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.
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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〉.
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.
Leptospirosis is a disease that is caused by bacteria from the genus Leptospira. It is considered an emerging disease and is found worldwide. Leptospirosis often goes undiagnosed, since the symptoms of this disease are similar to those of a number of other diseases, including influenza. For this reason, the prevalence of the disease is unknown.
Infection occurs when humans come in contact with freshwater, soil, or vegetation that is contaminated with the urine of an infected animal. The bacteria pass from the urine into the human body via mucosal linings, such as the linings of the eyes, nose, or mouth; through broken skin; or orally, when food or water is ingested. Illness develops, usually within 10 days, and is characterized by fever, aches, vomiting, diarrhea, and jaundice. Treatment with antibiotics leads to successful recovery, although, in some cases, a second phase can occur with more severe symptoms. During this second phase, known as Weil's disease, patients suffer more severe symptoms that may include kidney failure, liver failure, or meningitis. Weil's disease occurs in around 10% of cases.
Leptospirosis occurs mainly in the tropics, although it is a worldwide disease found both in rural and urban regions of developed and developing countries. There is no vaccine for this disease, and prevention efforts focus on avoiding contact with anything that may have been contaminated with the bacteria. Risk is highest for people who work or spend time outdoors, in freshwater, or with animals.
Leptospirosis was first recognized in 1886 by the German scientist Adolf Weil (1848–1916). The cause of the disease was not identified until about 40 years later, during the 1920s, when both Japanese and German scientists discovered that bacteria were responsible. Leptospirosis is caused by leptospires, which are diseasecausing bacteria in the genus Leptospira. The primary agent causing leptospirosis is Leptospira interrogans.
Leptospirosis most commonly occurs in the tropics, although it is present in temperate regions. Leptospires thrive best in warm temperatures and moist conditions. They are transmitted by wild and domestic animals including rodents, dogs, cattle, horses, and pigs. Therefore, people who spend a great deal of time outdoors, or with animals, are more likely to contract leptospirosis. This includes veterinarians, military personnel, farmers, and sewer workers. In addition, people taking part in outdoor recreational activities, such as camping or water sports, are also at higher risk, since they are more likely to come in contact with urine-contaminated water.
Leptospirosis occurs worldwide but tends to be underreported in most countries, since it is often overlooked during diagnosis. This is due to the similarities between symptoms of leptospirosis and those of other tropical diseases. As a result, the global prevalence of this disease is unknown. However, increases in the occurrence of this disease were observed in Germany between 1962 and 2003. These increases are thought to be a result of more frequent travel, increases in freshwater recreational activities, and higher rat populations in cities.
WORDS TO KNOW
JAUNDICE: Jaundice is a condition in which a person's skin and the whites of the eyes are discolored a shade of yellow due to an increased level of bile pigments in the blood resulting from liver disease. Jaundice is sometimes called icterus, from a Greek word for the condition.
LEPTOSPIRE: Also called a leptospira, a leptospire is any bacterial species of the genus Leptospira. Infection with leptospires causes leptospirosis.
WEIL'S DISEASE: Weil's disease, named after German doctor Adolf Weil (1848–1916), is a severe form of leptospirosis or seven-day fever, a disease caused by infection with the corkscrew-shaped bacillus Leptospira interrogans.
Patients with leptospirosis can recover without treatment, although recovery may take several months, and lack of treatment may lead to complications. Treatment is usually administered as soon as possible and involves a course of antibiotics. A range of antibiotics can be used, including doxycycline, penicillin, ampicillin, and amoxicillin. Recovery can take from three days to several weeks. However, in most cases recovery is complete. More severe complications arise when the patient does not receive antibiotics or if the patient develops the second phase of the illness.
There is no vaccine for leptospirosis, so prevention is best achieved by avoiding contaminated water, soil, or vegetation, particularly in areas with infected or potentially infected animals. Clothing, such as boots or waders, will provide protection during recreational activities, and gloves will provide protection when handling animals. Taking antibiotics while traveling through infected areas may also help prevent severe infections from developing, if people become contaminated.
Leptospirosis is becoming more common and has been recognized as an emerging infectious disease by the United States Directors of Health Promotion and Education. Since this disease occurs in both developed and developing countries and in both urban and rural areas, it has become globally important.
Despite the high likelihood of recovery following treatment, there is still a significant mortality rate for leptospirosis. This is largely due to delayed diagnosis, since the disease is hard to recognize. In addition, due to the lack of a vaccine, avoidance of the bacteria remains the best prevention method. This avoidance depends on the maintenance of rigorous sanitation methods, which is not always possible in developing countries or in countries experiencing war or other social upheavals. Therefore, contamination still occurs frequently.
The chance of exposure to contaminated sources is exacerbated during floods, outdoor activity, or in animal-populated regions. In 1995, widespread flooding in Nicaragua spread the bacteria, and more than 2,000 people contracted leptospirosis. At least 13 of those with the disease died. Two years later, nine Americans became infected while white-water rafting in Costa Rica. In addition, growing rat populations, especially in inner cities, increase public exposure to leptospirosis when water systems and sewers become contaminated. This has been suggested as one cause of the higher levels of leptospirosis seen in Germany during 1962–2003.
IN CONTEXT: PERSONAL RESPONSIBILITY AND PROTECTION
As of April 2007, the CDC states that “No vaccine is available to prevent leptospirosis in the United States. Travelers who might be at an increased risk for the disease should be advised to consider preventive measures such as wearing protective clothing and minimizing contact with potentially contaminated water. Such travelers also might benefit from chemoprophylaxis (a course of treatment prior to exposure that reduces risk or impact of disease). Until further data become available, CDC recommends that travelers who might be at increased risk for leptospirosis be advised to consider chemoprophylaxis begun 1 to 2 days before exposure and continuing through the period of exposure.”
Individuals should always seek advice from their personal physician with regard to specific medications and doses.
SOURCE: Centers for Disease Control and Prevention. Health Information for International Travel 2005–2006. Atlanta: US Department of Health and Human Services, Public Health Service, 2005.
Mandell, G. L., J. E. Bennett, and R. Dolin. Principles and Practice of Infectious Diseases. 6th ed. Philadelphia: Elsevier, 2004.
Jansen, A., et al. “Leptospirosis in Germany, 1962–2003.” Emerging Infectious Diseases 11 (2005): 1048–1054.
Directors of Health Promotion and Education. “Leptospirosis.” <http://www.dhpe.org/infect/Lepto.html> (accessed March 1, 2007).
Centers for Disease Control and Prevention. “Leptospirosis.” October 12, 2005. <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/leptospirosis_g.htm> (accessed March 1, 2007).