Leptospirosis

Key Features

Essentials of Diagnosis

• Biphasic course lasting 2–3 weeks

• Initial phase: high fever, headache, myalgia, and conjunctivitis

• Apparent recovery for 2–3 days

• Return of fever associated with meningitis

• Jaundice, hemorrhages, and renal insufficiency (severe cases)

• Positive leptospiral agglutination test

General Considerations

• Caused by many antigenically distinct but morphologically similar spirochetes

• Organism enters through the skin or respiratory tract

• Classically the severe form (Weil disease), with jaundice and a high mortality rate, was associated with infection with Leptospira icterohaemorrhagiae after immersion in water contaminated with rat urine

• A variety of animals (eg, dogs, rats, and cattle) may serve as reservoirs for pathogenic Leptospira and that severe disease may be caused by many different serogroups.

Demographics

• Sewer workers, farmers, slaughterhouse workers, animal handlers, and soldiers are at risk for occupational exposure

• Outbreaks have resulted from swimming in contaminated streams and harvesting field crops

• In the United States, about 100 cases are reported yearly, about one-third of them in children

Clinical Findings

Symptoms and Signs

• Initial phase

  • Incubation period is 4–19 days (mean, 10 days)

  • Chills, fever, headache, myalgia (especially lumbar area and calves), conjunctivitis without exudate, photophobia, cervical lymphadenopathy, and pharyngitis commonly occur

  • Lasts for 3–7 days

• Phase of apparent recovery: Symptoms typically (but not always) subside for 2–3 days

• Systemic phase

  • Fever reappears and is associated with headache, muscular pain, and tenderness in the abdomen and back, and nausea and vomiting

  • Conjunctivitis and uveitis are common

  • Lung, heart, and joint involvement occasionally occur

  • Severe headache and mild nuchal rigidity are usual, but delirium, coma, and focal neurologic signs may be seen

  • Kidney or liver affected in about 50% of cases

  • Gross hematuria and oliguria or anuria is sometimes seen

  • Jaundice may be associated with an enlarged and tender liver

  • Acalculous cholecystitis occurs

  • Petechiae, ecchymoses, and gastrointestinal bleeding may be severe

  • Rash is seen in 10–30% of cases

    • May be maculopapular and generalized or petechial or purpuric

    • Erythema nodosum is seen occasionally

    • Peripheral desquamation may occur

    • Gangrenous areas are sometimes noted over the distal extremities

Differential Diagnosis

• During the prodrome, malaria, typhoid fever, typhus, rheumatoid arthritis, brucellosis, and influenza may be suspected

• Later, a variety of other diseases need to be distinguished, including encephalitis, viral or tuberculous meningitis, viral hepatitis, glomerulonephritis, viral or bacterial pneumonia, rheumatic fever, subacute infective endocarditis, acute surgical abdomen, and Kawasaki disease

Diagnosis

Laboratory Findings

• Leptospires are present in the blood and CSF only during the first 10 days of illness

• CSF shows moderate pleocytosis (< 500/μL), predominantly mononuclear cells, increased protein (50–100 mg/dL), and normal glucose

• Leptospires appear in the urine during the second week, where they may persist for 30 days or ...