Outbreaks of Attacks by Hematophagous Bats in Isolated Riverine Communities in the Brazilian Amazon: A Challenge to Rabies Control

Abstract

Human rabies has re-emerged in Latin America due to bat associated transmission. We present data related to attacks by hematophagous bats in three riverine communities in the Rio Negro basin, Brazilian Amazon. A cross-sectional survey was carried out to obtain demographic and epidemiological data through interviews with 201 inhabitants. A total of 721 bat attacks with bites took place from 2004 to 2006, 238 (33%) reported by residents in Campinas do Rio Preto, 329 (46%) in Águas Vivas and 154 (21%) in the community of Malalahá. Incidence density among surveyed inhabitants was 84 attacks/100 persons-years in Campinas do Rio Preto, 249 attacks/100 persons-years in Águas Vivas and 81 attacks/100 persons-years in Malalahá. The proportion of surveyed inhabitants bled by bats at least once was 67% (63/94) in Campinas do Rio Preto, 96% (42/44) in Águas Vivas and 62% (39/63) in Malalahá. Among subjects bled by bats, the average number of bites was 4.6 ± 4.2 standard deviations (SD) in Campinas do Rio Preto, 8 ± 6 SD in Águas Vivas and 4.1 ± 3.9 SD in Malalahá. Regarding houses, 67% (26/39) had animals in the peridomestic environment (chickens and/or dogs) and all were vulnerable to bats due to gaps in the walls and/or in the windows and doors. In 13 dwellings, rudimentary protection against bats through the fixation of fishing nets and/or straw nets to the windows and other openings was observed. Among dwellers reporting attacks, 48% (68/144) received the full post-exposure anti-rabies vaccination protocol with five doses of diploid human cell vaccine, 28% (39/144) received an incomplete schedule (1-4 doses), and 26% (37/144) did not receive any dose. No cases of rabies were reported during the study; however, regular pre-exposure vaccination in the studied populations must be considered.