Phylogeographic analysis of rabies virus from domestic herbivores and vampire bats in the Rio de Janeiro State, Brazil, between the years 2001 and 2006

Abstract

Rabies is an enzootic disease in Brazil, including Rio de Janeiro state, especially rabies transmitted by vampire bats. All years are accounted large losses of livestock due to this disease in the State. The aim of this study was perform a phylogeographic analysis of rabies virus in the Rio de Janeiro state. It was analyzed a dataset of 58 genetic sequences from the coding region of the N gene. We isolated 35 samples in the Rio de Janeiro between 2001 and 2006 from vampire bats and domestic herbivores in 18 cities of the State. It was retrieved from GenBank 15 and 8 sequences from São Paulo and Minas Gerais states, respectively. With the Beast v1.6 software package, the group of sequences was analyzed by Bayesian Markov chain Monte Carlo method with the nucleotide substitution model K3Puf + G, strict molecular clock and an exponential growth tree prior. The reconstruction of the spatial-temporal dispersion of the samples, with viewing on Google Earth software, was performed by continuous phylogeographic analysis using relaxed random walks (RRW). The tree topology showed at least four main clusters of rabies virus in the Rio de Janeiro state. In a region of the state can exist, concomitantly, more than one virus lineage. In the South region circulate two lineages, three in the Centre, two in the Metropolitan and only one in the Northern region of the Rio de Janeiro state. It can be noticed among the main clusters the formation of sub-clusters, which consist of samples of nearby cities. Only a single sample from Itaboraí (metropolitan region) is included in a cluster with samples from the south of state. The space-time analysis showed the rapid movement of this sample, leaving the South toward the metropolitan region. Probably, this bovine was transported during the incubation period of the disease. In the Rio de Janeiro city was isolated a sample that has no close relationship with any other sequence analyzed. Probably the horse also was introduced in the Rio de Janeiro state during the incubation period of the disease. The movement of the virus among the States showed a spread of the virus from the Rio de Janeiro state towards the Minas Gerais and São Paulo states. In this case, the samples were genetically closer to those of municipalities near the border between the States. The results show an intense movement of rabies across the Rio de Janeiro state. These data can assist in disease control measures in the State.