Leptospirosis

• Leptospirosis is an infectious disease that can occur in humans and animals worldwide.
• A type of spiral-shaped bacterium called a spirochete, Leptospira interrogans, causes leptospirosis.
• High risk factors for leptospirosis include close association with animals and the water and soil they may contaminate with infected urine.
• Symptoms and signs of leptospirosis are highly variable and range from no symptoms to nonspecific symptoms including
  • high fever,
  • chills,
  • headache, and
  • abdominal symptoms to Weil's disease with organ dysfunction.
• Diagnosis of leptospirosis is done by isolating the bacteria from the patient. Blood tests are also available.
• There are antibiotics that are effective in treating leptospirosis.
• Most people infected with Leptospira interrogans bacteria have a good prognosis; a few have a more guarded prognosis.
• Vaccines are available for humans and animals in some countries. There is no vaccine available commercially for humans in the U.S. Available vaccines are limited because they usually only protect well against a single serovar. Doxycycline (Vibramycin, Oracea, Adoxa, Atridox) has been used as a short-term preventive treatment to protect some humans from leptospirosis.

Leptospirosis (also known as Weil's disease, grippotyphosa, and canicola) is a disease caused by bacteria (Leptospira interrogans) that produce a wide range of symptoms that may occur in two phases; some patients may develop kidney or liver failure, respiratory failure, meningitis, or even death. The bacterial infection is spread by the urine of infected animals from many species, both domesticated (such as dogs and horses) and wild infected animals (such as rodents or wild pigs). It is termed a zoonotic disease or a zoonosis because it occurs in wild animals. The bacteria can survive in freshwater and soil for months. The disease is most common in temperate and tropical climates. The infecting bacteria occur worldwide (for example, in the United States, Leptospira has been found in Hawaii's freshwater ponds and waterfalls).

The cause of leptospirosis is bacteria (genus Leptospira and species interrogans), a Gram-negative spirochete (spiral-shaped bacteria). The Leptospira bacteria infect many types of animals (many wild animals, rodents, dogs, cats, pigs, horses, cattle, for example) that subsequently contaminate water, lakes, rivers, soil, and crops when they urinate because the bacteria are present in urine. The bacteria then infect humans when they invade through breaks in the skin or mucus membranes or when people ingest them. The bacteria multiply in the liver, kidneys, and central nervous system. Person-to-person transfer of this disease is rare.

In general, human leptospirosis is considered weakly contagious. This is because, like other animals, humans can shed leptospirosis in the urine during and after illness. Consequently, individuals exposed to the urine of humans who are infected may become infected. For example, although the bacteria are not airborne and have a low risk of being in saliva, individuals handling wet bedding or blood-soaked material from an infected person can increase the chances of getting the infection. There are a few reports of transmission between sexual partners, but the incidence of this type of spread seems very low. Unfortunately, pregnant mothers who get leptospirosis can infect their fetus.

The contagious period for leptospirosis depends on how long viable organisms are shed in the urine. Most individuals will shed organisms in the urine for a few weeks but there are reports that humans can continue to shed the organisms in urine for as long as 11 months. Some experts suggest that there is risk for up to 12 months after getting the initial infection.

The incubation period for leptospirosis is approximately seven to 12 days but it may range from two to 30 days.

Risk factors include occupational exposure in people to with farm animals, wild animals, and to contaminated water and soil (farmers, slaughterhouse workers, veterinarians, miners, military personnel, disaster workers and victims, for example). People who participate in outdoor activities such as camping or kayaking are also at higher risk for infection. Any exposure to sewage or animal waste, including stools from infected dogs, increases the risk of getting leptospirosis. Heavy rainfall may cause the bacterial infection to increase in a population that experiences flooding. This is evidenced by a reported four deaths from leptospirosis due to flooding in Puerto Rico.

