What is Leptospirosis.

Leptospirosis is a bacterial disease that affects both humans and animals. Humans become infected through direct contact with the urine of infected animals or with a urine-contaminated environment. The bacteria enter the body through cuts or abrasions on the skin, or through the mucous membranes of the mouth, nose and eyes. Person-to-person transmission is rare.

In the early stages of the disease, symptoms include high fever, severe headache, muscle pain, chills, redness of the eyes, abdominal pain, jaundice, haemorrhages in the skin and mucous membranes, vomiting, diarrhoea, and rash.


  • Leptospirosis is acquired through direct or indirect contact with the urine of an infected animal. The spirochete most commonly enters through abrasions in the skin or through the conjunctiva
  • The principal source of infection in humans is the rat, although other sources include dogs, livestock, rodents, and other wild animals
  • The incubation period is usually 7 to 13 days but can range from 2 to 26 days
  • Two syndromes occur: anicteric leptospirosis, which is typically self-limiting and consists of a septicemic phase and an immune phase, and icteric leptospirosis (Weil disease), which is characterized by severe jaundice, liver failure, and renal failure and may be fatal, with mortality rates ranging from 5% to 40%
  • Disease onset is abrupt, and the anicteric illness is typically biphasic, with an acute leptospiremic phase followed by an immune-mediated leptospiruric phase
  • Neonatal infections can occur


Incidence and prevalence:

  • The incidence of leptospirosis in the U.S. overall is 0.05 cases per 100,000 persons, with an incidence of 12.8 cases per 100,000 persons in Hawaii
  • The frequency of infection is variable because there is considerable geographic variation; in some developing countries, 80% of the population shows serologic evidence of infection
  • A higher frequency of infection is seen in persons with occupations known to be associated with increased risk; approximately 15% of veterinary workers and slaughterhouse workers show serologic evidence of infection


  • Infection usually occurs in adolescents or young adults and is more common in men (male-to-female ratio of 4:1), possibly because of greater participation in high-risk occupations or recreational activities; peak incidence is in men aged 30 to 39 years
  • Leptospirosis is seen worldwide, except in the polar regions; human infection is endemic in most temperate and tropical climates, with peak occurrence during the summer months or after periods of high precipitation. In the U.S., most cases are reported in the Southern and Pacific coastal states, but Hawaii consistently reports more cases than any other state
  • Epidemics in developing countries are associated with exposure to flood waters during the rainy season
  • Occupational groups that have been identified as being at increased risk for leptospirosis include slaughterhouse workers, sewage workers, veterinary workers, farmers, and military personnel
  • Leptospirosis is up to 10 times more common among people living in rural areas compared with those living in urban areas, although urban dwellers who live in rat-infested environments or areas disrupted by war are also at risk

Causes and risk factors


  • Infection with spirochetes of the genus Leptospira

Risk factors:

  • Occupational factors: farmers (described in sugarcane, rice, and fish farmers), sewage workers, slaughterhouse workers, veterinary surgeons, field workers, and military personnel are at greatest risk
  • Recreational factors: swimming, windsurfing, and other recreational activities that may result in contact with contaminated water or soil
  • Household exposure: direct contact or exposure to soil contaminated with urine from domesticated livestock, pet dogs, or infected rodents


Not applicable.

Primary prevention

Summary approach

  • Because a vaccine for humans is not available in most countries, prevention revolves around reducing exposure, either by avoiding situations that pose risk or by the use of protective clothing, disinfection practices, rodent control measures, and immunization of livestock
  • Among persons at high risk, immunization programs have proven effective in some areas of Asia and Europe, and doxycycline prophylaxis has been studied

Population at risk

  • Slaughterhouse workers
  • Sewage workers
  • Veterinary workers
  • Farmers
  • Military personnel

Preventive measures

  • Protective clothing (rubber boots, gloves, goggles) should be worn when exposure is unavoidable
  • In applicable settings, surfaces and equipment should be disinfected
  • Rodent control measures are important in settings where they can be effectively applied
  • Immunization of livestock may reduce some occupational exposures, but available veterinary vaccines are not fully protective, and frequent boosters are required
  • Doxycycline prophylaxis has been studied for use in persons at high risk, but data are insufficient to make a recommendation


  • A randomized, controlled trial (RCT) comparing doxycycline versus placebo for the prevention of leptospirosis during a seasonal outbreak in an endemic area found no significant difference between groups in terms of infection rate, but doxycycline significantly reduced the rate of clinical illness in those who were infected.[1]Level of evidence: 1
  • A systematic review identified three RCTs evaluating the use of doxycycline for the prevention of leptospirosis, two of which involved preexposure prophylaxis. Pooled data showed no statistically significant difference in the rates of serologically confirmed infection between participants who received prophylaxis and those who did not.[2]Level of evidence: 1




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