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. 2012 Jan 16;5:32. doi: 10.1186/1756-0500-5-32

Molecular epidemiology of livestock rabies viruses isolated in the northeastern Brazilian states of Paraíba and Pernambuco from 2003 - 2009

Nobuyuki Mochizuki 1, Hiroyuki Kawasaki 1, Maria LCR Silva 2, José AB Afonso 3, Takuya Itou 1,, Fumio H Ito 4, Takeo Sakai 1
PMCID: PMC3285087  PMID: 22243739

Abstract

Background

Limited or no epidemiological information has been reported for rabies viruses (RABVs) isolated from livestock in the northeastern Brazilian states of Paraíba (PB) and Pernambuco (PE). The aim of this study was to clarify the molecular epidemiology of RABVs circulating in livestock, especially cattle, in these areas between 2003 and 2009.

Findings

Phylogenetic analysis based on 890 nt of the nucleoprotein (N) gene revealed that the 52 livestock-derived RABV isolates characterized here belonged to a single lineage. These isolates clustered with a vampire bat-related RABV lineage previously identified in other states in Brazil; within PB and PE, this lineage was divided between the previously characterized main lineage and a novel sub-lineage.

Conclusions

The occurrences of livestock rabies in PB and PE originated from vampire bat RABVs, and the causative RABV lineage has been circulating in this area of northeastern Brazil for at least 7 years. This distribution pattern may correlate to that of a vampire bat population isolated by geographic barriers.

Background

Rabies is a fatal infectious disease that causes encephalomyelitis. In Brazil, various rabies viruses (RABVs) have been isolated from numerous animal species, including dogs, foxes, cats, and cattle, as well as from hematophagous, insectivorous, and frugivorous bats. Vampire bats, particularly Desmodus rotundus, are an important rabies vector in Latin America. Transmission from vampire bats to humans has been reported, primarily in the Amazon regions of Brazil and Peru, and a large number of cases of cattle rabies transmitted by vampire bats also have been reported in Brazil [1]. Since the introduction of a regional elimination program, the incidence of human and canine rabies in Latin America has fallen by 90% over the past 20 years. However, northeastern Brazil remains a "hotspot" for human rabies because of circulation of the virus among the dog population [2]. Carnieli Jr. et al. reported the molecular characterization and epidemiology of RABVs isolated from canids in northeastern Brazil [3-5], and Shoji et al. reported the genetic and phylogenetic characterization of RABVs isolated from wild fox, insectivorous bats, and livestock in Paraíba (PB) [6]. In Olinda, a city in Pernambuco (PE), 7,062 patients underwent prophylactic antirabies treatment between 2002 and 2006 [7]. Molecular and geographic analyses of livestock rabies in central and southeast Brazil revealed that RABVs isolated from livestock were related to the virus found in vampire bat populations, and this epidemiological pattern was maintained over time and space in these areas [8-11]. However, little or no information on the molecular epidemiology of RABVs has been reported for the virus isolated from livestock in PB and PE. The aim of the present study was to analyse the molecular epidemiology of RABVs circulating among livestock, especially cattle, in these areas between 2003 and 2009.

Results

The sequences of 890 nt PCR products, corresponding to nucleotides 89-978 of the Pasteur vaccine (PV) strain, were determined for all 52 RABV isolates. Among the 52 isolates, the nucleotide and amino acid sequence identities were 97.7-100% and 97.9-100%, respectively.

Phylogenetic analysis based on the sequences of 890 nt of the N gene revealed that the 52 RABV isolates included in this study clustered with a vampire bat-related RABV lineage; these isolates did not cluster with the dog-, fox-, or insectivorous bat-related RABVs (Figure 1). Comparison with RABVs isolated from other states in Brazil indicated that these 52 RABV isolates belonged to a single lineage; furthermore, this lineage was divided between a previously characterized main lineage (B) and a novel sub-lineage (A) consisting of several isolates located in PE. Geographical plotting showed that RABV isolates of the novel sub-lineage were derived from neighbouring areas (Figure 2). The topographical distributions of isolates from lineages A and B could not be distinguished in the areas covered by this study.

Figure 1.

Figure 1

A phylogenetic tree based on the nucleotide sequences of the N gene. A phylogenetic tree based on the nucleotide sequences of 890 nt (bases 89-978) of the N gene was constructed using the method devised by Saitou and Nei [12]; the bootstrap probabilities of each node were calculated using 1,000 replicates. The designations BRbv, BRsp, BRgt, BRhr, BR-Pfx, and BR-DR indicate samples from Brazilian cattle, sheep, goats, horses, foxes, and vampire bats, respectively. MOKV and ABLV denote the Mokola virus and Australian bat lyssavirus, respectively. State abbreviations are as follows: PB, Paraíba; PE, Pernambuco; GO, Goiás; SP, São Paulo; RJ, Rio de Janeiro; MT, Mato Grosso; TO, Tocantins; MA, Maranhão; PA, Pará; MS, Mato Grosso do Sul. The triangle and star symbols represent the new sub-lineage (group A) and the previously reported lineage (group B), respectively.

Figure 2.

