Leptospirosis is a bacterial disease that affects both humans and animals. Humans become infected through direct contact with the urine of infected animals or with a urine-contaminated environment. The bacteria enter the body through cuts or abrasions on the skin, or through the mucous membranes of the mouth, nose and eyes. Person-to-person transmission is rare.
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.
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ZOONOSIS
A zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans. Animals thus play an essential role in maintaining zoonotic infections in nature. Zoonoses may be bacterial, viral, or parasitic, or may involve unconventional agents. As well as being a public health problem, many of the major zoonotic diseases prevent the efficient production of food of animal origin and create obstacles to international trade in animal products.
Leptospirosis is an infection in rodents and other wild and domesticated species. Rodents are implicated most often in human cases. The infection in man is contracted through skin abrasions and the mucosa of the nose, mouth and eyes. Exposure through water contaminated by urine from infected animals is the most common route of infection. Human-to-human transmission is rare.
Outdoor and agricultural workers (rice-paddy and sugarcane workers for example) are particularly at risk but it is also a recreational hazard to those who swim or wade in contaminated waters. In endemic areas the number of leptospirosis cases may peak during the rainy season and even may reach epidemic proportions in case of flooding because the floods cause rodents to move into the city.
Prevention strategies of human leptospirosis include wearing protective clothing for people at occupational risk and avoidance of swimming in water that may be contaminated. Leptospirosis control in animals is dependent on the serovar and animal species but may be either vaccination, a testing a culling programme, rodent control or a combination of these strategies.
Surveillance
The attached excerpt provides WHO recommended standards and strategies for the surveillance, prevention and control of Leptospirosis. This section is part of a larger document entitled "WHO recommended standards and strategies for surveillance, prevention and control of communicable diseases " developed by the WHO Emerging Diseases and Pandemic Response Department (EPR), in collaboration with the Department Food Safety and Zoonoses (FOS), for major zoonoses involving livestock. Each section, after giving essential information on the main characteristics of the disease and its causative agent(s) and mode of transmission, provides definitions for possible, probable and definite cases of the disease as well as the rational for surveillance and WHO recommended systems for surveillance. Major control and prevention activities in humans and animal hosts are also described. A list of WHO reference materials is provided at the end.
Water-related Diseases
Leptospirosis
The disease and how it affects people
Leptospirosis is a bacterial disease that affects both humans and animals. The early stages of the disease may include high fever, severe headache, muscle pain, chills, redness in the eyes, abdominal pain, jaundice, haemorrhages in skin and mucous membranes (including pulmonary bleeding), vomiting, diarrhoea and a rash.
The cause
Pathogenic Leptospira spp. cause leptospirosis. Human infection occurs through direct contact with the urine of infected animals or by contact with a urine-contaminated environment, such as surface water, soil and plants. The causative organisms have been found in a variety of both wild and domestic animals, including rodents, insectivores, dogs, cattle, pigs and horses. Leptospires can gain entry through cuts and abrasions in the skin and through mucous membranes of the eyes, nose and mouth. Human-to-human transmission occurs only rarely.
Distribution
Leptospirosis occurs worldwide, in both rural and urban areas and in temperate and tropical climates. It is an occupational hazard for people who work outdoors or with animals, such as rice and sugar-cane 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 waters. In endemic areas the number of leptospirosis cases may peak during the rainy season and even may reach epidemic proportions in case of flooding.
Scope of the Problem
The number of human cases worldwide is not well-documented. It probably ranges from 0.1 to 1 per 100 000 per year in temperate climates to 10 or more per 100 000 per year in the humid tropics. During outbreaks and in high-risk groups, 100 or more per 100 000 may be infected. For several reasons leptospirosis is overlooked and consequently underreported in many areas of the world. In the wake of hurricane Mitch in 1995, an outbreak of leptospirosis with pulmonary haemorrhages was reported in Nicaragua. In 1998, there was an outbreak in the continental United States. 1998 also saw an outbreak in Peru and Ecuador following heavy flooding. A post-cyclone outbreak was reported in Orissa, India in 1999.
Interventions
The disease is often difficult to diagnose clinically; laboratory support is indispensable. Treatment with appropriate antibiotics should be initiated as early as possible. Untreated cases can progress to a more severe and potentially fatal stage. Preventive measures must be based on a knowledge of the groups at particular risk of infection and the relevant local epidemiological factors. For intervention one may:
· aim at control at the level of the infection source (e.g. rodent control, animal vaccination);
· interrupt the transmission route (e.g. wearing protective clothing, refrain from contact with infected animals and from swimming in contaminated water, provide clean drinking-water); or
· prevent infection or disease in the human host (e.g. vaccination, antibiotic prophylaxis, information to doctors, veterinarians, risk groups and the general population).
Prepared for World Water Day 2001. Reviewed by staff and experts from the cluster on Communicable Diseases (CDS) and Water, Sanitation and Health unit (WSH), World Health Organization (WHO).
