Photo Credits: O. Chavez, Nicaragua
Leptospirosis is a zoonotic disease with epidemic potential, especially after heavy rainfall. It occurs throughout the world and is emerging as an important public health problem in both tropical and subtropical countries, affecting mostly vulnerable populations (WHO 2010; WHO 2011). Humans usually acquire leptospirosis through direct contact with the urine of infected animals or a urine-contaminated environment. 
Leptospira sp. Photo Credits: CDC Public Health Image Library - Janice Haney Carr
Leptospira interrogans is pathogenic to humans and animals, with more than 200 serologic variants or serovars (WHO, 2003). A wide variety of animal species, both wild and domestic, can serve as sources of infection for humans (Acha, 2003). The species that are considered to be the most important include feral and peridomestic rodents (rats, mice, voles, etc.) and domestic animals (cattle, pigs, dogs and horses). Human-to-human transmission occurs very rarely.  

Photo Credits: O. Chavez, Nicaragua

Leptospirosis may present as a mild illness that may progress to a more serious and sometimes fatal disease. It has a wide variety of clinical manifestations; in its mild form it may mimic many other diseases such as influenza and dengue, which are endemic in many countries of the Americas. It is important to make the correct diagnosis (clinical and laboratory) at the onset of symptoms in order to prevent severe cases and save lives, primarily in outbreak situations. -- Read more about symptoms and diagnosis.

Previous estimates indicate that there are more than 500,000 cases of leptospirosis each year worldwide. The majority of reported cases have severe manifestations, for which mortality is greater than 10% (WHO 2010). The global burden of disease is being estimated by the Leptospirosis Burden Epidemiology Reference Group (LERG), coordinated by the WHO and partners.
Reglamento Sanitario InternacionalSince the implementation of the revised version of the International Health Regulations (IHR), which was enacted in June 2007, events considered as a potential public health emergency of international concern (PHEIC) are recorded by the Events Management System (EMS), that supports the IHR. Leptospirosis is among the top 10 events of infectious nature reported in the EMS globally ("top 10 infectious hazard"); confirming the importance of this disease as a potential threat to public health (Figure 1). For the Region of the Americas, a study conducted by PAHO shows that 70% of PHEIC occur in the animal/human health interface, which includes outbreaks of leptospirosis (Schneider, 2011).

Figure 1. Main events of infectious nature recorded in the global event management site of the International Health Regulations, June 2007 to December 2011

Figure 1. Main events of infectious nature recorded in the global event management site of the International Health Regulations, June 2007 to December 2011

Photo Credits: G. Moreno, Nicaragua

The Region of the Americas has presented the vast majority of alerts for leptospirosis in recent years. Reviewing the HealthMap database that utilizes different online sources for real-time surveillance of emerging public health threats, 568 alerts for leptospirosis were found between 2007 and 2011 worldwide. More than half of them were located in the Americas, particularly in Brazil (140 alerts), Nicaragua (53), the Dominican Republic (28) and Honduras (19) (HealthMap, accessed on Fecruary 2012).

These countries subsequently met in Nicaragua in August 2012 for the "National Forum of Leptospirosis of Nicaragua" and the "International Meeting of Countries that are Facing Outbreaks of Leptospirosis in the Americas", in order to share their experiences, present recent research findings and discuss ways to move forward to predict, detect, prevent and respond to outbreaks of leptospirosis. Following up the recommendations of the Global Leptospirosis Environmental Action Network (GLEAN), coordinated by the WHO and partners.

Photo Credits: O. Chavez, Nicaragua

Cases occur in smaller numbers throughout the year in most countries of the Region, many of these related to occupation (e.g. rice field, sewer and slaughterhouse workers) and other methods of contact with contaminated soil or water (e.g. personal or recreational use). Since leptospirosis is a zoonosis with a complex transmission cycle involving different species of domestic and wild animals, as well as environmental factors, a multidisciplinary and intersectoral approach is necessary for its understanding and coordinated actions (WHO 2010; WHO 2011; GLEAN). Collaboration between sectors and institutions is needed to address health risks in the human-animal-ecosystem interface in order to achieve successful and sustainable results (FAO-OIE-WHO, 2010). Leptospirosis can be considered a good example of the framework for "One Health", where an integrated approach between public health, animal health and the environment is the foundation to prevent, detect, respond and control diseases common to man and animals (FAO-OIE-WHO, 2008; FAO-OIE-WHO, 2004). 

Related Links:

:: WHO. Health Topics - Leptospirosis

:: WHO. Zoonoses - Leptospirosis

:: Global Leptospirosis Environmental Action Network (GLEAN)

:: WHO. International Health Regulations (English); (Spanish)

:: HealthMap 


:: WHO. Report of the First Meeting of the Leptospirosis Burden Epidemiology Reference Group (LERG), 2010. (En inglés)

:: WHO. Report of the Second Meeting of the Leptospirosis Burden Epidemiology Reference Group (LERG), 2011. (En inglés)

:: WHO. Human leptospirosis: Guidance for diagnosis, surveillance, and control, 2003. (English); (Español)

:: OPS. Salud en las Américas, 2012 (English); (Español)

:: Acha PN et al. Zoonosis y enfermedades transmisibles comunes al hombre y a los animales, 2003. (English); (Español)

:: The FAO-OIE-WHO Collaboration: Sharing responsibilities and coordinating global activities to address health risks at the animal-human-ecosystems interfaces.

:: FAO-OIE-WHO. Contributing to One World, One Health - A Strategic Framework for Reducing Risks of Infectious Diseases at the Animal-Human-Ecosystems Interface.

:: Report of the WHO/FAO/OIE joint consultation on emerging zoonotic diseases.

:: Schneider MC et al. Importance of animal/human health interface in potential Public Health Emergencies of International Concern in the Americas. Re Panam Salud Publica. 2011.

:: Reis RB et al. Impact of environmental and social gradient on Leptospira infection in urban slums. PLoS Neglect. Trop. D., 2008.

:: Liverpool J et al. Leptospirosis: case reports of an outbreak in Guyana, Am Trop Med Parasitol, 2008.

:: Ko AI et al. The Salvador Leptospirosis Study Group. Urban epidemic of severe leptospirosis in Brazil. Lancet, 1999.

:: Schneider MC et al. Leptospirosis outbreaks in Nicaragua: identifying critical areas and exploring drivers for evidence-based planning. Int. J. Environ. Res. Public Health, 2012.

:: Costa, F. et al. Surveillance for leptospirosis in the Americas, 1996-2005: a review of data from ministries of health. Rev Panam Salud Publica 32(3), 2012.