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Leptospirosis


Leptospirosis is a bacterial zoonosis disease that affects humans and animals. It is caused by bacteria of the genus Leptospira.


Alternative Names

Weil disease; Icterohemorrhagic fever; Swineherd's disease; Rice-field fever; Cane-cutter fever; Swamp fever; Mud fever; Hemorrhagic jaundice; Stuttgart disease; Canicola fever.


Symptoms

High fever, severe headache, chills, muscle aches, and vomiting, and may include jaundice (yellow skin and eyes), red eyes, abdominal pain, diarrhea, or a rash. If the disease is not treated, the patient could develop kidney damage, meningitis (inflammation of the membrane around the brain and spinal cord), liver failure, and respiratory distress.


Many of these symptoms can be mistaken for other diseases. Leptospirosis is confirmed by laboratory testing of a blood or urine sample.


Causes

Leptospirosis are usually caused by exposure to water contaminated with the urine of infected animals.

Clinically, Leptospirosis is caused by various species of Leptospira, a spirochete in the family Leptospiraceae, order Spirochaetales. Leptospira organisms have been found in cattle, pigs, horses, dogs, rodents, and wild animals. Humans become infected through contact with water, food, or soil containing urine from these 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.

Many different kinds of animals carry the bacterium; they may become sick but sometimes have no symptoms. Mostly occurs in warmer climates. The disease is not known to be spread from person to person.


How long is it between the time of exposure and when people become sick?

The time between a person's exposure to a contaminated source and becoming sick is 2 days to 4 weeks. Illness usually begins abruptly with fever and other symptoms. Leptospirosis may occur in two phases. The first phase, called the acute or septicemic phase; after the first phase, with nonspecific signs including fever, chills, headache, muscle aches, vomiting, or diarrhea, the patient may recover for a time but become ill again. If a second phase occurs, it is more severe; the person may have kidney or liver failure or meningitis. This phase is also called Weil's disease.


The illness lasts from a few days to 3 weeks or longer. Without treatment, recovery may take several months.


Risk for Travelers

Travelers participating in recreational water activities, such as whitewater rafting, adventure racing, or kayaking may be at increased risk for the disease, particularly following periods of heavy rainfall or flooding and even in areas not previously considered endemic.


Recent outbreaks of leptospirosis in the US have occurred in Illinois and Florida (CDC, unpublished data), while leptospirosis is endemic to Hawaii. Outbreaks in which US residents acquired leptospirosis have also occurred recently in Malaysian Borneo and Costa Rica.


Clinical pathology

In most cases of leptospirosis there is thrombocytopenia, leukocytosis and neutrophilia with a left shift. The BUN and creatinine are increased due to the renal failure. Electrolyte levels vary according to the degree of renal failure. There may be increase in ALT, AST, ALP and bilirubin due to liver damage. Urine analysis may reveal increased protein and bilirubin.


Ecology

Leptospira is a unique pathogen because of its ability to grow at temperatures as low as 11-13oC, though the optimum growth temperature is still between 28oC and 30oC. Leptospira grows best at pH levels between 7.2 and 7.6, preferring an alkaline habitat to acidic. Leptospirosis, caused by Leptospira, is found most frequently in tropical or temperate climates.




The FA and MC tests can identify specific serotypes. It is also possible to use dark-field microscopy to identify the organism in fluids. This technique requires large numbers of organisms in a very fresh sample to show a positive result.


Disinfection

Leptospira species can be inactivated by 1% sodium hypochlorite, 70% ethanol, glutaraldehyde, formaldehyde, detergents and acid. This organism is sensitive to moist heat (121o C for a minimum of 15 min) and is also killed by pasteurization.


Incubation Period

The incubation period in humans is usually 7 to 12 days, with a range of 2 to 29 days.


Diagnosis

The standard serologic method of diagnosis is a microagglutinationtest. A positive diagnosis is made by finding a four-fold increase in titer in serial serum tests taken at two-four week intervals. The first sample should be drawn before any antimicrobial therapy is begun. There are also fluorescent antibody and immunohistochemical tests to identify the organism in tissue.


Exams and Tests

Diagnosis is most frequently done by testing the blood for antibodies to the bacteria.

Other tests may be done:
  • A white blood cell count generally shows less than 10,000 white blood cells.
  • Urinalysis is usually abnormal.
  • Higher-than-normal creatine kinase is found in approximately 50% of patients.
  • About 40% of patients have a slight to moderate increase in liver enzymes.

How is leptospirosis treated?

Leptospirosis is treated with antibiotics, such as Penicillins, tetracyclines, chloramphenicol, and erythromycin, which should be given early in the course of the disease. Intravenous antibiotics may be required for persons with more severe symptoms. Supportive care needs to be given in complicated cases.


Prevention

The control of infections in livestock and pets reduces the risk of human disease, but the existence of wildlife reservoirs complicates prevention. Rodent control can be important in preventing human infections, particularly in urban areas.

Avoidance of contact with contaminated or potentially contaminated bodies of water especially in tropical climates can decrease the risk of infection.


Domestic animals should not be allowed to urinate in water that humans contact. Draining wet areas may also decrease the incidence of disease. Food should also be protected from sources of infection. Personal hygiene and protective clothing are important preventative measures in high risk occupations.


Gloves and face shields can help prevent infections when working with infected animals or tissues. Rubber boots can decrease the risk of infection in sewer workers and agricultural workers who may wade in urine-contaminated water. Human vaccines are available for workers in high risk professions in some countries but are not used in the U.S. Immunization is relatively serovar specific, and protects only against the serovar(s) in the vaccine or closely related serovars. Yearly vaccination is required and side effects, including painful swelling, can be seen.

If you are exposed to a high risk area, taking doxycycline may decrease your risk of developing disease.







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