Obligate aerobic spirochete bacteria in the genus Leptospira.
Infection occurs through abrasions or cuts in the skin, or through the conjunctiva and mucous membranes. Humans may be infected by direct contact with urine or reproductive fluids from infected animals, or with water or soil contaminated with those fluids. Prolonged immersion in contaminated water increases the risk for infection. Infection rarely occurs through animal bites or human-to-human contact.
Leptospirosis has worldwide distribution, with a higher incidence in tropical climates, especially after heavy rainfall or flooding due to hurricanes. Outbreaks of leptospirosis have occurred in the United States after flooding in Hawaii and Puerto Rico. Travelers participating in recreational water activities are at increased risk, particularly after heavy rainfall or flooding.
The incubation period is 2 days to 3 weeks. The acute phase (approximately 7 days) presents as an acute febrile illness with symptoms including headache (can be severe and include retroorbital pain and photophobia), fever, chills, myalgia, nausea, diarrhea, abdominal pain, uveitis, conjunctival suffusion, and occasionally, a skin rash. The second or immune phase is characterized by antibody production and the presence of leptospires in the urine. The icteric or severe form of the disease (Weil disease) occurs in 5%–10% of patients with leptospirosis. Symptoms include jaundice, renal failure, hemorrhage (especially pulmonary), cardiac arrhythmias, pneumonitis, and hemodynamic collapse.
Diagnosis of leptospirosis is usually based on clinical recognition and serology; microscopic agglutination test is the gold standard. Culture is relatively insensitive, but detection of the organism using real-time PCR can provide a more timely diagnosis.
Doxycycline is effective in decreasing the severity and duration of leptospirosis and should be initiated early in the course of the disease if leptospirosis is suspected. Intravenous penicillin is a drug of choice for patients with severe leptospirosis. Patients with severe leptospirosis may require hospitalization, supportive therapy, and close monitoring.
No vaccine is available in the United States. Travelers who might be at an increased risk for infection should be advised to consider preventive measures such as chemoprophylaxis, wearing protective clothing, especially footwear, and covering cuts and abrasions with occlusive dressings. Until further data become available, CDC recommends chemoprophylaxis with doxycycline (200 mg orally, weekly), begun 1–2 days before and continuing through the period of exposure for people at high risk of leptospirosis. Doxycycline is not recommended for pregnant women or children aged <8 years.
Bajani MD, Ashford DA, Bragg SL, Woods CW, Aye T, Spiegel RA, et al. Evaluation of four commercially available rapid serologic tests for diagnosis of leptospirosis. J Clin Microbiol. 2003 Feb;41(2):803–9.
Haake DA, Dundoo M, Cader R, Kubak BM, Hartskeerl RA, Sejvar JJ, et al. Leptospirosis, water sports, and chemoprophylaxis. Clin Infect Dis. 2002 May 1;34(9):e40–3.