Leptospirosis, also known as Weil's disease, icterohemorrhagic fever (2), swamp fever, cane fever, and Fort Bragg fever (1), is caused by spirochetes of the genus Leptospira (6). The etiologic agent is Leptospira interrogans (8); this bacteria is corkscrew-shaped and is spread by contaminated urine from animals. Leptospira have the means of motility by axial filaments, which provide the bacteria with an accessible quality to penetrate the human skin and enter the bloodstream (1).
Leptospirosis is carried by a number of different reservoirs, including animals, soil, and water (6). The main transfer of this infectious disease occurs when there is contact with infected animal urine; these animals include pigs, rats, cattle, and dogs (6). The disease is transferred both directly and indirectly. The bacteria invades the human host by entering via the nose, mouth, eyes, and cuts in the epidermis (3). Direct measures of entrance are made when there is contact with urine or tissues of infected animals (5). Indirect contact is made through the exposure of infected ponds, streams, and puddles (11), surviving in freshwater for up to four weeks (1). Also, contact is made indirectly through exposure to contaminated soil or vegetation, inhalation of droplet- aerosols of infected fluids, and ingestion of contaminated foods (5).
Once the bacteria has entered into the body, there is an incubation period of about two to twenty-five days before detection of signs and symptoms can be observed (17). Ninety percent of cases are considered anicteric and occur in two phases, the septic phase and the immune phase. It can be identified in the testing of blood, CSF, and tissues, using etiological tests, such as the darkfield examination. Also, detection is made using serological testing, including microscopic agglutination (searching for fourfold rise in titer), macroscopic slide agglutination, and the ELISA test (presence of IgM bodies) (8). The septic phase includes the blood, CSF, and tissues; symptoms range from a mild flu-like illness (13), headache, chills, acute abdominal pain, red eyes, depression, loss of memory, and myalgia (6). The immune phase (leptospirosis remains in urine and aqueous humor) includes more severe conditions including rash (8), jaundice, renal insufficiency, meningitis, and possibly death (7). Symptoms last from a few days to several weeks (11).
Leptospirosis is controlled in a number of ways, including oral doxycycline and amoxicillin (in mild cases), as well as the use of ampicillin and intravenous penicillin (in serious cases). A human vaccine against the disease has not yet been discovered, but is under scientific study (1). Prevention of the disease includes controlling of rodents (8), segregating of infected domestic animals (6), educating the public on modes of transmission with contaminated waters, and protection of workers in hazardous conditions with boots and gloves (5). Those considered high risk for contracting the disease are workers in rice fields, sugar cane plantations, mines, sewer systems, and slaughterhouses; as well as animal caretakers and veterinarians (4).
The incidence of Leptospirosis in the United States is 100-200 cases reported annually (4). The first case was reported in 1907, occurring in Louisiana. Leptospirosis has fluctuated in the number of cases in the United States between 1985 to 1994; in 1985, there were fifty seven reports, 1990 showed seventy-seven reports, and 1994 has declined to about thirty-eight incidences (10). Hawaii is known to harbor fifty percent of cases occurring annually in the United States (4), especially during the summer months when Leptospirosis is most likely to become a risk (12). The northeastern coast has reported an increase in contracting the Leptospirosis disease, especially in New York where there has been an outbreak of 200 cases in the last eighteen months (9). In 1998, 74 of 369 triathlon participants were infected with the disease in Illinois after prolonged swimming in a lake (7).
The incidence figures relating to the rest of human population, those based globally, have been recognized to be increasing. There have been reports of thirty-seven cases in Ecuador, including ten deaths (16). There are about eighty cases a year in Wales and England (13). In Singapore, there have been four related deaths in the last five years since 1997, and just in the past eighteen months there have already been fourteen cases and is noted to be rising(14). Queensland, Australia has reported incidence figures on a rise, as well; in the first three months of this year (1999), there have been ninety-nine cases, compared to the twenty-two reported in 1998 (15). In 1995, Nicaragua calculated thirteen deaths and more than 2,000 ill. In 1996, Costa Rico reported nine of twenty-six people ill after exposure to contaminated rivers (7). Also, the actress Jane Seymour became infected with the disease in 1997 while filming a movie in Costa Rico (1).
Leptospirosis has taken its toll on many human lives, thankfully being of limited risk in the United States. It is a zoonosis due to the fact that humans are the incidental host of infected animals (1). More than 250 serotypes have been discovered, making the disease difficult to cure with a particular antibiotic (7). Though scientists have come a long way with the identification of Leptospirosis, there is still much to be remedied, especially the eventual cure with a vaccine. The risk of becoming infected with the disease is a frightening possibility due to the fact that there are so many different strains of the bacteria. Leptospirosis is of world-wide distribution (8), continuing to be of threat to those infected with it.
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