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Leptospirosis is a febrile disease (fever) caused by infection with the bacterium Leptospira interrogans. L. interrogans is sometimes classified as a spirochete because it has a spiral shape. The disease can range from very mild and symptomless to a more serious, even life threatening form, that may be associated with kidney (renal) failure.


An infection by the bacterium Leptospira interrogans goes by different names in different regions. Alternate names for leptospirosis include mud fever, swamp fever, cane cutter's fever, rice field fever, Stuttgart disease, swineherd's disease, and Fort Bragg fever. More severe cases of leptospirosis are called Weil's syndrome or icterohemorrhagic fever. This disease is commonly found in tropical and subtropical climates but occurs worldwide.
According to the Centers for Disease Control and Prevention (CDC), between 100 and 200 cases of leptospirosis are reported in the United States each year as of the early 2000s. Almost 75% of cases of leptospirosis in North America occur in males. About 50% of these cases occur in Hawaii, followed by the southern Atlantic, Gulf, and Pacific coastal states. However, because of the nonspecific symptoms of leptospirosis, it is believed that the occurrence in the United States is actually much higher. Leptospirosis occurs year-round in North America, but about half of the cases occur between July and October.
Leptospirosis is called a zoonosis because it is a disease of animals that can be transmitted to humans. It can be a very serious problem in the livestock industry. Leptospira bacteria have been found in dogs, rats, livestock, mice, voles, rabbits, hedgehogs, skunks, possums, frogs, fish, snakes, and certain birds and insects. Infected animals will pass the bacteria in their urine for months, or even years. In the United States, rats and dogs are more commonly linked with human leptospirosis than other animals.
Humans are considered accidental hosts and become infected with Leptospira interrogans by coming into contact with urine from infected animals. Transmission of the organism occurs either through direct contact with urine, or through contact with soil, water, or plants that have been contaminated by animal urine. Leptospira interrogans can survive for as long as six months outdoors under favorable conditions. Leptospira bacteria can enter the body through cuts or other skin damage or through mucous membranes (such as the inside of the mouth and nose). It is believed that the bacteria may be able to pass through intact skin, but this is not known.
Once past the skin barrier, the bacteria enter the blood stream and rapidly spread throughout the body. The infection causes damage to the inner lining of blood vessels. The liver, kidneys, heart, lungs, central nervous system, and eyes may be affected.
There are two stages in the disease process. The first stage is during the active Leptospira infection and is called the bacteremic or septicemic phase. The bacteremic phase lasts from three to seven days and presents as typical flu-like symptoms. During this phase, bacteria can be found in the patient's blood and cerebrospinal fluid. The second stage, or immune phase, occurs either immediately after the bacteremic stage or after a 1-3 day symptom-free period. The immune phase can last up to one month. During the immune phase, symptoms are milder but meningitis (inflammation of spinal cord and brain tissues) is common. Bacteria can be isolated only from the urine during this second phase.

Causes and symptoms

Leptospirosis is caused by an infection with the bacterium Leptospira interrogans. The bacteria are spread through contact with urine from infected animals. Persons at an increased risk for leptospirosis include farmers, miners, animal health care workers, fish farmers and processors, sewage and canal workers, cane harvesters, and soldiers. High-risk activities include care of pets, hunting, trail biking, freshwater swimming, rafting, canoeing, kayaking, and participating in sports in muddy fields. One recent outbreak occurred in Ireland following a canoe competition on a local river.
Symptoms of Leptospira infection occur within 7-12 days following exposure to the bacteria. Because the symptoms can be nonspecific, most people who have antibodies to Leptospira do not remember having had an illness. Eighty-five to 90% of the cases are not serious and clear up on their own. Symptoms of the first stage of leptospirosis last three to seven days and are: fever (100-105 °F [37.8-40.6 °C]), severe headache, muscle pain, stomach pain, chills, nausea, vomiting, back pain, joint pain, neck stiffness, and extreme exhaustion. Cough and body rash sometimes occur.
Following the first stage of disease, a brief symptomfree period occurs for most patients. The symptoms of the second stage vary in each patient. Most patients have a low-grade fever, headache, vomiting, and rash. Aseptic meningitis is common in the second stage, symptoms of which include headache and photosensitivity (sensitivity of the eye to light). Leptospira can affect the eyes and make them cloudy and yellow to orange colored. Vision may be blurred.
Ten percent of the persons infected with Leptospira develop a serious disease called Weil's syndrome. The symptoms of Weil's syndrome are more severe than those described above and there is no distinction between the first and second stages of disease. The hallmark of Weil's syndrome is liver, kidney, and blood vessel disease. The signs of severe disease are apparent after 3-7 days of illness. In addition to those listed above, symptoms of Weil's syndrome include jaundice (yellow skin and eyes), decreased or no urine output, hypotension (low blood pressure), rash, anemia (decreased number of red blood cells), shock, and severe mental status changes. Red spots on the skin, "blood shot" eyes, and bloody sputum signal that blood vessel damage and hemorrhage have occurred.


