Leptospirosis is caused by a strain of bacteria called leptospira, which is found in certain animals and can spread to humans.

These animals include:

• rats and mice
• most farm animals, such as pigs, cattle, horses and sheep
• dogs

It is rare to catch leptospirosis from domestic pets, although there have been cases where the infection was caught from pet rats.

An animal carrying the leptospira bacteria may show no outward signs of illness. 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.

It is possible to become infected with the leptospira bacteria if contaminated water or soil comes into contact with your eyes, mouth, nose or any open cuts in the skin. The bacteria can also be spread through rodent bites or by drinking contaminated water. Less commonly, the infection can be passed to humans who come into close physical contact with the blood or tissues of an infected animal.

Outbreaks of leptospirosis can also occur, particularly at events that involve close contact with infected fresh water sources, such as some water sports. It is also possible for people to become infected after a natural disaster, such as a flood.

Human to human transmission of infection is extremely rare, but it is thought that it may be possible during sex or by an infected mother passing it on to her baby while breastfeeding.

Where is leptospirosis found?

Leptospirosis is found throughout the world, including western Europe, but 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
• South East Asia
• Africa
• Australia
• Central and South America  
• the Caribbean

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

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

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.

Occupational risk

There are several occupations that increase your risk of contracting leptospirosis. However, this risk is most significant if you are working in the parts of the world listed above, rather than in the UK. These occupations include:

• farmers, particularly pig, cattle and rice farmers
• 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

Read about preventing leptospirosis for information and advice about how to reduce your risk of contracting the disease.

Leptospirosis can be difficult to diagnose in its mild early stages, as it shares symptoms with other more common infections.

Many cases may initially be mistaken for conditions such as influenza (flu). Leptospirosis is therefore usually only diagnosed if symptoms are severe.

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.

Scans such as a chest X-ray may also be carried out if it is felt your organs have been affected.

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

In 90% of cases, leptospirosis only causes mild flu-like symptoms, such as headache, chills and muscle pain.

However, in some cases the infection is more severe and can cause life-threatening problems, including organ failure and internal bleeding. In its most severe form, leptospirosis is also known as Weil’s disease.

The common mild symptoms mean that most leptospirosis infections are hard to diagnose. Diagnosis is easier if the infection causes more serious problems.

A detailed history of places you have been and any animals you have been in contact with can help with a diagnosis.

Read more about the symptoms of leptospirosis and diagnosing leptospirosis.

Why does leptospirosis happen?

Leptospirosis 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 cattle, pigs, dogs and rodents, particularly rats.

Although the condition is uncommon in the UK, people who regularly deal with animals, such as farmers and vets, have a higher risk of developing leptospirosis.

You may also be at a higher risk if you frequently come into contact with sources of freshwater, such as rivers and lakes. This might be because of your occupation or through taking part in recreational activities such as water sports and fishing.

Transmission between humans is incredibly rare.

Read more about the causes of leptospirosis.

Cases in the UK

Leptospirosis is rare in the UK. For example, only 44 cases were reported in England and Wales during 2011. Of these, 15 cases originated overseas and none were fatal.

Most of the people affected either worked with livestock or contracted the condition from sewage or freshwater sources.

Can leptospirosis be prevented?

The risk of contracting leptospirosis in the UK is so low that you don’t need to take drastic measures to avoid the condition.

If you work with animals – dead or alive – or are in regular contact with freshwater sources, you can help protect yourself from leptospirosis by wearing appropriate protective clothing and by cleaning and dressing wounds.

This advice is particularly useful if you are travelling to an area where leptospirosis is more common.

Read more about preventing leptospirosis.

How is leptospirosis treated?

Leptospirosis is treated with a course of antibiotics.

For mild forms of leptospirosis, antibiotic tablets that can be taken at home are usually used for about a week.

Most people with more 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.

Read more about treating leptospirosis.

Although leptospirosis is rare in the UK, some simple steps can help reduce your chances of developing the condition.

Water sports in the UK 

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

However, if you are regularly involved in freshwater activities, it is a sensible precaution to cover any cuts and grazes 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) 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 freshwater sources, such as rivers, ponds or lakes. If you are unable to avoid these, you should ensure 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 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.

Read about the causes of leptospirosis for information on areas of the world where leptospirosis is more common.

Antibiotics

Antibiotics can sometimes be taken as a precaution against becoming infected. However, there is limited evidence this works for leptospirosis, so the treatment 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 contaminated by an animal known to be a carrier of the leptospira bacteria

Animal vaccination

At the moment, there isn’t a vaccine that protects humans from leptospirosis, but it is possible to vaccinate cattle, dogs and some other animals.

If you think you may be at risk of contracting leptospirosis from one of your animals, you may want to consider getting them vaccinated.

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

However, it is possible for symptoms to develop from between two and 30 days after exposure.

About 90% of leptospirosis infections only cause mild symptoms, including:

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

These symptoms usually resolve within five to seven days. However, in about 10% of cases people go on to experience more serious symptoms.

Severe leptospirosis

Severe leptospirosis infections are sometimes called Weil’s disease. The symptoms of a severe infection usually develop one to three days after the more mild symptoms 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
• 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 are affected, 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
• a noticeable, painful swelling in your liver
• a decrease in the amount of urine that you pass
• chest pain
• rapid and irregular heartbeat

If left untreated, your liver or kidneys may lose their ability to function. Loss of kidney function is known as kidney failure and can be fatal.

The brain

There are two ways that the brain can be affected:

• the outer layer of the brain becomes infected (meningitis)
• the brain tissue becomes infected (encephalitis)

Both types of brain infection cause similar symptoms, including:

• a high temperature (fever) of 38°C (100.4°F) or above
• nausea and vomiting
• changes in mental state, such as confusion,
  drowsiness or disorientation
• uncharacteristic behaviour, such as being unusually aggressive
• seizures (fits)
• aversion to bright lights (photophobia)
• inability to speak
• inability to control physical movements
• stiff neck

If left untreated, the infection may cause brain damage and can be fatal.

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.

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)

Leptospirosis is usually treated with a course of antibiotics, although their effectiveness has not been conclusively proven.

Most cases of leptospirosis are mild and can be successfully treated with a five to seven-day course of antibiotic tablets. Penicillin or a tetracycline antibiotic called doxycycline are the preferred choices.

Common side effects of antibiotics include:

• indigestion 
• diarrhoea
• nausea
• vomiting

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

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.

More information about the medicines that are used to treat leptospirosis can be found on the leptospirosis medicines guide page.

Severe leptospirosis

If you develop a more severe leptospirosis infection, you will need to be admitted 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.