Brief description

Credits:  O. Chávez

Leptospirosis is a zoonotic disease with epidemic potential, especially after a heavy rainfall, caused by a bacterium called Leptospira. Leptospira interrogans is pathogenic to humans and animals, with more than 200 serologic variants or serovars. Humans usually acquire leptospirosis through direct contact with the urine of infected animals or a urine-contaminated environment. Human-to-human transmission occurs only very rarely. Leptospirosis may present with a wide variety of clinical manifestations, from a mild illness that may progress to a serious and sometimes fatal disease. Its symptoms may mimic many diseases, such as influenza, dengue and other viral haemorrhagic diseases; making the correct diagnosis (clinical and laboratory) at the onset of symptoms is important to prevent severe cases and save lives, primarily in outbreak situations.

:: Reference WHO (pages V; 1-3; 47-50)

Epidemiological situation

Credits: PAHO

Leptospirosis occurs worldwide but is endemic mainly in countries with humid subtropical and tropical climates. Estimates indicate that there are more than 500,000 cases of leptospirosis each year worldwide. Leptospirosis is a disease of epidemic potential, especially after heavy rainfall or flooding. Cases have been reported in most countries of the Americas and outbreaks have been reported in Brazil, Nicaragua, Guyana and several other Latin American countries. The majority of reported cases have severe manifestations, for which mortality is greater than 10%. The number of human cases is not known precisely due to under- or misdiagnosis. Outbreaks can be associated with floods and hurricanes. Leptospirosis can also be an occupational hazard for people who work outdoors or with animals, such as rice and sugar-cane field workers, farmers, sewer workers, veterinarians, dairy workers, and military personnel. It is also a recreational hazard to those who swim or wade in contaminated water. Leptospirosis is a problem of human and veterinary public health. The numerous Leptospira strains can establish infections within a variety of animal hosts that includes rodents, livestock, and other domestic animals while humans serve as incidental hosts. Wild and domestic animals in the carrier state may shed leptospires intermittently for many years or even a lifetime.

:: Reference WHO (pages 21-22; 37; 81); WHO (a) (pages 9-11); FAO (pages 30-34; in Spanish)

Leptospirosis in humans

• Clinical Diagnosis:
  
  
•  Typically, the disease presents in four broad clinical categories:
1. A mild, influenza-like illness;
2. Weil's syndrome characterized by jaundice, renal failure, haemorrhage and myocarditis with arrhythmias
3. Meningitis/meningoencephalitis
4. Pulmonary haemorrhage with respiratory failure
• Of the many symptoms the most common clinical features of leptospirosis include fever, headache, myalgia (particularly in the calf muscle), conjunctival suffusion, jaundice, general malaise in addition to other symptoms/signs
• Incubation period: 5-14 days, with a range of 2-30 days
• Symptoms are easily confused with other common diseases in the tropics, such as dengue and other hemorrhagic fevers
• The diagnosis of leptospirosis should be considered in any patient presenting with an abrupt onset of fever, chills, conjunctival suffusion, headache, myalgia and jaundice
• History of occupational or recreational exposure to infected animals or to an environment potentially contaminated with animal urine

:: Reference WHO (pages 5-8; 47-50)

• Differential diagnosis

Credits: O. Chávez

The following diseases should be considered in the differential diagnosis of leptospirosis: influenza, dengue and dengue hemorrhagic fever, hanta virus infection, yellow fever and other viral hemorrhagic fevers, rickettsiosis, borreliosis, brucellosis, malaria, pyelonephritis, aseptic meningitis, chemical poisoning, food poisoning, typhoid fever and other enteric fevers, viral hepatitis, pyrexia of unknown origin, primary HIV seroconversion, legionnaire’s disease, toxoplasmosis, infectious mononucleosis, pharyngitis.

:: Reference: WHO (page 47)

• Laboratory testing for confirmation::

Diagnosis is usually based on serology in conjunction with the clinical presentation and epidemiological data (a history of possible exposure, presence of risk factors). The microscopic agglutination test (MAT) and the enzyme linked immunosorbent assay (ELISA) are two serologic tests used for laboratory diagnosis of leptospirosis. In order to obtain a positive diagnosis using the gold standard MAT, a minimum of two serum samples taken at intervals of about 10 days apart, must be compared to observe a four-fold or greater rise in antibody titer. Isolation of leptospires from blood, urine or other clinical materials can be achieved through culture, and detection by polymerase chain reaction (PCR) and immuno staining techniques may be available in some centers. Isolation of leptospires is the only direct and definitive proof of infection. For postmortem diagnosis, in addition to serology and culture, leptospires can be detected in tissues using PCR or immunohistochemical staining, especially by direct immunofluorescence.