Leptospirosis can be diagnosed and treated by doctors who specialize in infectious diseases. During the bacteremic phase of the disease, the symptoms are relatively nonspecific. This often causes an initial misdiagnosis because many diseases have similar symptoms to leptospirosis. The later symptoms of jaundice and kidney failure together with the bacteremic phase symptoms suggest leptospirosis. Blood samples will be tested to look for antibodies to Leptospira interrogans. Blood samples taken over a period of a few days would show an increase in the number of antibodies. Isolating Leptospira bacteria from blood, cerebrospinal fluid (performed by spinal tap), and urine samples is diagnostic of leptospirosis. It may take six weeks for Leptospira to grow in laboratory media. Most insurance companies would cover the diagnosis and treatment of this infection.
Several diagnostic tests for leptospirosis have been devised in the early 2000s that are more accurate as well as faster than standard culture. One test uses flow cytometry light scatter analysis; this method can evaluate a sample of infected serum in as little as 90 minutes. A second technique is an IgM-enzyme-linked immunosorbent assay (ELISA), which detects the presence of IgM antibodies to L. interrogans in blood serum samples.


Leptospirosis is treated with antibiotics, penicillin (Bicillin, Wycillin), doxycycline (Monodox), ibramycin, or erythromycin (E-mycin, Ery-Tab). As of the early 2000s, however, many doctors prefer to treat patients with ceftriaxone, which is easier to use than intravenous penicillin. Ciprofloxacin may be combined with other drugs in treating patients who develop uveitis. It is generally agreed that antibiotic treatment during the first few days of illness is helpful. However, leptospirosis is often not diagnosed until the later stages of illness. The benefit of antibiotic treatment in the later stages of disease, however, is controversial. A rare complication of antibiotic therapy for leptospirosis is the occurrence of the Jarisch-Herxheimer reaction, which is characterized by fever, chills, headache, and muscle pain.
Patients with severe illness will require hospitalization for treatment and monitoring. Medication or other treatment for pain, fever, vomiting, fluid loss, bleeding, mental changes, and low blood pressure may be provided. Patients with kidney failure will require hemodialysis to remove waste products from the blood.


The majority of patients infected with Leptospira interrogans experience a complete recovery. Ten percent of the patients will develop eye inflammation (uveitis) up to one year after the illness. In the United States, about one out of every 100 patients will die from leptospirosis. Death is usually caused by kidney failure, but has also been caused by myocarditis (inflammation of heart tissue), septic shock (reduced blood flow to the organs because of the bacterial infection), organ failure, and/or poorly functioning lungs. Mortality is highest in patients over 60 years of age.


Persons who are at an extremely high risk (such as soldiers who are training in wetlands) can be pretreated with 200 mg of doxycycline once a week. As of the early 2000s, there are no vaccines available to prevent leptospirosis in humans, although such vaccines have been formulated by veterinarians for dogs, swine, and cattle.
There are many ways to decrease the chances of being infected by Leptospira. These include:
  • Avoid swimming or wading in freshwater ponds and slowly moving streams, especially those located near farms.
  • Do not conduct canoe or kayak capsizing drills in freshwater ponds. Use a swimming pool instead.
  • Boil or chemically treat pond or stream water before drinking it or cooking with it.
  • Control rats and mice around the home.
  • Have pets and farm animals vaccinated against Leptospira.
  • Wear protective clothing (gloves, boots, long pants, and long-sleeved shirts) when working with wet soil or plants.



Beers, Mark H., MD, and Robert Berkow, MD., editors. "Infectious Diseases Caused by Spirochetes." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.


