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Chapter 3Infectious Diseases Related To Travel
Leptospirosis
Robyn Stoddard, Sean V. Shadomy
INFECTIOUS AGENT
Leptospirosis is caused by obligate aerobic spirochete bacteria in the genus Leptospira, which grow optimally at 28°C–30°C.
MODE OF TRANSMISSION
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.
EPIDEMIOLOGY
Leptospirosis has worldwide distribution, with a higher incidence in tropical climates. Domestic, peridomestic, and wild animals are maintenance hosts of the bacteria and excrete the bacteria in their urine, amniotic fluid, or placental tissue, which can contaminate the soil and water. Most Leptospira species can persist 2–3 weeks in fresh water, damp soil, or mud. Flooding after hurricanes or heavy rainfall facilitates the spread of the organism, contributing to outbreaks. This is especially true in regions with high endemic rates of infection. Leptospirosis is associated with animal husbandry.
Rodentborne leptospirosis may be a risk to people exposed to rat urine in infested urban areas. Travelers participating in recreational water activities, such as whitewater rafting, adventure racing, kayaking, or triathlon events may be at increased risk for leptospirosis, particularly after heavy rainfall or flooding. Outbreaks of leptospirosis have occurred in the United States after flooding in Hawaii and Puerto Rico. Leptospirosis has also been reported in international travelers to regions experiencing epidemics after heavy rainfall or flooding.
CLINICAL PRESENTATION
The incubation period is 2 days to 3 weeks. The symptoms of leptospirosis are varied and often biphasic. The acute or bacteremic phase lasts a week, followed by the immune phase that is characterized by antibody production and the presence of leptospires in the urine. The acute, generalized illness mimics other acute febrile illnesses, such as dengue fever, malaria, or typhus. Common symptoms include headache, fever, chills, myalgia, nausea, diarrhea, abdominal pain, uveitis, adenopathy, conjunctival suffusion without purulent discharge, and occasionally, a skin rash. The headache is often severe and includes retroorbital pain and photophobia. Aseptic meningitis occurs in up to 25% of cases.
The icteric or severe form of the disease (Weil disease) occurs in 5%–10% of patients with leptospirosis. Symptoms include jaundice, renal failure, hemorrhage, cardiac arrhythmias, pneumonitis, and hemodynamic collapse. The death rate in patients with severe leptospirosis is 5%–15%.
DIAGNOSIS
Diagnosis of leptospirosis is usually based on serology. Antibodies may be detected in the blood within 5–7 days of symptom onset. Culture and demonstration of the organism under darkfield microscopy are both relatively insensitive. No PCR assay has been validated with clinical specimens. Confirmation of leptospirosis requires seroconversion between acute- and convalescent-phase serum specimens, as demonstrated by the microscopic agglutination test (MAT), culture of the organism from clinical specimens, or demonstration of Leptospira in a clinical specimen by immunofluorescence.
MAT, the recognized standard reference test for serologic diagnosis of leptospirosis, is performed only in reference laboratories. Although MAT is not specific for diagnosis of acute cases, a single elevated MAT titer in a patient with a compatible febrile illness and suspected exposure suggests acute leptospirosis. Seroconversion with a 4-fold or larger rise in titer between acute- and convalescent-phase serum specimens obtained 2 weeks or more apart confirms the diagnosis.
Several rapid, reliable serologic assays are commercially available for diagnostic screening for an acute infection. A recent evaluation of 4 of these assays concluded that both a microplate IgM ELISA and an IgM dot-ELISA dipstick test exhibited high sensitivity and specificity on acute-phase samples.
TREATMENT
Missed or delayed diagnosis of leptospirosis is common because of its nonspecific clinical presentation and a low index of suspicion among clinicians seeing returned travelers. Antimicrobial therapy 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. As with other spirochete infections, a Jarisch-Herxheimer reaction (an acute febrile reaction that can range from rash to anaphylaxis) can develop after initiation of penicillin therapy. Various methods have been described to prevent or control Jarisch-Herxheimer reactions, and management should follow the appropriate standards for patient care. Doxycycline is effective in decreasing the severity and duration of leptospirosis and the occurrence of leptospiruria. Parenteral third-generation cephalosporins and azithromycin may also be used for treatment. Because of the risk for potential complications, including cardiac arrhythmia, renal failure, pulmonary involvement and respiratory distress, or myocarditis, patients with leptospirosis may require hospitalization, supportive therapy, and close monitoring.
PREVENTIVE MEASURES FOR TRAVELERS
No vaccine is available in the United States. Travelers who might be at an increased risk for infection because of recreational water activities or exposure to contaminated surface waters and soil should be advised to consider preventive measures such as wearing protective clothing, especially footwear, and covering cuts and abrasions with occlusive dressings. They should avoid contact with, submersion in, or swallowing potentially contaminated water.
Travelers at risk because of destination or activities during travel may benefit from chemoprophylaxis. Until further data become available, CDC recommends that adult travelers who might be at increased risk for leptospirosis be advised to consider chemoprophylaxis with doxycycline (200 mg orally, weekly), begun 1–2 days before and continuing through the period of exposure. Indications for prophylactic doxycycline use for children have not been established. Travelers at increased risk for leptospirosis and in need of malaria chemoprophylaxis should consider using doxycycline for both indications.
BIBLIOGRAPHY
- 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.
- Gaynor K, Katz AR, Park SY, Nakata M, Clark TA, Effler PV. Leptospirosis on Oahu: an outbreak associated with flooding of a university campus. Am J Trop Med Hyg. 2007 May;76(5):882–5.
- Griffith ME, Hospenthal DR, Murray CK. Antimicrobial therapy of leptospirosis. Curr Opin Infect Dis. 2006 Dec;19(6):533–7.
- Guidugli F, Castro AA, Atallah AN. Antibiotics for preventing leptospirosis. Cochrane Database Syst Rev. 2000(4):CD001305.
- 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.
- Levett PN. Leptospirosis. Clin Microbiol Rev. 2001 Apr;14(2):296–326.
- Morgan J, Bornstein SL, Karpati AM, Bruce M, Bolin CA, Austin CC, et al. Outbreak of leptospirosis among triathlon participants and community residents in Springfield, Illinois, 1998. Clin Infect Dis. 2002 Jun 15;34(12):1593–9.
- Pappas G, Cascio A. Optimal treatment of leptospirosis: queries and projections. Int J Antimicrob Agents. 2006 Dec;28(6):491–6.
- Phimda K, Hoontrakul S, Suttinont C, Chareonwat S, Losuwanaluk K, Chueasuwanchai S, et al. Doxycycline versus azithromycin for treatment of leptospirosis and scrub typhus. Antimicrob Agents Chemother. 2007 Sep;51(9):3259–63.
- Sanders EJ, Rigau-Perez JG, Smits HL, Deseda CC, Vorndam VA, Aye T, et al. Increase of leptospirosis in dengue-negative patients after a hurricane in Puerto Rico in 1966. Am J Trop Med Hyg. 1999 Sep;61(3):399–404.
- Vinetz JM, Glass GE, Flexner CE, Mueller P, Kaslow DC. Sporadic urban leptospirosis. Ann Intern Med. 1996 Nov 15;125(10):794–8.
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