Leptospirosis is a relatively rare bacterial infection that affects people and animals. It can pass from animals to humans when an unhealed break in the skin is exposed to water or soil that has been contaminated with animal urine. It is not usually transmitted between people.
Leptospirosis is caused by a strain of the Leptospira bacterium, and it can progress to potentially fatal conditions such as Weil's disease or meningitis.
The bacteria can enter the body through broken skin, the eyes, or mucous membranes. Animals that transmit the infection to humans include rats, skunks, opossums, foxes, and raccoons.
Leptospirosis is more common in tropical areas, where it affects 10 or more people in every 100,000. In temperate climates, the incidence is estimated between 0.1 and 1 per 100,000. In an epidemic, it can affect 100 or more in every 100,000.
People traveling to tropical areas have a greater risk of exposure.
Contents of this article:
Types of leptospirosis
Leptospirosis is an infectious disease that can have serious complications.
There are two main types of leptospirosis:
Between 5 percent and 15 percent of cases can progress to severe leptospirosis. Organ failure, internal hemorrhaging, and death can result if the bacterium infects the liver, kidneys, and other major organs. The Centers for Disease Control and Prevention (CDC) puts the fatality rate between 1 percent and 5 percent.
Leptospirosis is less likely to be fatal in countries with more effective health care systems.
Those more likely to develop severe leptospirosis tend to be those who are already sick, for example, with pneumonia, those under the age of 5 years, and those in older age.
Who is at risk?
Leptospirosis is more common in the tropics, but it may also occur in the poor parts of large cities in developing nations that are not in tropical areas. The bacterium thrives in hot and humid environments. It tends to be sporadic.
Higher incidences of leptospirosis are found in parts of Africa, India, China, Central America, Brazil, Caribbean, South East Asia, and Southern Russia.
In some countries, wide sections of the population are at risk, for example, when working in rice fields or sugarcane plantations, using river or lake water for washing and cooking, or following a natural disaster.
Tourist hotspots where leptospirosis sometimes occurs include New Zealand, Australia, Hawaii, and Barbados.
Flooding increases the risk of an outbreak. If climate change leads to more cases of flooding around the world, leptospirosis may become more common.
Leptospirosis in developed nations
In 1995, leptospirosis ceased being a notifiable disease in the United States, but it was reinstated in January 2013. The biggest outbreak was in 1998, when 110 people became infected. Between 100 and 200 people are identified in the U.S. each year, according to the CDC. Around half of the cases in the U.S. occur in Hawaii.
In developed countries, those most at risk are:
- Sewage workers
- Farm and agricultural workers who have regular contact with animals or infected water or soil
- Pet shop employees and veterinarians
- Abattoir workers and meat handlers
- Those involved in recreational water sports, such as sailing or canoeing
- Military personnel
Death rates in developed nations are much lower than in poorer countries, due to effective health care.
Signs and symptoms
The signs and symptoms of leptospirosis usually appear suddenly, about 5 to 14 days after infection, but the incubation period can range from 2 days to 30 days.
Signs and symptoms of mild leptospirosis include:
Fever and chills are signs of leptospirosis.
- Headaches that may start suddenly
- High fever
- Muscle pain, particularly lower back and calves
- Poor appetite
- Red and irritated eyes
- Skin pain
The patient usually recovers within a week without treatment, but a small proportion will go on to develop severe leptospirosis.
Signs and symptoms of severe leptospirosis will appear a few days after mild leptospirosis symptoms have disappeared.
They depend on which vital organs have been affected.
If the heart, liver, and kidneys are affected, the person will experience:
- Irregular, often fast, heartbeat
- Muscle pains
- Pain in the chest
- Poor appetite
- Swelling in the hands, feet or ankles
- Unexplained weight loss
- Jaundice, seen in a yellowing of the whites of the eyes, tongue, and skin
Without treatment, this can lead to life-threatening kidney failure.
If the brain is affected, meningitis, encephalitis, or both may develop.
Meningitis is an infection on the outer layer of the brain, while encephalitis refers to infection of brain tissue. Both conditions have similar signs and symptoms.
These may include:
- A blotchy skin rash, which does not change color or fade when a glass is pressed against it
- Confusion or disorientation
- Fits or seizures
- High fever
- Photophobia, or sensitivity to light
- Problems with physical movements
- Stiff neck
- Inability to speak
- Aggressive or unusual behavior
Untreated meningitis or encephalitis can result in serious brain damage, and it may be life-threatening.
If the lungs are affected, the person cannot breathe. This is the most serious and life-threatening of all leptospirosis complications.
Signs and symptoms include:
- High fever
- Coughing up blood
In severe cases, there may be so much blood that the patient chokes.
The Leptospira bacteria can exist in raccoons, bats, sheep, dogs, mice, rats, horses, cattle, buffaloes, and pigs.
Rodents can pass on leptospirosis to humans.
The bacteria inhabit the animals' kidneys and are expelled through urination, infecting the soil or water supplies.
Soil or water can remain contaminated for months.
People can become infected through:
- Drinking contaminated water
- Unhealed cuts or wounds that come into contact with contaminated water or soil
- The eyes, nose, or mouth coming into contact with contaminated water or soil
- Less commonly, contact with the blood of an infected animal
Humans are rarely infected, except in times of flooding. Humans rarely infect other humans, but transmission may occur during sexual intercourse or breastfeeding.
Diagnosis, treatment, and prevention
Early-stage, mild leptospirosis is hard to diagnose, because the symptoms can resemble those of flu and other common infections, and reliable diagnostic tests are lacking.
If a physician suspects severe leptospirosis, the patient may undergo specific diagnostic tests.
The doctor will ask about any recent travel, especially to areas where leptospirosis is common.
They may ask if the person has been swimming in a lake, pond, canal, or river, about any activities that occurred in a slaughterhouse, on a farm, relating to animal care, or anything that might have involved contact with animal urine or blood.
A number of blood and urine tests can confirm or rule out leptospirosis.
Patients with severe leptospirosis will need to be hospitalized and given antibiotics intravenously.
Depending on which organs are affected, the patient may need a ventilator to assist in breathing, or dialysis, if the kidneys are affected.
Intravenous fluids can provide hydration and essential nutrients.
Hospital stays may range from a few weeks to several months, mostly depending on how the patient responds to antibiotic treatment, and how severely their organs are affected or damaged.
During pregnancy, it is possible for leptospirosis to affect the fetus, so a woman who has the infection while pregnant will need to be hospitalized for monitoring.
In non-tropical, developed nations, the risk of leptospirosis is very small, and most people do not need to avoid doing water sports.
Fresh water leisure activities can increase the risk in tropical climes.
However, those who regularly swim in freshwater should make sure that any skin cuts are covered with a waterproof dressing, to protect against a range of infections, including hepatitis A and giardiasis. After swimming in fresh water, it is a good idea to shower thoroughly.
Those who work with animals or potentially contaminated water or soil should wear protective clothing and comply with local or national rules and regulations. They may need to wear gloves, masks, boots, and goggles.
People who travel to areas where leptospirosis is common, should:
- Avoid swimming in fresh water
- Only drink water that is boiled or from a sealed bottle
- Clean and cover any skin wounds with a waterproof dressing
Emergency workers or military personnel in disaster zones might have to take antibiotics as a precautionary measure.