Leptospirosis is caused by infection with Leptospira bacteria. The infection passes from animals (commonly rats, cattle, pigs and dogs) to humans. In most cases, leptospirosis causes a mild illness. But, in some people, a more severe illness occurs. This more severe form is commonly referred to as Weil's disease. The main treatment for leptospirosis is antibiotics and most people make a full recovery.
Leptospirosis is caused by infection with the bacteria Leptospira. It is a type of zoonosis infection (an infection that can be passed from animals to humans).
Both wild and domestic animals can become infected with Leptospira, including rats, cattle, pigs and dogs. The bacteria can live for many years within the animal's kidneys and can be passed out in their urine into water, soil, vegetation and mud, where they can survive for several months. Often, infected animals show no outward signs of illness.
Leptospirosis can be passed on to humans through direct contact with the bodily fluids or tissues of an infected animal (such as urine) or through contact with soil or water contaminated with infected urine. The bacteria usually get into the human body through a cut or small abrasion in the skin. They can also pass through mucous membranes such as the skin that lines the mouth, the nose and the front of the eye. The bacteria may also be inhaled and enter the body via the lungs. Once inside the body, Leptospira have the ability to pass via the bloodstream and the lymph system to the internal organs.
In the majority of cases, leptospirosis causes a mild illness but, in some people, a more severe form of leptospirosis occurs. This more severe form is commonly referred to as Weil's disease, so called after Dr Weil who first described it.
Animals in countries all over the world carry Leptospira bacteria but the infection is more common in tropical areas with warmer climates. In the UK, leptospirosis is not very common. The Health Protection Agency reports that there are around 50 to 60 cases in England and Wales each year. That is about one case per million people per year.
The risk of developing leptospirosis is greater in certain groups of people - for example, those whose work involves exposure to animals, such as farmers, vets, abattoir workers and rodent control workers. Sewage workers also have an increased risk of infection as do people who take part in water sports such as rafting, diving, fishing, canoeing, potholing or hiking through water. Leptospirosis has also been reported after episodes of flooding.
As mentioned above, there are two forms of leptospirosis: a mild form causing a flu-like illness and a more severe form (Weil's disease) which can cause jaundice and liver and kidney failure. Around 9 out of 10 people just develop the mild form of the illness. The remaining 1 in 10 people develop Weil's disease. It is not clear why Weil's disease only develops in some people.
Symptoms of leptospirosis are first noticed some time between 2 and 30 days after exposure to the bacteria but they most usually develop after around 7 to 14 days. Some people with mild leptospirosis may develop no symptoms at all.
In both the mild and the severe forms of leptospirosis, flu-like symptoms develop first. They tend to last for between 5 and 7 days and can include:
During this stage of the illness, the bacteria are spreading throughout the body via the bloodstream. The majority of people then recover as their immune system clears the infection. However, in some people, about a week after the flu-like symptoms have passed, a second stage of the illness then develops (Weil's disease). Symptoms of this second stage can include:
During this second stage, bacteria begin to infect the organs of the body, such as the kidneys, the liver, the brain, the eyes, the heart and the lungs. Different organs may be infected in different people but commonly the kidneys and the liver are affected and kidney or liver failure can occur. The lungs may also become involved causing symptoms such as cough, shortness of breath and bleeding within the lungs (which can lead to coughing up of blood). Some people develop symptoms similar to meningitis. The heart may be affected in others, leading to myocarditis (inflammation of the heart muscle) and sometimes heart failure.
In the early stages of leptospirosis, it may be quite difficult to tell the symptoms apart from the flu. If you know that you have been in contact with water that was possibly contaminated with animal urine, or if you work with animals, you should tell your doctor and this can help to alert them to the possibility of leptospirosis.
Tests are usually carried out to confirm the diagnosis. You may be asked to provide a urine sample to look for Leptospira in your urine. Blood testing can also confirm the diagnosis by looking for evidence of the bacteria in your bloodstream.
Other tests may also be done to assess the severity of your illness. For example, blood tests to look for anaemia, to look at the clotting of your blood and to look at how your kidneys and liver are functioning. A chest X-ray may be done to look for lung problems.
Antibiotics are the main treatment, with penicillin or doxycycline the main antibiotics that are used. Antibiotics are usually prescribed as soon as possible after leptospirosis is diagnosed. In mild leptospirosis, antibiotic tablets may be all that is needed. In more severe cases, intravenous antibiotics (antibiotics given into your veins) are used.
People with mild leptospirosis may be treated at home. Those with the severe form of infection are usually admitted to hospital for treatment and monitoring.
Other supportive treatment may be needed. For example, painkillers to help with muscle and joint pains and medication to help bring down high fever, such as paracetamol. If you are not able to drink plenty of fluids, to avoid dehydration you may need to be given fluids intravenously. In severe cases, close monitoring of the heart, help with breathing, or kidney dialysis may be needed.
As discussed above, 9 out of 10 people have a mild form of leptospirosis and the prognosis (outlook) in such cases is very good. Most people recover fully within two to six weeks but some may take up to three months to get better.
In more severe cases (Weil's disease), the outlook depends on which organs of the body are involved and to what extent. A few people each year in England and Wales die from leptospirosis. Death is usually due to internal bleeding, kidney or lung complications.
The best way to prevent leptospirosis is to avoid contact with potentially infected animals and potentially contaminated soil and water. You should avoid swimming or entering water that might be contaminated with animal urine.
Those working with animals that could be infected should wear protective clothing and equipment including gloves, eye protection and footwear. They should also pay strict attention to hygiene, including meticulous handwashing after exposure to animals. Rodent control can also help to prevent infection - for example, rubbish disposal and ensuring that rodents cannot get into buildings.
If there is contact with fresh, surface waters, for example, canals, ponds or rivers, or with rats, the HPA advises you to:
For those at very high risk of leptospirosis for a short period of time, the antibiotic doxycycline may be prescribed to reduce the chance of developing infection. Vaccination of some animals is carried out to help to control the infection. No human vaccine against leptospirosis is currently available in the UK.