A cross-sectional survey conducted among evening students was used to determine
the prevalence of Wuchereria bancrofti infection in Maceió, capital of the
State of Alagoas, northeast Brazil. A single thick-blood smear was used, being collected
between 10 p.m. and 12 a.m. From a total of 29,551 students enrolled at evening
elementary schools in the 33 city sectors, 16,569 (56.4%) were random selected for inclusion in the
study. From those, 10,857 (65.5%) were interviewed and examined and 73 (0.7%) were found to
have microfilaraemia. Autochthonous W. bancrofti carriers live in 10 of the 33 city
sectors, suggesting a focal distribution. Moreover, 84% of infections were diagnosed
among 29% of all students examined, inhabiting three contiguous sectors at the city central area,
presenting infection rates up to 5.3%. Students living in city sectors with prevalence of
microfilariae carriers greater than 1% were found to have a higher risk for infection when
compared to students from the rest of the town [Relative Odds (RO) 12.8, 95% CI 6.7 -
25.1]. Eleven positive individuals from non endemic areas were living in Maceió for
more than 10 years; time of residence in the area was a major risk factor for infection
among students not born in the region (p<0.01). Regarding sex, male students presented a higher
proportion of positive (RO 1.7, 95% CI 1.1 - 2.9).
