II. Epidemiology
- Worldwide: Common
- United States: 100-200/year (underestimated)
- Hawaii accounts for 50% of cases
III. Pathophysiology
- Fresh-waterborne Spirochete (Leptospira interrogans, Leptospira biflexa and 14 other species)
- Transmission
- Passed via infected animals urine
- Rats (most common)
- Livestock (e.g. horses, cattle, sheeps, goats)
- Dogs (often asymptomatic)
- Leptospira remains viable for months in water and soil (esp. tropical and subtropical climates)
- Penetrates mucus membranes, broken skin, Conjunctiva
- Passed via infected animals urine
- Incubation: 2 to 30 days
- Mechanism of injury
- Small vessel injury (Vasculitis)
IV. Risk Factors
- Water activity in endemic areas (Hawaii, Malaysia)
- Fresh-water related activities (contaminated water or soil exposure)
- Farming or gardening
- Hiking across streams
- Swimming
- Rafting
- Canoeing
- Spelunking
- Camping
- Occupations
- Veterinary workers
- Agriculture
- Sewage workers
- Fishing industry
- Flood exposure
V. Findings: Symptoms and signs
- Follows 7-12 day incubation
- Anicteric Leptospirosis (90% of cases)
- Phase 1: Initial septicemic phase (lasts 3-7 days)
- Headache
- High fever
- Myalgia
- Calf tenderness
- Conjunctivitis
- Maculopapular rash
- Phase 2 (follows brief improvement from phase 1)
- Aseptic Meningitis
- Uveitis
- Chorioretinitis
- Hematuria
- Hepatomegaly
- Splenomegaly
- Conjunctival injection
- Phase 1: Initial septicemic phase (lasts 3-7 days)
- Icteric Leptospirosis (Weil's Syndrome, 10% of symptomatic cases, 5-15% mortality)
- Much more severe than anicteric form
- Fever
- Jaundice
- Azotemia
- Hypotension
- Hemorrhagic Vasculitis
- Disseminated Intravascular Coagulation (DIC)
VI. Labs
- Start empiric therapy if Leptospirosis suspected
- Do not wait for diagnostic tests
-
Serology
- Acute phase serum 1-2 weeks after illness onset
- Convalesent serum 3-4 weeks after illness onset
- Culture (Growth may require 16 weeks)
- Dark field microscopy
- Best Test Sensitivity is flow blood or CSF within the first 7-10 days
- After 7 days, urine is best sample
VII. Management
- Consider empirical treatment if suspected
- Mild to moderate infection
- Doxycycline 100 mg orally twice daily for 7 days (if age >8 years old) OR
- Amoxicillin 16 mg/kg up to 500 mg orally three times daily for 7 days OR
- Azithromycin 10 mg/kg up to 1 g on day 1, then 5 mg/kg up to 500 mg daily for 2 days
- Severe infection (hospitalized)
- Penicillin G 100,000 units/kg up to 1.5 MU IV every 6 hours for 7 days or
- Ceftriaxone 100 mg/kg up to 2 g IV every 24 hours for 7 days
- Alternatively IV Doxycycline may be used if age >8 years old
VIII. Complications
- Meningitis
- Hepatitis to Liver Failure
- Nephritis to Renal Failure
IX. Prevention
- Doxyxycline 200 mg once weekly for prophylaxis if high risk of exposure
- Infected pet quarantine
- Avoid contact with urine of infected pet and disinfect contaminated areas (with household cleaners)
- Infected dogs should be walked to urinate away from water bodies and from human frequented areas
- Other measures
- Consider Vaccination of dog (covers 4 most common Leptospira species)
- Keep dogs away from standing water
X. References
- (2016) Sanford Guide to Antibiotics, IOS App accessed 4/14/2016
- Anderson (2014) Crit Dec Emerg Med 28(7): 11-9
- Tappero in Mandell (2000) Infectious Disease p. 2495
- Day (2016) Am Fam Physician 94(10): 794-802 [PubMed]
- Joyce (2002) Prim Care 29(4):971-81 [PubMed]
- Lo Re (2003) Am Fam Physician 68(7):1343-50 [PubMed]
- Perkins (2017) Am Fam Physician 95(9):554-60 [PubMed]