Leptospirosis (lep’to-spi-ro´sis) is a bacterial disease caused by the genus Leptospira. It is considered the most common zoonosis in the world.
Origin: Leptospirosis was first recognized as an occupational disease of sewer workers in 1883. Weil described its clinical symptoms in 1886, and Inada of Japan identified the causal agent in 1916.
Symptoms: Some infected persons may have no symptoms at all, but in others symptoms may include high fever, severe headache, chills, muscle aches, vomiting, jaundice (yellow skin and eyes), red eyes, abdominal pain, diarrhea, and rash. If left untreated, the patient could develop kidney damage, meningitis, liver failure, and/or respiratory distress. In rare cases, death occurs.
Differential Diagnosis: Dengue Fever, Encephalitis, Hantavirus Cardiopulmonary Syndrome, Hepatitis, Malaria, Meningitis, Mononucleosis, Rickettsial Disease, Typhoid Fever.
Transmission: Leptospirosis is usually contracted by exposure to water contaminated with the urine of infected animals, many of which may carry the bacterium. The leptospira organisms have been found in cattle, pigs, horses, dogs, rodents, and wild animals. The most important reservoirs are rodents, and rats are the most common source worldwide. In the United States, important leptospiral sources include dogs, livestock, rodents, wild animals, and cats. Humans become infected through contact with water, food, or soil containing urine from infected animals. This may happen by swallowing contaminated food or water, or through skin contact, especially with mucosal surfaces, such as the eyes or nose, or with broken skin. Occasionally, the organism may even enter the body through intact skin. The disease is not known to be spread from person to person.
Incubation: Sickness can occur as early as two days, or as long as four weeks following exposure. The patient may appear to recover for a time and then become ill again. If a second phase occurs, it is usually more severe than the first phase; the person may have kidney or liver failure or meningitis. This phase is also called Weil’s disease.
Duration: The illness caused by leptospirosis may last from a few days to three weeks or longer. Without treatment, recovery may take several months.
Treatment: Leptospirosis is treated with antibiotics, such as doxycycline or penicillin, which should be given early in the course of the disease. Intravenous antibiotics may be required for persons with more severe symptoms.
Geographic Range: Leptospirosis occurs worldwide but is most common in temperate or tropical climates. The leptospires from infected animals survive best in freshwater, damp alkaline soil, vegetation, and mud with temperatures higher than 22°C.
Incidence: It is an occupational hazard for many people who work outdoors or with animals and this population accounts for 30% to 50% of human cases. Those at risk include wildlife professionals, farmers, sewer workers, veterinarians, fish workers, and military personnel. It is a recreational hazard for campers and those who participate in outdoor sports in contaminated areas and it has been associated with swimming, wading, and whitewater rafting in contaminated lakes and rivers. The incidence is also increasing among urban children. Except in areas where outbreaks have occurred, such as Hawaii in 2004, there are generally fewer than 100 cases reported in the United States annually. Massive outbreaks have occurred recently in Nicaragua (1995), and in Thailand (2000).
Prevention: The risk of acquiring leptospirosis can be greatly reduced by avoiding water that might be contaminated with animal urine. Protective clothing or footwear should be worn by those exposed to contaminated water or soil because of their job or recreational activities.
Sources: CDC, Medscape.com, and Vetmed.wisc.edu.
NOTE: The International Leptospirosis Society (ILS) was formed in 1994 to promote knowledge on leptospirosis through the organisation of regional and global leptospirosis meetings. For free membership and information go to < http://www.med.monash.edu.au/microbiology/staff/adler/ils.html > .