Leptospirosis

Unique identifier / Notation

BI0217

Synonyms

Weil's disease Weil-Vasiliev disease Swineherd's disease rice-field fever waterborne fever nanukayami fever cane-cutter fever swamp fever mud fever Stuttgart disease Canicola fever

Leptospirosis is an infectious disease caused by a pathogenic bacterium of the genus Leptospira. These bacteria called leptospires affect both humans and animals. Humans become infected through direct contact with the urine of infected animals or with a urine-contaminated environment which can lead to serious and sometimes fatal disease (adapted from WHO & ILS, 2003).

Primary reference(s)

WHO and ILS, 2003. Guidance for Diagnosis, Surveillance and Control. World Health Organization (WHO) and International Leptospirosis Society (ILS). Accessed 29 November 2024.

Annotations

Additional scientific description

Human

Leptospires are bacteria which can be either pathogenic (i.e., having the potential to cause disease in animals and humans) or saprophytic (i.e., free-living and generally considered not to cause disease (WHO SEARO, no date a).

Pathogenic leptospires are maintained in nature in the renal tubules of certain animals. Saprophytic leptospires are found in many types of wet or humid environments ranging from surface waters and moist soil to tap water. Saprophytic halophilic (salt-loving) leptospires are found in seawater (WHO & ILS, 2003).

Humans usually acquire leptospirosis through direct contact with the urine of infected animals or a urine-contaminated environment. Human-to-human transmission occurs only very rarely. The bacteria enter the body through cuts or abrasions on the skin, or the mucous membranes of the mouth, nose and eyes. (WHO, no date a).

Leptospirosis occurs worldwide but is most common in tropical and subtropical areas with high rainfall. Leptospirosis is a disease of epidemic potential, especially after heavy rainfall or flooding. Cases have been reported in most countries of the Americas and outbreaks have been reported in Brazil, Nicaragua, Guyana and several other Latin American countries. The majority of reported cases have severe manifestations, for which mortality is greater than 10%. Outbreaks can be associated with floods and hurricanes (WHO, no date b).

Animal

Leptospira is globally enzootic, but the disease is more frequently seen in warm and moist environments. Leptospira serovars are known to cause disease in mammals and have been isolated from amphibians. Some serovars have also been isolated from invertebrates, reptiles, and birds. A variety of Leptospira vaccines are available for domestic animals, including livestock. Most countries maintain a list of approved veterinary vaccines for use. For specific regulations, consult the country's veterinary authorities. Virtually all mammals are vulnerable to pathogenic Leptospira serovars to varying degrees. In incidental hosts, a serious disease with high tissue burdens and robust antibody responses can be seen (WOAH, 2020).

Metrics and numeric limits

Case-fatality rates in different parts of the world have been reported to range from <5% to 30%. These figures are not reliable because in many areas the occurrence of the disease is not well documented. In addition, mild cases may not be diagnosed as leptospirosis (WHO & ILS, 2003).

It is estimated that 0.1 to 1 per 100,000 people living in temperate climates are affected each year, with the number increasing to 10 or more per 100,000 people living in tropical climates. If there is an epidemic, the incidence can soar to 100 or more per 100,000 people. (WHO & ILS, 2003).

Cases have been reported in most countries of the Americas and outbreaks have been reported in Brazil, Nicaragua, Guyana and several other Latin American countries. The majority of reported cases have severe manifestations, for which mortality is greater than 10%. The number of human cases is not known precisely due to under- or misdiagnosis (PAHO, no date).

Key relevant UN convention / multilateral treaty

International Health Regulations (2005), 3rd ed. (WHO, 2016).

Drivers

Human

Leptospirosis can also be an occupational hazard for people who work outdoors or with animals, such as rice and sugarcane field workers, farmers, sewer workers, veterinarians, dairy workers, and military personnel. It is also a recreational hazard to those who swim or wade in contaminated water (WHO, no date b).

Leptospirosis is overlooked and under-reported for many reasons including difficulty in distinguishing clinical signs from those of other endemic diseases and lack of appropriate diagnostic laboratory services (WHO, 2003).

Animal

Warm and moist environments, exposure to contaminated water

Impacts

Human

In the early stages of the disease, symptoms include high fever, severe headache, muscle pain, chills, redness of the eyes, abdominal pain, jaundice, haemorrhages in the skin and mucous membranes, vomiting, diarrhoea, and rash (WHO & ILS, 2003).

The clinical manifestations are highly variable. Typically, the disease presents in four broad clinical categories: a mild, influenza-like illness; Weil’s syndrome characterised by jaundice, renal failure, haemorrhage and myocarditis with arrhythmias; meningitis/meningoencephalitis; and pulmonary haemorrhage with respiratory failure (Yang, 2007).

Clinical diagnosis is difficult because of the varied and non-specific presentation. Confusion with other diseases, such as dengue and other haemorrhagic fevers, is particularly common in the tropics. It may present with a wide variety of clinical manifestations ranging from a mild flu-like illness to a serious and sometimes fatal disease. Icterus (jaundice) is a relatively common symptom in leptospirosis but is also found in many other diseases involving the liver such as the various forms of hepatitis (WHO SEARO, no date; WHO & ILS, 2003).

