent tooth discoloration and enamel hypoplasia 2
• No established alternative prophylaxis for young children 2

Critical Treatment Pitfalls to Avoid

• Never delay treatment while awaiting laboratory confirmation 2
• Never assume mild symptoms will remain mild—even with treatment, patients can become critically ill 2
• Never use doxycycline prophylaxis in children under 8 years 2
• Never ignore occupational or recreational water exposure history in endemic areas 2
• Never mistake leptospirosis for viral hepatitis in patients with fever and jaundice (leptospirosis shows elevated bilirubin with only mild transaminase elevation) 1