Is oral penicillin an effective chemoprophylaxis against leptospirosis? A placebo controlled field study in the Kandy District, Sri Lanka.

Leptospirosis poses a severe threat to the lives of farmers in Sri Lanka, thus, development of an effective chemoprophylaxis is deemed essential. We tested oral penicillin as chemoprophylaxis against leptospirosis in high transmission areas in central Sri Lanka in October 2005. Eight hundred active farmers were randomly assigned to take either oral penicillin (500 mg bid) or a similar looking placebo over a month during active farming season. The primary study point was the incidence of serologically confirmed leptospirosis. Data were available for 602 subjects of whom 319 (152 taking penicillin and 167 taking placebo) had good compliance, shown by tablet count. Of 5 subjects hospitalized with fever, 3 had serological evidence of leptospirosis, all of whom belonged to the placebo group. Therefore, oral penicillin may be effective chemoprophylaxis against leptospirosis.