Clinical Overview of Leptospirosis

Overview

The Leptospira bacterium that causes leptospirosis spreads through the urine of infected livestock, pets, rodents, marine mammals, and wild animals. If the urine from an infected animal has contaminated a water source or soil, the bacterial can persist for several weeks to months.

In people, leptospirosis can cause a wide range of non-specific symptoms and can be confused with other differential diagnoses. Some people who are infected may be asymptomatic.

People can lower their risk of getting leptospirosis by not drinking, bathing, swimming in, or wading in water that might be contaminated with animal urine, especially after hurricanes or floods. They should also avoid contact with animals that may be infected.

Cause

Leptospires are the bacteria that cause leptospirosis. They:

• Are long, thin, motile spirochetes.
• Spread in the urine and body fluids of infected animals.
• Survive for weeks to months in fresh water and wet soil in warm areas.

Leptospires are classified into more than 300 pathogenic serovars based on antigenic properties, although antigenic properties are not a predictor of species designation. The serovars and species can vary by region. Leptospirosis occurs worldwide, and it's more common in temperate or tropical climates.

Testing and diagnosis

Leptospirosis is diagnosed by detecting Leptospira DNA from blood, serum, urine, or cerebrospinal fluid (if neurologic signs present), or by detecting an antibody response to the bacteria. Choosing the right test depends on how long a person has had clinical signs or symptoms consistent with leptospirosis. CDC does not recommend testing asymptomatic people.

Signs and symptoms

The incubation period of leptospirosis is 5-14 days with a range of 2-30 days. The disease presents like many other conditions and has a wide range of non-specific symptoms:

• Fever
• Muscle aches
• Headache
• Vomiting
• Nausea
• Jaundice
• Diarrhea
• Chills
• Abdominal pain
• Fatigue
• Conjunctival suffusion
• Sometimes rash

Untreated patients could develop kidney failure, jaundice, respiratory distress or failure, liver failure, and meningitis. In 5-10% of cases, multiorgan failure and death can occur.

Post-exposure prophylaxis

There are limited data supporting the effectiveness of PEP in preventing leptospirosis and risks for antimicrobial drug resistance associated with widespread use of antibiotics.

If a person has contact with an animal known or suspected to have leptospirosis and is asymptomatic, CDC does not have standard antimicrobial post-exposure prophylaxis (PEP) recommendations. The decision to pursue PEP by patients and their healthcare providers should be done on a case-by-case basis.

Treatment

Early treatment may decrease the severity and duration of disease. For patients with a high clinical suspicion of leptospirosis, start antibiotic treatment as soon as possible without waiting for laboratory results.

Mild symptoms

Doxycycline is the drug of choice (100 mg orally, twice daily for 7 days), if not contraindicated.

Other options include:

• Azithromycin (500 mg orally, once daily for 3 days)
• Ampicillin (500-750 mg orally, every 6 hours for 7 days)
• Amoxicillin (500 mg orally, every 6 hours for 7 days).

Severe disease

• IV penicillin is the drug of choice (1.5 million units IV, every 6 hours), OR
• Ceftriaxone (1 g IV, every 24 hours)

Disease trends

• Leptospirosis is among the leading zoonotic disease causes of illness worldwide. The disease is underdiagnosed and underreported, so true numbers are likely higher.
• An estimated 1 million cases occur globally each year, resulting in nearly 60,000 deaths.
• It occurs most frequently in tropical and subtropical climates.
• Leptospirosis has been reported throughout the United States from many states and jurisdictions.
• Cases of leptospirosis can increase after hurricanes or flooding when people may have to wade through contaminated water or use it for drinking or bathing.
  

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