Page last reviewed: 13/07/2011

Leptospirosis is a type of bacterial infection that is spread by animals. It is caused by a strain of bacteria called leptospira.

Types of leptospirosis

There are two main types of leptospirosis infection:

  • Mild leptospirosis is where a person develops flu-like symptoms, such as headache, chills and muscle pain.
  • Severe leptospirosis is where a person goes on to develop severe, sometimes life-threatening symptoms, including organ failure and internal bleeding. This is caused by the bacteria infecting major organs, such as the liver and kidneys.

Mild leptospirosis is the most common type of leptospirosis, accounting for 90% of cases. It is unclear why a few people go on to develop serious symptoms.

Risk factors for developing severe leptospirosis include:

  • being under five years old
  • being over 65 years old
  • already having a serious health condition, such as pneumonia

How common is leptospirosis?

Leptospirosis is most common in tropical areas of the world. However, it is becoming increasingly widespread in urban areas that have low levels of sanitation, such as in poor areas of large cities in the developing world.

Most cases of leptospirosis are sporadic (infrequent), although large outbreaks have been reported after flooding. 

Globally, it is estimated that 10 million people will get leptospirosis every year. It is difficult to estimate exactly how many people die from leptospirosis because many cases occur in parts of the developing world where causes of death are not routinely reported.

In the coming years, it is anticipated that the number of cases of leptospirosis will continue to increase as a result of global warming and the expected increase in flooding. Some experts have estimated that the fatality rate from leptospirosis could be anywhere between 5 and 25%. Deaths from leptospirosis tend to be higher in countries where access to good quality healthcare is limited.

Cases in Ireland

Rarely, leptospirosis occurs in temperate climates. For example, in 2011, there were 17 reported cases of leptospirosis in Ireland.

Most cases either involved:

  • people who regularly worked with animals and/or water, such as farmers and sewer workers
  • people who took part in water-based activities, such as swimming (including triathlons), canoeing or sailing 

See Leptospirosis - causes for more information.


Mild leptospirosis responds very well to treatment with antibiotics and most people will make a full recovery within a week.

Most people with severe leptospirosis will require admission to hospital so the functions of their body can be supported while the underlying infection is treated with injections of antibiotics.

Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Jaundice is a condition that causes yellowing of the skin and the whites of the eyes, brought on by liver problems.
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.

How it is spread 

Leptospirosis is a zoonotic condition, which means it is spread to humans by animals.

You can catch leptospirosis by touching soil or water contaminated with the urine of wild animals infected with the leptospira bacteria.

Animals known to be carriers of the leptospira bacteria include:

  • cows
  • pigs
  • dogs
  • rodents, particularly rats

Once a young animal is infected, they shed the bacteria in their urine for the rest of their life. Most animals have no symptoms, but up to 1 in 10 infected dogs die from the disease.

Human to human transmission through sex is possible, but very rare.

Page last reviewed: 13/07/2011

The symptoms of leptospirosis usually develop abruptly 7 to 14 days after exposure to the leptospira bacteria.

However, it is possible for symptoms to develop from 3 days to 30 days after exposure.

Mild leptospirosis

Symptoms of mild leptospirosis include:

  • high temperature (fever) that is usually between 38 and 40°C (100.4-104°F)
  • chills
  • sudden headaches
  • nausea (feeling sick)
  • vomiting
  • loss of appetite
  • diarrhoea 
  • cough 
  • sore throat 
  • a non-itchy skin pain
  • muscle pain, particularly affecting the muscles in the calves and lower back
  • conjunctivitis (irritation and redness of the eyes)

The symptoms of mild leptospirosis usually resolve within five to seven days. However, a small number of people will go on to experience a further phase of more serious symptoms, known as severe leptospirosis.

Severe leptospirosis

The symptoms of severe leptospirosis develop one to three days after the symptoms of mild leptospirosis have passed.

The pattern of symptoms usually falls into one of three groups, depending on which organs have become infected:

  • the liver, kidneys and heart (this pattern of infection is known as Weil's disease)
  • the brain
  • the lungs

In rare cases, it is possible to experience all three groups of symptoms at the same time.

Liver, kidney and heart

If these organs become infected, you will probably experience the following symptoms:

  • jaundice (yellowing of the skin and the whites of the eyes)
  • loss of appetite
  • tiredness
  • shortness of breath
  • swollen ankles, feet or hands
  • weight loss
  • muscle aches
  • nausea (feeling sick)
  • nosebleeds
  • a noticeable, painful swelling in your liver
  • a decrease in the amount of urine that you pass
  • chest pain
  • rapid and irregular heartbeat

Left untreated, your kidneys may lose their ability to function. This is known as kidney failure and it can be fatal.

