The challenge posed by leptospirosis

Clinical management

Leptospirosis may be the world's most widespread zoonosis.3 Although it is endemic in tropical countries such as Brazil, sporadic outbreaks are not uncommon in temperate regions such as the United States.4 Typically, humans are infected through occupational or recreational exposure to water, soil or vegetation contaminated by the urine of infected animals; common reservoirs include swine, cattle, dogs, raccoons and rats. Leptospires enter the body through cut or abraded skin, mucous membranes and conjunctivae and cause vasculitis.

The incubation period ranges from 4 days to 4 weeks. The symptom spectrum is broad. The illness usually begins abruptly with fever, chills, rigours (particularly in the calves and lumbar region) and headaches, and may include conjunctivitis, abdominal pain, vomiting, diarrhea and meningeal signs. The acute septicemia may be followed by a secondary phase of severe disease characterized by jaundice, renal failure, hemorrhage or hemodynamic collapse.4

The organism may be isolated from samples of blood and cerebrospinal fluid obtained during the first 10 days of illness, and in the urine following the first week of illness. The microagglutination test is the standard for serological diagnosis,5 but it can be time consuming and difficult to perform. Physicians who suspect a case of leptospirosis should contact their local medical officer of health or the Population and Public Health Branch (formerly the Laboratory Centre for Disease Control) at Health Canada for advice on sample collection and laboratory confirmation.

The CDC recommends that patients with mild cases be treated with doxycycline (100 mg orally, twice daily for 7 days) and that those admitted to hospital because of persistent fever, hepatic or renal failure or severe neurologic disturbance be treated intravenously with penicillin G (1.5 million units every 6 hours for 7 days).1 However, a recent Cochrane review of the randomized controlled trials in which antibiotics were used to treat leptospirosis6 identified only 3 trials that met inclusion criteria, 2 of which were of questionable quality. The authors of the review concluded that there is insufficient evidence to provide clear guidelines for antibiotic regimens for treating leptospirosis, although the evidence suggests that penicillin “may cause more good than harm.”

Prevention

Chemoprophylaxis for leptospirosis is 200 mg of doxycycline orally once per week.7 The merits of one 200-mg dose of doxycycline orally for postexposure prophylaxis are unknown. Steps to prevent leptospirosis include recognizing and avoiding swimming or wading in contaminated water and wearing protective clothing and gear such as boots, gloves and aprons. Other steps include controlling rodents, immunizing farm animals and pets, and segregating infected domestic animals. For further information see references 8 and 9. —