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Leptospirosis is a zoonosis (infection transmitted from animals to humans). It is caused by bacteria of the genus Leptospira (referred to as leptospires). These infect a variety of wild and domestic animals. Infected animals excrete leptospires in their urine but may not exhibit symptoms of active infection. 

Leptospirosis is more common in tropical areas of the world, but is also found in temperate areas, including Europe. It can lead to potentially fatal infections of the kidney, liver, brain, lung or heart.

Humans are considered to be a dead-end or accidental host of leptospires. Infected animals carry the bacteria in their kidneys. They can excrete leptospires in their urine for some time, and spread infection to other animals or humans coming into direct or indirect contact with the infected urine, tissues or secretions or water which has been contaminated with infected animal urine. Leptospires enter the body through cut or damaged skin, but may also pass across damaged or intact mucous membranes, and the eyes. Person-to-person spread is extremely rare, if it occurs at all. 

Thus the two most common ways to develop leptospirosis are:

  • Drinking or contact with water (such as by swimming, rafting or kayaking) or soil that has been contaminated by urine or body fluids of infected animals
  • Exposure to the urine or body fluids of infected animals

Often the infected animal does not become ill. For example, neither rats nor cattle, appear ill. In general, herbivorous animals seem more likely to become, and remain, infected. However nearly all mammals are capable of carrying the bacteria and may therefore spread the disease among others of their own kind, and to other species, including man. Common animal reservoirs include rodents, cattle and pigs.

People most at risk for Leptospirosis infection include farm workers and people who have recreational contact with water.

Incubation Period
Symptoms usually develop 7-21 days after initial infection with leptospires, though rarely the incubation period can be as short as two to three days or as long as 30 days.


Common symptoms of leptospirosis include:

  • Fever
  • Chills
  • Headache
  • Muscle Aches
  • Vomiting
  • Diarrhoea
  • Abdominal Pain
  • Jaundice (yellowing of the skin and eyes)
  • Skin Rash
  • Red Eyes

Infection with leptospires can cause no symptoms at all, a mild flu-like illness, or severe illness the presentation of which is called Weil's disease (Weil's syndrome), with jaundice and kidney failure.

Leptospirosis is an acute biphasic illness. Some cases may be asymptomatic or may present in the first phase with the abrupt onset of a flu-like illness, with a severe headache, chills, muscle aches, and vomiting. This is known as the bacteraemic phase, when the leptospires spread through the blood to many tissues, including the brain. This phase may resolve without treatment.

In some cases, an immune phase may follow with a return of fever, jaundice (yellow skin and eyes), red eyes, abdominal pain, diarrhoea, or a rash.
In more severe cases, there may be failure of some organs, e.g. the kidneys, or meningitis.

Generally, cases will recover fully within two to six weeks but some may take up to three months. After infection, immunity develops against the infecting strain, but this may not fully protect against infection with unrelated strains.

Complete recovery is the usual outcome after leptospirosis and there are unlikely to be any long term effects.

Leptospirosis is treated with antibiotics such as penicillin or doxycycline, which should be given early in the course of the disease. Intravenous antibiotics may be needed for people with more severe symptoms.

There is no human vaccine available that is effective against leptospirosis. For people who may be at high risk for short periods, especially through their occupation, taking doxycycline (200mg weekly) may be effective.

General prevention advice includes taking measures to reduce rodent populations, such as clearing rubbish and preventing rodent access into buildings. Animal vaccines are available, and immunising and treating infected animals is worthwhile. The risk of acquiring leptospirosis can be greatly reduced by not swimming or wading in water that might be contaminated with animal urine.

The following simple precautions below can reduce risk infection, especially in people who might come into contact with contaminated water or with rats.

  • Cover cuts, scratches or sores with a waterproof plaster and thoroughly clean cuts or abrasions received during activities
  • Wear appropriate protective clothing, gloves or protective footwear
  • Wash or shower promptly after water sports, especially if you fall in
  • Avoid capsize drill or rolling in stagnant or slow moving water
  • Wear thick gloves when handling rats
  • Wash hands after handling any animal, and before eating