The brain

There are two ways that the brain can become infected:

Both types of brain infection cause similar symptoms, including:

  • high temperature (fever) of 38°C (100.4°F) or above
  • nausea (feeling sick)
  • vomiting
  • changes in mental state, such as confusion,
    drowsiness or disorientation
  • seizures (fits)
  • aversion to bright lights (photophobia)
  • inability to speak
  • inability to control physical movements
  • stiff neck
  • a blotchy red rash that does not fade or change colour when you place a glass against it
  • uncharacteristic behaviour, such as being unusually aggressive

Left untreated, the infection can cause brain damage, coma and death.

The lungs

A leptospirosis infection that spreads to the lungs presents the most serious health threat because it carries a significant risk of death. This is because the bacteria damage the lung tissues, which can result in massive internal bleeding and loss of lung function, both of which can be fatal.

Symptoms include:

  • a high temperature, which can be as high as 40.5°C (105°F)
  • shortness of breath
  • coughing up blood (sometimes the amount of blood coughed up is so great that a person can choke on it)
BacteriaBacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.DiarrhoeaDiarrhoea is the passing of frequent watery stools when you go to the toilet.HeartThe heart is a muscular organ that pumps blood around the body.JaundiceJaundice is a condition that causes yellowing of the skin and the whites of the eyes, brought on by liver problems.KidneysKidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.LiverThe liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.Loss of appetiteLoss of appetite is when you do not feel hungry or want to eat.VomitingVomiting is when you bring up the contents of your stomach through your mouth.

Page last reviewed: 13/07/2011

Leptospirosis is caused by a strain of bacteria called leptospira, which are found in certain animals including:

  • mice
  • rats
  • pigs
  • cattle
  • horses
  • dogs
  • sheep
  • bats
  • raccoons

The bacteria live inside the animal's kidneys and can be passed out in their urine. Bacteria passed into soil or water can survive for several weeks or even months.

You can become infected by the leptospira bacteria by drinking contaminated water, or if contaminated water or soil comes into contact with your eyes, mouth, nose or any unhealed cuts in the skin. Less commonly, the infection can be passed on to humans who come into close physical contact with the blood of an infected animal.

Human cases of leptospirosis are rare, but occasional outbreaks can occur, particularly at events that involve close contact with infected water sources, such as competitive freshwater swimming. It is also possible for a person to become infected after a natural disaster, such as a flood.

Human to human transmission of infection is rare, but thought to occur during sex or by an infected mother passing on the infection to her baby while breastfeeding.

Geographical risk factors

Leptospirosis is found throughout the world, including Western Europe, but it is most common in tropical and subtropical areas. This is because the leptospira bacteria are able to survive longest in hot and humid conditions. The countries and regions where leptospirosis is most common include:

  • India
  • China
  • Southern Russia
  • South East Asia
  • Africa
  • parts of Australia
  • Central America
  • parts of South America (particularly Brazil)
  • the Caribbean

Popular tourist destinations that have a higher-than-average rate of leptospirosis include:

  • Hawaii
  • Thailand
  • Jamaica
  • Barbados
  • Australia
  • New Zealand

If you are travelling to these parts of the world, there are certain outdoor activities that could bring you into contact with contaminated water or soil and may place you at a slightly higher risk of contracting leptospirosis. For example:

  • swimming, particularly if you submerge your head under the water for long periods of time
  • sailing
  • rafting
  • camping in rural areas
  • caving or potholing
  • canoeing
  • trail biking
  • walking barefoot

Areas of the developing world where there has been sudden flooding tend to have an associated outbreak of leptospirosis. This is because previously clean sources of drinking water can become contaminated by flood water. Wading through contaminated floodwaters and cleaning up after flooding are also risk factors.

Occupational risk factors

There are several occupations that increase your risk of contracting leptospirosis. However, this risk is only significant if you are working in the following occupations:

  • farmers, particularly pig, cattle
  • sewage workers
  • people who regularly work with animals, such as vets
  • freshwater fishermen
  • people who work with dead animals, such as butchers or abattoir workers (an abattoir is where animals are killed for their meat)

See Leptospirosis - prevention for information and advice about how to reduce your risk of contracting leptospirosis.

Page last reviewed: 13/07/2011

Mild leptospirosis can be difficult to diagnose when it is in its acute (early) stage because it shares symptoms with many other more common infections, such as influenza (flu).

Also, many of the tests that are usually used for investigating flu-like symptoms are not very effective at diagnosing leptospirosis.

Therefore, a diagnosis of leptospirosis is usually only considered if you are experiencing the symptoms of severe leptospirosis.