:: Reference: WHO (pages 11-16; 69)

Credits: O. Chávez

Collection and transportation of samples:
• Serology (MAT, ELISA)

  MAT

• Sample: Minimum of two clotted blood or serum specimens
• Container: Regular sterile tube
• When to collect sample:
• First sample: About 10-12 days after the onset of clinical symptoms
• Second sample: About 10 days after the first sample
• Storage and transportation of samples:
• In order to separate serum from blood, drawn blood must be stored at room temperature for at least 30 minutes for complete clot formation
• Serum must be separated from the clotted blood by centrifugation within 60 minutes of sample collection to prevent hemolysis
• After centrifugation is complete, serum (supernatant) must be decanted using sterile technique into plastic freezing vials
• Serum should be stored at 4 °C for short term and at -20 °C for long time periods
• Serum must be transported at 0 °C to 4 °C

:: Reference: WHO (pages 2-3; 9-14; 63-66); CDC (Appendix 1)

ELISA:

• Sample: Clotted blood or serum specimen
• Container: Regular sterile tube
• When to collect sample: Between 6-8 days after the onset of the first clinical symptoms
• Storage and transportation of samples:
• In order to separate serum from blood, drawn blood must be stored at room temperature for at least 30 minutes for complete clot formation
• Serum must be separated from the clotted blood by centrifugation within 60 minutes of sample collection to prevent hemolysis
• After centrifugation is complete, serum (supernatant) must be decanted using sterile technique into plastic freezing vials
• Serum should be stored at 4 °C for short term and at -20 °C for long time periods
• Serum must be transported at 0 °C to 4 °C

:: Reference: WHO (pages 2-3; 9-14; 66-69); CDC (Appendix 1)

• Culture
  
• Sample: Blood
• Container: Sterile tube with heparin - blood should be collected using aseptic technique
• When to collect sample: Within the first 10 days after the onset of disease (leptospires disappear from the blood after that), and before the administration of antibiotics
• Storage and transportation of samples : Samples for culture should be stored and transported at ambient temperatures, since low temperatures are detrimental to pathogenic leptospires
• Ideally, blood is inoculated at the bedside into blood culture bottles containing culture medium for Leptospira

:: Reference: WHO (pages 9; 81)

• Sample: Urine
• Container: Sterile container
• When to collect sample: 7 days after the onset of clinical symptoms
• Storage and transportation of samples: Samples should be inoculated into an appropriate culture medium not more than 2 hours after voiding (leptospires die quickly in urine)

:: Reference: WHO (pages 9; 81)

• Sample: Postmortem tissues (e.g. brain, cerebrospinal fluid, aqueous humour, lungs, kidney, liver, pancreas and heart, as well as heart blood, if possible)
• Container: Sterile container or tube containing culture medium
• When to collect sample: Postmortem samples should be collected aseptically and as soon as possible after death; they should also be inoculated into culture medium as soon as possible
• Storage and transportation of samples: Postmortem samples should be stored and transported at +4 °C to prevent the autolysis of cells

:: Reference: WHO (pages 9-10; 81)

•  

  Credits: G. Moreno

  Treatment:
  
  
• Initiate antibiotic therapy as soon as possible (preferably before the fifth day after the onset of illness) for suspected cases
• Less severe cases can be treated with oral antibiotics such as amoxycillin, ampicillin, doxycycline or erythromycin; third-generation cephalosporins (ceftriaxone and cefotaxime) and quinolone antibiotics also appear to be effective
• Severe cases (icterohaemorrhagic and/or pulmonary) of leptospirosis should be treated with high doses of intravenous penicillin (1.5 million U/IV every 6 hours), or ceftriaxone (1g/IV per day), or ampicillin (1g/IV every 6 hours), for 7 days. Hospitalization and supportive care with strict attention to fluid and electrolyte balance is also necessary. Peritoneal or haemodialysis is indicated in renal failure
• Jarisch-Herxheimer reactions may occur after penicillin treatment
• Clinicians should never wait for the results of laboratory tests before starting treatment with antibiotics because serological tests do not become positive until about a week after the onset of illness, and cultures may not become positive for several weeks
• Prophylaxis: During high-risk situations, a doctor may prescribe doxycycline 200mg/by mouth once a week as prophylaxis to specific groups, while the risk of infection remains
  

:: Reference: WHO (pages 6-7); OPS (page 112; in Spanish); APHA (pages 306-309)