Guidance

Leptospirosis

The characteristics, diagnosis and epidemiology of infections caused by spirochaetes of the genus Leptospira (Leptospires).

Characteristics

Leptospirosis is a zoonotic infection caused by spiral-shaped bacteria of the genus Leptospira (also referred to as leptospires)

Leptospires may be either:

  • pathogenic, capable of causing disease in animals or humans
  • saprophytic, free-living in surface waters and not known to cause diseas

There are at least 23 named species of Leptospira. The majority of infections are caused by L interrogans and related strains, but other species may occasionally cause infection in humans.

Wild and domestic animals may also be infected by leptospirosis, or they may carry the organism asymptomatically. Animals can spread the leptospires in their urine. Nearly all mammals are capable of carrying the bacteria and may spread the disease among their own kind and to other species, including humans. Common animal reservoirs include rodents, cattle and pigs.

Transmission

Cases of leptospirosis are reported worldwide, although the disease is more prevalent in tropical regions as the bacteria can survive longer in warm, humid environments. This global distribution is in part due to the large number of animal hosts able to maintain and transmit the infection: over 160 different animal species have been identified as natural carriers of Leptospira bacteria. The bacteria live in the kidneys of host animals, which are often asymptomatic.

Humans can become infected through direct exposure to animal urine, or exposure to urine contaminated environments, such as canals, rivers and lakes. The bacteria can enter the body through the skin or mucous membranes (eyes, nose, mouth), particularly if the skin is broken or waterlogged. Transmission via animal bites and person-to-person transmission are rare.  

Leptospirosis is most commonly transmitted by water contaminated with urine, so outbreaks are often associated with heavy rainfall and flooding. Infection is particularly common among agricultural workers who are more likely to be exposed to infected rodents, livestock, and water sources. Other high-risk occupations include military personnel, veterinary staff, pest control, construction, and canal workers. Leptospirosis is also associated with water-based recreational activities including wild swimming and water sports.

Epidemiology

It is estimated that globally there are 1 million cases and 60,000 deaths caused by leptospirosis each year (CDC Yellow Book 2024). In Europe, there were 1,246 confirmed or suspected cases reported in 2021 and the burden was highest in Mediterranean and East European regions (ECDC Annual Epidemiological Report for 2021). There was a recent outbreak in Greece following Storm Daniel in 2023, which resulted in 5 confirmed and 17 probable cases.

In England, from 2020 to 2023 there were on average 57 laboratory-confirmed cases and 89 probable cases annually. Leptospirosis cases in England show seasonality with more cases reported in summer and autumn. Many cases diagnosed in England report exposure to potentially contaminated water or direct contact with rodents as the probable source of infection. Reported infections are most common in adult men, likely due to occupational and recreational exposures. However, infection can occur in anyone directly exposed to urine or urine-contaminated environments, regardless of age or sex.

For more information on the epidemiology of leptospirosis in England please see the Common animal-associated infections quarterly report.

For previous reports, see the health protection website archive.

Prevention and control

Increasing public awareness about the disease and preventative measures can help to reduce the risk of infection. These preventative measures include:

  • handwashing after contact with animals or exposure to water that might be contaminated with animal urine
  • cleaning wounds as soon as possible after exposure
  • showering as soon as possible after exposure
  • wearing protective clothing when appropriate
  • covering cuts and grazes with waterproof plasters
  • vaccinating domestic dogs against leptospirosis
  • avoiding contact with rodents and putting prevention and control measures in place where necessary
  • avoiding swimming and watersports in areas where contamination levels are high

There is no available vaccination against leptospirosis for humans.  

Vaccination against leptospirosis is available for cattle and dogs to prevent disease and reduce the risk of transmission to owners. In the UK it is part of the core vaccination programme for dogs. For further advice on preventing leptospirosis infection in cattle please see guidance published by APHA.

See the links below for guidance on how to prevent infection in specific settings:

Clinical features

Leptospirosis in humans has a wide range of clinical presentations. It may be subclinical in some, causes few or no symptoms, while in others it may cause a severe multi-systemic illness and sometimes death.

