• Clinical science

Leptospirosis (Mud fever…)

Summary

Leptospirosis is a zoonotic disease caused by gram-negative Leptospira bacteria. Direct transmission to humans occurs when broken skin and mucous membranes come into contact with the urine of infected animals such as rodents. The early phase of the disease is mild and characterized by nonspecific symptoms (e.g., fever, headache, and myalgia). In most cases, symptoms resolve spontaneously after a week. However, in 10% of cases, the disease progresses rapidly to a severe form (icterohemorrhagic leptospirosis, or Weil disease), which typically presents with a triad of jaundice, bleeding manifestations, and acute kidney injury. Diagnosis is based on patient history, clinical findings, and laboratory tests. Treatment consists of antibiotics and supportive care.

Epidemiology

  • Leptospirosis is the most common zoonotic disease worldwide and is most common in the tropics
  • Low incidence in the US (100–200 cases per year): Half of these cases are reported in Hawaii.

Epidemiological data refers to the US, unless otherwise specified.

Etiology

  • Pathogen: Leptospira(especially L. interrogans); , a genus of gram-negative spirochete with hook-shaped ends
  • Route of infection
    • Contact with soil, food, and/or water contaminated with the urine of infected animals (most commonly rodents ) → entry of Leptospira through skin/mucous membrane lesions
    • Occupational groups at risk
      • Farmers, sewer workers
      • Water sports enthusiasts (e.g., surfers) may also be affected

Clinical features

The incubation time is 2–30 days. The disease has a mild form, which is characterized by nonspecific symptoms that generally resolve spontaneously after a week. In 10% of cases, the disease progresses rapidly to a severe form (icterohemorrhagic leptospirosis, or Weil disease). [1][2]

Mild (anicteric) leptospirosis [3]

Clinical manifestations during the early phase are due to bacteremia.

Most cases of mild leptospirosis resolve spontaneously. Only 10% of patients with mild leptospirosis progress to the severe form (Weil disease).

Severe leptospirosis (Weil disease, icterohemorrhagic leptospirosis) [3]

Clinical features are due to systemic spread and multiorgan involvement.

Severe leptospirosis is associated with a high mortality rate.

Diagnostics

Treatment

If leptospirosis is suspected based on a patient's clinical features and history, empiric therapy should be started right away.

Prevention