Use of doxycycline for leptospirosis after high-risk exposure in São Paulo, Brazil

Abstract

A clinical trial pilot study, double-blinded, randomized, and controlled with a placebo to assess the effectiveness of oral doxycycline (200 mg, single dose) in preventing leptospirosis after high exposure to potentially contamined water was performed in São Paulo, SP, Brazil. Confirmed cases were defined as those with leptospira IgM antibody and symptoms; asymptomatic cases were those presenting with IgM antibodies but no symptoms; and suspected cases were individuals with symptoms but no IgM antibody. Forty subjects were given doxycycline and 42 were given placebo. In the drug-treated group there were 2 confirmed cases, 11 asymptomatic cases, and 6 suspected cases. In the placebo group there were 5 confirmed, 6 symptomatic, and 5 suspected cases. Even though we found a protective association of doxycycline for confirmed leptospirosis cases (RR = 2.3) and seroconversion only (RR = 2.0), the association was not statistically significant because of the small number of individuals enrolled in this pilot study. We observed that the 22% of the volunteers already had IgM antibodies to leptospirosis at the first sampling. Finally, the attack rate to confirmed, asymptomatic, and suspected cases of Leptospirosis was 8.5%, 22%, and 13%, respectively, in this population.

Translated abstract

Um ensaio clínico, duplo-cego, ao acaso, e controlado com placebo para aferir a eficácia da doxiciclina (200 mg, dose única) em prevenir leptospirose após exposição de alto risco com água potencialmente contaminada foi realizado em São Paulo, SP, Brasil. Casos confirmados foram definidos como aqueles que apresentavam anticorpos IgM anti-Leptospira e sintomas; casos assintomáticos eram aqueles que apresentavam somente anticorpo IgM, casos suspeitos apresentavam sintomas, porém sem anticorpo IgM. 40 indivíduos tomaram doxaciclina e 42 tomaram placebo. No grupo tratado houve 2 casos confirmados, 11 assintomáticos e 6 casos suspeitos. No grupo placebo houve 5 casos confirmados, 6 assintomáticos e 5 casos suspeitos. Apesar de haver uma associação protetora da doxaciclina nos casos confirmados (RR = 2,3) e soroconversão (RR = 2,0), a associação não foi estatisticamente significante devido ao pequeno número de indivíduos envolvidos no estudo. Foi observado que a taxa de ataque de casos confirmados, casos assintomáticos e casos suspeitos de leptospirose foi 8,5%, 22%, e 13%, nessa população.