To diagnose leptospirosis successfully, a detailed personal history is usually required. You should tell your GP if you:

  • have recently travelled to parts of the world where leptospirosis is widespread
  • have recently been exposed to a freshwater source, such as a river, lake, drain, canal or pond
  • have an occupation that involves exposure to animal urine or animal blood, such as farming, caring for animals (veterinary care) or working in an abattoir

A diagnosis of leptospirosis can be confirmed by running a series of blood and urine tests to detect the presence of the leptospira bacteria in your blood or urine.

Page last reviewed: 13/07/2011

Acute leptospirosis

Most cases of acute leptospirosis can be successfully treated with a five-to-seven-day course of antibiotic tablets. A tetracycline antibiotic called doxycycline is the preferred choice.

Side effects of doxycycline include:

These side effects should pass once you complete the course of antibiotics. An alternative antibiotic, such as erythromycin, can be used instead of doxycycline.

Side effects of erythromycin include:

  • nausea (feeling sick)
  • stomach pain
  • vomiting
  • diarrhoea

It is very important that you finish the prescribed course of antibiotics, even if you are feeling better. This is because stopping treatment before all of the bacteria have been killed may trigger the return of a more serious infection.

Painkillers that are available over the counter, such as paracetamol or ibuprofen, can be used to help relieve symptoms, such as headache, high temperature and muscle pain.

Contact your GP for advice if, despite treatment, your symptoms fail to improve after seven days.

Severe leptospirosis

Almost all cases of severe leptospirosis will require admission to hospital. The underlying infection will be treated with intravenous antibiotics (antibiotics that are injected directly into the bloodstream).

If you have experienced organ damage, additional equipment may be required to support the functions of your body. For example:

  • a ventilator to assist your breathing
  • dialysis, which is where the functions of your kidneys are artificially replicated by removing waste materials from your blood
  • intravenous fluids to restore the fluids and nutrients in your body

The amount of time that you will need to spend in hospital will depend on how well you respond to the antibiotics and the extent of any organ damage. Some people may be well enough to leave hospital within a few weeks, while others may require several months of hospital care.

Leptospirosis and pregnancy

The course of a leptospirosis infection during pregnancy and its resulting effect on the baby can be highly unpredictable.

In some cases, the infection can spread to the unborn child, resulting in the death of the child and a miscarriage or stillbirth. In other cases, the baby is totally unaffected by the infection and the pregnancy proceeds as normal.

If you develop the symptoms of leptospirosis during pregnancy (even mild symptoms), you may be admitted to hospital so your health and the health of your baby can be carefully monitored.

Page last reviewed: 13/07/2011

Water sports in Ireland

In Ireland the rates of leptospirosis are very low, so there is no reason why you should not participate in freshwater recreational activities, such as canoeing, swimming - especially triathlons, sailing, water skiing or windsurfing.

An expert in leptospirosis has estimated that the risk of contracting a leptospirosis infection by taking part in these types of activities is as low as 1 in 10 million.

However, if you are regularly involved in freshwater activities, it is a sensible precaution to cover any cuts and grazes that you have with a waterproof dressing because there are other waterborne infections that you can catch, such as hepatitis A (a viral infection) or giardiasis (an infection caused by parasites). You should also shower or bathe after freshwater activities.

At work

If you have an occupation where you come into contact with animals (particularly rodents) and/or sources of contaminated water, such as farming or working with sewers or drains, wear adequate protective clothing. This could include waterproof gloves and boots, goggles and a mask.

Travelling abroad

If you are travelling to parts of the world where leptospirosis is widespread, you may wish to limit your exposure to fresh water. If you are unable to avoid coming into contact with freshwater sources, such as rivers, ponds or lakes, you should ensure that you wear adequate protective clothing.

You should also only drink sealed bottled water or fresh water that has been boiled. Always cover any cuts or grazes with waterproof dressings and clean any wounds as soon as possible.

Try to minimise your exposure to animal urine by avoiding areas where animals may have urinated, such as bedding and litter trays. If you suspect that you have been exposed to animal urine, clean the affected area of skin as soon as possible.

Never touch a dead animal with your bare hands.

Antibiotic prophylaxis

Antibiotic prophylaxis is where you take antibiotics as a precaution against becoming infected. However, there is limited evidence regarding the effectiveness of antibiotic prophylaxis for leptospirosis, so it is usually only used in exceptional circumstances, such as:

  • for emergency workers working in disaster zones where there is known to be an outbreak of leptospirosis cases
  • for soldiers serving in areas where rates of leptospirosis are high
  • for animal workers who may have been contaminated by an animal that is known to be a carrier of the leptospira bacteria

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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