Symptoms of leptospirosis may include:

  • fever
  • headache
  • nausea and vomiting
  • inflammation of the eye (conjunctivitis, uveitis)

Features of severe infection include:

  • liver failure and jaundice
  • kidney failure
  • meningitis
  • pulmonary haemorrhage

Severe leptospirosis causing liver failure and jaundice is sometimes known as Weil’s disease. Infection may be biphasic, with an initial febrile illness which appears to improve before an acute deterioration.

Treatment is with antibiotics and supportive therapy.

NHS UK has further information on leptospirosis, including symptoms and prevention.

Leptospirosis diagnosis

The leptospirosis clinical diagnostic service is now provided by the Rare and Imported Pathogens Laboratory (RIPL) at UKHSA Porton. RIPL provide PCR testing for direct detection, and EIA testing for IgM. Testing is done Monday to Friday.

 The National Leptospirosis Service (NLS) at Colindale, and the Leptospira Reference Unit (LRU), Hereford, no longer exist.

Appropriate samples for leptospirosis diagnosis are blood and urine. Urine is particularly useful for leptospirosis as it remains PCR positive longer than blood samples. All diagnostic samples should be sent to RIPL with a leptospirosis request form. Precise information regarding the date of exposure and clinical features (symptoms, severity and onset) is important to ensure the appropriate initial tests are selected.

Leptospirosis is diagnosed by either:

  • PCR in the acute stage of infection, within 5 days of symptoms onset in blood, and longer in urine.
  • serological IgM detection (EIA) later in illness. This is performed on all samples of suspected leptospirosis cases.

Although there is occasional non-specific reactivity seen with the IgM, patients with a compatible syndrome and a positive leptospirosis IgM result should usually be treated on the basis of this result, even in the absence of a positive PCR result. It is good practice to send a repeat sample for confirmation of IgM in case of non-specific reactivity. Antibody cross-reactivity may be seen with syphilis, Lyme disease and legionella, however the clinical features of these diseases are usually sufficiently different so as not to cause confusion with leptospirosis.

IgM positive patients without a confirmatory PCR result are reported as probable cases for surveillance purposes.

Historically, leptospirosis confirmatory testing was performed using the microscopic agglutination test (MAT). However, a fit for purpose review in 2020 recommended cessation of the MAT service from 1 August 2020. PCR testing of acute samples is now the recommended method for leptospirosis diagnosis. 

Leptospirosis may also be identified on 16s PCR. Samples for 16s PCR testing should be sent to the Bacteriology Reference Department (BRD), UKHSA Colindale.

Hantavirus, associated with rat exposure, may present with a similar syndrome to leptospirosis. Testing is available at RIPL and may be performed on samples if the clinical information provide indicates a compatible clinical syndrome and risk factors, or if testing is specifically requested.

RIPL clinical staff are available to discuss cases with medical professionals during working hours.

Urgent clinical advice is available out of normal working hours by contacting either the on-call RIPL consultant or the Imported Fever Service (IFS). This service is for infection specialists only, and clinicians from other specialities should seek advice from their local infection services in the first instance.  

RIPL cannot provide advice directly to patients or the public.  If you are concerned that you have leptospirosis you are advised to seek advice through NHS services.

User manuals

See the Rare and Imported Pathogens Laboratory (RIPL) user manual

Contact

Rare and imported pathogens laboratory (RIPL) UK Health Security Agency
Manor Farm Road
Porton Down
Wiltshire
SP4 0JG

Email RIPL@ukhsa.gov.uk

Telephone 01980 612348 (available 9am to 5pm, Monday to Friday)

DX address DX 6930400, Salisbury 92 SP

Updates to this page

Published 15 July 2013
Last updated 20 August 2024 + show all updates
  1. Updated to reflect new testing process.

  2. Page updated regarding the completion of the pilot enhanced surveillance study.

  3. Added information on a pilot enhanced surveillance system.

  4. First published.

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