Leptospirosis is a potential zoonosis with protean manifestations, caused by pathogenic spirochetes of the genus Leptospira. The organism infects a variety of wild and domestic mammals, especially rodents, cattle, swine, dogs, horses, sheep and goats.

Animals can be asymptomatic or develop clinical infection, which can be fatal. Reservoir animals shed the organism in their urine intermittently or continuously throughout life, resulting in contamination of water.

Routes of infection

1. Humans gets infected after exposure to animal urine, contaminated water or soil, or infected animal tissue through cuts or abraded skin, mucous membranes, or conjunctiva. Controversy exists as to whether Leptospira can penetrate the intact skin.
2. The infection may rarely be acquired by ingestion of food contaminated with urine or via aerosols.
3. Large outbreaks are associated with increased rainfall or flooding, which presumably increased the risk of exposure to contaminated water

Risk factors are occupations like farmers, pet traders, military personnel, laboratory workers; recreational activities like freshwater swimming, canoeing, kayaking, trail biking; household exposure with pet dogs, domesticated livestock, rainwater catchment systems, infestation by infected rodents and walking barefoot through surface water or skin lesions contact with wild rodents.

Clinical presentation

1. The clinical course is variable. The disease may manifest as a subclinical illness followed by seroconversion or a severe, potentially fatal illness with multiorgan failure.
2. Clinically, it presents with the abrupt onset of fever, rigors, myalgias, and headache in most patients. Conjunctival suffusion in a patient with a nonspecific febrile illness should raise suspicion.
3. Most cases are mild to moderate. However, the course may be complicated by renal failure, uveitis, hemorrhage, acute respiratory distress syndrome with pulmonary hemorrhage, myocarditis, and rhabdomyolysis.
4. A high index of suspicion is required to make the diagnosis as lab findings are nonspecific. The microscopic agglutination test is a reference standard assay
5. In the absence of a definitive laboratory diagnosis, administration of empiric treatment is appropriate.
6. All over India doctors seeing travellers returning from vacations involving recreational activities associated with potential environmental Leptospira exposure in high-risk regions should consider the possibility of leptospirosis.

Treatment

1. Antibiotics shorten the duration of illness and reduce shedding of the organism in the urine.
2. Treatment of choice in mild leptospirosis is oral doxycycline or azithromycin. Both agents are also effective for rickettsial disease, which can be difficult to distinguish from leptospirosis. Doxycycline should be avoided in children <8 years of age unless no other treatment options are available and in pregnant women; reasonable alternatives include azithromycin or amoxicillin.
3. In severe leptospirosis the antibiotics are parenteral penicillin, doxycycline and third-generation cephalosporins. Penicillin and cephalosporins lack activity against rickettsiae.

Prevention

1. There is no human vaccine widely available.
2. Prevention include avoiding potential sources of infection, administration of doxycycline prophylaxis for individuals at high risk of exposure, and animal vaccination.