The symptoms and signs of leptospirosis are variable and are similar to those seen in many other diseases (dengue fever, hantavirus, brucellosis, malaria, and others). Symptoms can arise about two days to four weeks after exposure to the bacteria. Although some people have no symptoms, others may exhibit

• high fever,
• chills,
• headache,
• muscle aches and muscle pain,
• fatigue,
• sore throat,
• abdominal pain,
• vomiting,
• diarrhea,
• jaundice,
• pain in the joints or muscles,
• rash, and
• reddish eyes.

These symptoms usually occur in the first phase of the infection, and when present, they often occur abruptly. Some patients resolve their symptoms and do not progress to the second phase. Others may seem to briefly recover but relapse (about 5%-10%) with more severe symptoms and organ damage in the severe form of the disease. The second-phase symptoms may overlap with the first-phase symptoms in severe disease and include the following:

• Jaundice
• Renal failure (kidney damage)
• Pulmonary hemorrhage
• Cardiac arrhythmias
• Pneumonitis
• Septic shock

This is the second phase of leptospirosis, called Weil's disease. If it's not treated, it may not resolve for several months, and some patients may develop long-term complications such as kidney and lung problems. The death rate is about 1%-5%.

Clinic doctors, primary care doctors, pediatricians, and emergency-medicine specialists often treat leptospirosis in countries where it is endemic and the patients are in the first phase of the disease. Other specialists are often consulted if the patient begins to enter the second phase of the disease. These specialists may include critical care, infectious-disease, hospitalists, internists, pulmonologists, cardiologists, and kidney specialists.

Physicians make a presumptive diagnosis based on the patient's history and physical exam. Only specialized labs perform serological serology tests for leptospirosis serogroups (specific types of the bacteria that react with certain antibodies). Health care professionals may perform definitive tests by isolating the bacteria from the patient (blood or CSF) or by a positive microscopic agglutination test (MAT). Other tests (ELISA, PCR, urine dipsticks) may provide additional evidence of infection. Patients with severe symptoms should be treated as confirmatory tests are time consuming.

Although there is controversy about using antibiotics in the first phase of leptospirosis, antibiotics (penicillin - penicillin G, ampicillin [Omnipen, Polycillin, Principen], amoxicillin [Amoxil, Trimox, Moxatag, Larotid], or erythromycin [E-Mycin, Eryc, Ery-Tab, PCE, Pediazole, Ilosone]) are recommended for treatment of patients with phase two or more severe symptoms. Some patients may require IV antibiotics and supportive hospital care such as rehydration.

For those clinicians who choose to treat phase-one patients, the choice of antibiotics includes the above, but many choose to treat with doxycycline.

Overall, the prognosis of leptospirosis is good. Many people become infected and spontaneously recover without treatment. However, the prognosis worsens as the symptoms increase. People with Weil's disease may have a prognosis ranging from good to poor, depending on their response to treatment. Pregnant women who become infected have a high rate of fetal mortality, especially if they acquire the disease early in pregnancy.

A leptospirosis vaccine is not currently available in the U.S.; however, high-risk workers in some European and Asian countries may have access to a vaccine. Unfortunately, the vaccines are serovar-specific (bacterial-strain specific) and thus do not offer widespread protection as there are over 200 serovars (immunologically distinct types of the bacteria). Some vaccines are available for animals but these, like the human vaccines, are only effective against a narrow range of serovars. In addition, side effects of the vaccine can cause painful swelling. Chemoprophylaxis (using drugs to prevent illness) is possible under certain circumstances. Some individuals who may have high short-time risk (for example, military personnel) may take doxycycline (200 mg/week), beginning one to two days before potential exposure to have about a 95% chance of preventing infection with chemoprophylaxis. This preventive treatment is not recommended for long terms of exposure.

Avoiding contact with animal excrement, good hygiene, and avoiding contaminated water and soil are other ways to reduce the chance of getting leptospirosis.

Dogs, and many other animals, can be infected with leptospirosis. Veterinarians have access to vaccines that can protect (or prevent) leptospirosis in dogs and other animals for at least 12 months. This vaccination may help protect the animals' owners and other local or family owned animals from the disease for approximately one year.