Major improvements in the prognosis of severe leptospirosis have been made in recent decades, owing to the use of haemodialysis as a means of supporting the reversible renal failure that may occur in some cases and to aggressive supportive care (WHO & ILS, 2003).

Animal

Varies by serovar

Multi-hazard context

Leptospirosis is endemic in many countries, across the world. It often has a seasonal distribution, increasing with increased rainfall or higher temperature. However, the disease can occur throughout the year. High risk of exposure can be related to occupation, the environment or lifestyle choices. Epidemics may be associated with changes in human behaviour, animal or sewage contamination of water in paddy and sugarcane plantations, changes in animal reservoir density, or following natural hazards such as cyclones, hurricanes, heavy rainfall or floods. The main occupational groups at risk include farm and agricultural workers, pet shop workers, veterinarians, sewer workers, abattoir workers, meat handlers, and the military. It is also a recreational hazard to those who swim or wade in contaminated water. A variety of animal hosts have been identified, including rodents, livestock, and other domestic animals while humans serve as incidental hosts. Wild and domestic animals in the carrier state may shed leptospires intermittently for many years or even a lifetime (PAHO, no date; WHO SEARO, no date a).

Risk Management

Human

During floods, leptospirosis risk increases due to contaminated floodwater containing animal urine, especially from rodents. Communication with at-risk individuals should focus on preventing contact with contaminated water, emphasizing caution during and after floods. This includes avoiding wading, swimming, or playing in floodwater, as well as avoiding contact with contaminated soil or mud (WHO, 2023b).

The World Health Organization (WHO) has set several goals concerning leptospirosis: to provide estimates of the global burden of leptospirosis according to age, sex and region, to increase awareness of and commitment to the disease in developing countries; and to encourage developing countries to undertake active disease surveillance and strengthen control measures (WHO, 2011).

These efforts will ultimately enable policymakers and other stakeholders to translate knowledge into policy by setting appropriate evidence-based priorities in the area of leptospirosis disease control and prevention.

To coordinate and direct global research and action against human leptospirosis, the WHO has established the Leptospirosis Burden Epidemiology Reference Group (LERG). It has been assigned the following tasks: to review and appraise epidemiological evidence based on commissioned reviews and studies; to develop epidemiological tools to estimate disease burden; to estimate and express disease burden through summary measures of population health (including disability-adjusted life years); and to identify technical gaps for research (WHO, 2011).

The WHO Secretariat for the LERG is based at the Department of Food Safety and Zoonoses with functions of facilitating, coordinating, guiding and monitoring the work of the LERG. The LERG also partners with other international actors including the Global Burden of Disease (GBD 2005) initiative coordinated by the Institute for Health Metrics and Evaluation (WHO, 2011).

Animal

Biosecurity

Monitoring

The section and the table below offer an overview of monitoring for leptospirosis. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management.

Which institution(s) produce(s) Disaster Risk Data/Information?  

Ministry of Health, Ministry of Agriculture, Ministry of Livestock, FAO Reference Centres, WOAH Reference Laboratories, WHO

How is the Hazard Observed/Monitored/Forecast?  

WHO supports countries to conduct all-hazards strategic risk assessment in the contexts of health emergencies and disasters, which results in the development of a country's risk profile. Empowered with the country risk profile, inclusive of a seasonal risk calendar, countries can anticipate potential emergencies before they occur to trigger early alerts and inform early actions (WHO, 2021).

WHO's Early Warning, Alert and Response System (EWARS) has been designed to improve disease outbreak detection in emergency settings, such as in countries in conflict or following a natural disaster. It is a simple and cost-effective way to rapidly set up a disease surveillance system. EWARS is deployed during an emergency as an adjunct to the national disease surveillance system. WHO works with Ministries of Health and health sector partners to train local health workers to use the system. After the emergency, EWARS should re-integrate back into the national system (WHO, 2023a).

Through its global early warning system, FAO has been supporting Members with risk monitoring, assessment and forecasting for animal health threats to enhance preparedness and response to animal health threats:

The Global Animal Disease Information System, EMPRES-i+, plays a crucial role in supporting countries with early warning and early detection of animal disease outbreaks. By providing a comprehensive platform for real-time disease tracking, EMPRES-i+, enables monitoring and analysis of animal health threats effectively, collaborating closely with countries and regions on disease information sharing. This supports the dissemination of risk assessments and alerts for evidence-based decision-making.
FAO develops and maintains decision support tools that provide risk maps of existing and predicted risks of animal disease emergence, as well as other threats to the agri-food chain.
Additionally, FAO collaborates closely with international organizations like WHO and WOAH to verify disease information through integrated mechanisms such as the Epidemic Intelligence from Open Sources (EIOS), the Global Early Warning System (GLEWS+), and the World Animal Health Information System (WAHIS) for WOAH-listed diseases. These collaborations allow for the dissemination of early warning alerts and risk assessments to Members, to enable timely responses to potential outbreaks.

FAO empres-i+ https://empres-i.apps.fao.org/diseases   

WOAH WAHIS https://wahis.woah.org/#/event-management  