Title : Epidemiological aspects of rabies in an Amazon-Cerrado transition region of northeastern Brazil
Abstract:
Rabies is an acute viral disease that affects mammals, caused by an RNA virus belonging to the family Rhabdoviridae and the genus Lyssavirus. The disease is transmitted through bites or scratches from an infected animal. Rabies was one of the first infectious diseases to be scientifically studied, with a detailed description of symptoms and clinical course. The global incidence of rabies varies among different regions, and it is estimated that it causes around 60,000 deaths worldwide each year, with a higher prevalence where there are no effective control measures. Most cases occur in developing countries where animal vaccination and proper post-exposure prophylaxis are less accessible. The rabies virus has several variants that are specific to each animal reservoir, and in Brazil, five of these variants have already been identified. This study aimed to better understand the epidemiological aspects of the rabies virus variants circulating in the Amazon-Cerrado transition region through immunological and molecular assays, as well as their reservoirs and distribution in the biomes. To achieve this, 62 biological samples sent to reference laboratories in the state of Maranhão between 2015 and 2022 were analyzed using the fluorescent antibody test (FAT) and reverse transcriptase polymerase chain reaction (RT-PCR) techniques. Primers 504 (sense) and 304 (reverse) were used for the N gene in the RT-PCR reactions, amplifying 240 bp, and the positive samples were submitted to Sanger sequencing to identify the antigenic variant. Of all the samples, 74% tested positive in FAT and 63% tested positive in RT-PCR. Among FAT-negative samples, 19% were detectable for the rabies virus by the RT-PCR. Of all samples that tested positive in both tests, only 28% were successfully sequenced, revealing antigenic variants of Desmodus rotundus and Cerdocyon thous. It was observed that these variants circulate in both the Amazon and Cerrado biomes, with the bat variant being more prevalent in the Amazon biome with human cases of rabies in the early 21st century, while the wild canid variant was more prevalent in the Cerrado, as there are reports of this variant in domestic dogs and humans in this Amazon-Cerrado transition region northeastern Brazil. Thus, these results guide epidemiological surveillance procedures that can be used in each specific case with a one health approach.