Boland, M., G. Sayers, T. Coleman, et al. "A Cluster of Leptospirosis Cases in Canoeists following a Competition on the River Liffey." Epidemiology and Infection 132 (April 2004): 195-200.
Faucher, J. F., B. Hoen, and J. M. Estavoyer. "The Management of Leptospirosis." Expert Opinion in Pharmacotherapy 5 (April 2004): 819-827.
Vitale, G., C. La Russa, A. Galioto, et al. "Evaluation of an IgM-ELISA Test for the Diagnosis of Human Leptospirosis." New Microbiologica 27 (April 2004): 149-154.
Yitzhaki, S., A. Barnea, A. Keysary, and E. Zahavy. "New Approach for Serological Testing for Leptospirosis by Using Detection of Leptospira Agglutination by Flow Cytometry Light Scatter Analysis." Journal of Clinical Microbiology 42 (April 2004): 1680-1685.


American Veterinary Medical Association (AVMA). 1931 North Meacham Road, Suite 100, Schaumburg, IL 60173-4360. http://www.avma.org.
Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.

Key terms

Hemodialysis — The removal of waste products from the blood stream in patients with kidney failure. Blood is removed from a vein, passed through a dialysis machine, and then put back into a vein.
Jarisch-Herxheimer reaction — A rare reaction to the dead bacteria in the blood stream following antibiotic treatment.
Meningitis — Inflammation of tissues in the brain and spinal cord. Aseptic meningitis refers to meningitis with no bacteria present in the cerebral spinal fluid.
Spirochete — Any of a family of spiral- or coil-shaped bacteria known as Spirochetae. L. interrogans is a spirochete, as well as the organisms that cause syphilis and relapsing fever.
Zoonosis (plural, zoonoses) — Any disease of animals that can be transmitted to humans. Leptospirosis is an example of a zoonosis.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


any of a group of infectious diseases due to certain serotypes of Leptospira. The best known is weil's disease (called also leptospiral jaundice); others are mud fever (called also autumn fever) and swineherd's disease. The etiologic agent is a spiral organism that infects the kidneys of cattle, swine, dogs, cats, rats, and other animals. The organisms are spread through the animals' urine. The portal of entry is usually through abrasions. The disease is most common among people who handle infected animals or the kidneys and other infected tissues of such animals.
Symptoms. Leptospirosis is usually a short illness that produces a variety of symptoms. It begins with fever, acute headache, chills, and sometimes nausea and vomiting. Later, other symptoms may be caused by the effects of the disease upon the kidneys, liver, skin, blood, and other organs. These symptoms can include jaundice, skin rashes, hemorrhages of the skin and mucous membranes, inflammation of the eye, hematuria, and oliguria.

Diagnosis is often difficult because the symptoms resemble those of several other diseases. Jaundice is a key symptom that, when present, aids in diagnosis.

Most cases are mild, consisting only of the early symptoms and having a duration of 1 to 2 weeks. In a few cases, a severe infection may cause damage to the kidneys, liver, or heart. Only rarely is the disease fatal.
Treatment and Prevention. The treatment of choice is doxycycline. Sanitation measures can reduce the spread of the disease in humans and other animals. Vaccines for animals are available, but provide only partial immunity to the disease. At the present time there are no vaccines of established value for human beings.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Infection with Leptospira interrogans.
Farlex Partner Medical Dictionary © Farlex 2012


An infectious disease of domestic animals, humans, and other mammals, characterized by fever and jaundice and caused by spirochetes of the genus Leptospira, which are transmitted to humans by contact with the urine of infected animals.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Icterohemorrhagic fever, Weil's disease Tropical disease Infection with Leptospira spp–eg, Leptospira canicola serotype canicola, which may follow ingesting water contaminated by infected livestock, rodent urine Clinical Bleeding, jaundice, pulmonary hemorrhage, pulmonary edema
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


An acute infectious disease caused by a spirochete, Leptospira interrogans; infection is zoonotic and distributed worldwide.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


An infection caused by a fine spiral-shaped organism (SPIROCHAETE) Leptospira icterohaemorrhagiae or L. canicola and transmitted in the urine of rats or dogs to farm and veterinary workers, fish-market workers, sewer workers and miners. The organism can penetrate the intact skin and the infection may be mild. Severe cases feature headache, muscle aches and tenderness, red eyes, loss of appetite, vomiting and sometimes a skin rash. JAUNDICE, HEART FAILURE and MENINGITIS may occur and are signs of danger. The mortality in such cases may be as high as 20%. Those who recover do so completely. The organisms are sensitive to penicillin and this drug is effective, if given early. Also knows as Weil's disease. (H. Adolph Weil, German physician, 1848–1916).
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Generally, anicteric leptospirosis and icteric leptospirosis are the two types of infections that illustrate different signs and symptoms (5).