Figure 2

Geographic distribution of rabies virus isolates in the Brazilian states of Paraíba and Pernambuco. (a) Map of Brazil indicating location of states pertinent to this study. State abbreviations are as follows: PB, Paraíba; PE Pernambuco; GO, Goiás; SP, São Paulo; RJ, Rio de Janeiro; MT, Mato Grosso; TO, Tocantins; MA, Maranhão; PA, Pará; MS, Mato Grosso do Sul. (b, c) Detailed geographic distribution of livestock isolates classified as genetic variants in the states of PB (b) and PE (c). The two symbols (triangle and star) correspond to the new sub-lineage and previously reported lineage, respectively, as used in Figure 1. Samples for which the geographic origin and the genetic variant are identical are illustrated using the same symbol. Brazilian maps were obtained from Brasil em Relevo - Embrapa Monitoramento por Satélite http://www.relevobr.cnpm.embrapa.br/.

Discussion

Segments of the N gene from the 52 RABV isolates, collected from PB and PE between 2003 and 2009, were sequenced and phylogenetically analysed. This N gene segment displayed greater than 97.7% nucleotide and amino acid sequence identity among these 52 RABVs. This correlation implies that the lineage has been maintained during transmission in PB and PE.

The phylogenetic analysis described here indicates that all of the livestock RABVs in PB and PE were derived from vampire bat rabies. Furthermore, the present study reveals that there are two RABV lineages that are separate from other regional Brazilian vampire bat-related RABV lineages. The first, sub-lineage A, consists of BRbv1173 (collected in PB in 2004) and another seven RABV isolates collected in PE in 2008-2009; the second, sub-lineage B, consists of isolates collected in PB in 2003-2009 and in PE in 2007-2009. Comparison among RABV isolates from multiple northern states of Brazil revealed that lineages from PB and PE were distinct from those obtained from the Maranhão (MA) state. Because of geographical barriers (mountains and rivers) between PB/PE and MA, it would be difficult for vampire bats (the prime vector for RABV) to move freely between PB/PE and MA. Geographical mapping (Figure 2) demonstrates that sub-lineage A was located mainly in high-altitude areas of PE, while sub-lineage B was widely distributed and present in both PE and PB. Thus, these two lineages seem to correlate with geographic factors and/or vampire bat populations, but do not appear to correlate with the year of isolation. Using a 203 nt segment (bases 109 to 311) of the N gene, Kobayashi et al. [8,9] reported the existence of at least 24 RABV genetic variants among vampire bat-transmitted cases of rabies in cattle in Brazil; the distribution of several of these RABV genetic variants was found to be delimited by geographic boundaries, including mountain ranges and rivers. Our analysis (data not shown) using the same 203 nt segment reveals that the 52 RABV isolates (from PB and PE) of the present study correlate with the same PB lineage described by Kobayashi et al. These results indicate that livestock rabies has been transmitted by vampire bats in PB and PE during this study period. Furthermore, this RABV lineage seems to have been circulating in this area for at least 7 years, with transmission affected by geographic factors and resulting in dispersion of vampire bats among regional populations.

Previous reports have shown human exposure to vampire bat-transmitted rabies in northeastern Brazil, including PE [1,7]. The present phylogenetic analysis suggests that rabies epidemics that occurred in cattle in PB and PE were transmitted by vampire bats. These RABV isolates comprised a lineage independent from that of other Brazilian isolates, with the distinction reflecting isolation from neighbouring regions by geographic factors. Thus, the vampire bat-derived rabies in this area represents an endemic disease, suggesting that the regional control of vampire bat rabies in this area may be a workable model for local elimination of human and livestock rabies.

Conclusions

The present study indicates that occurrences of livestock rabies in PB and PE were caused by vampire bat RABVs, and that this RABV lineage has been circulating in this area of northeastern Brazil for at least 7 years. This pattern of distribution may correlate to that of a vampire bat population isolated by geographic barriers.

Methods

The 52 RABV isolates used in this study were obtained from cattle (46), sheep (3), goats (2), and horse (1), and were collected in PB and PE between 2003 and 2009 (Table 1). Brain specimens from these livestock were diagnosed as RABV-positive by an immunofluorescent antibody test and a mouse inoculation test. These study procedures were implemented in accordance with the Institutional Guidelines for Animal Experiments at the Campina Grande University under the permission (number 129/2009) of the Committee for Experimental Animals of this College. Viral RNA was extracted from the brains of livestock using the QIAamp Viral RNA Mini Kit (Qiagen, Hilden, Germany). Nucleoprotein (N) gene sequences from the Brazilian RABV isolates were amplified using RT-PCR with primers JW12 (5'-ATGTAACACCYCTACAATG-3') (position: 55-73 of PV) and N8 (5'-AGTTTCTTCAGCCATCTC-3') (position: 1585-1568 of PV), followed by hemi-nested PCR with primer pairs as follows. Primer pair A consisted of JW12 and P2 (5'-CCCATATAACATCCAACAAAGTG-3') (position: 1029-1007 of PV), and generated a 975-nt amplicon. Primer pair B consisted of P1 (5'-CTACAATGGATGCCGACAAGA-3') (position: 66-86 of PV) and N8, and generated a 1,520 nt amplicon. The nucleotide sequences of RABVs from Brazilian foxes, livestock, and hematophagous and insectivorous bats were obtained from GenBank (Table 1). Cycle sequencing, nucleotide and amino acid sequence alignments, and phylogenetic analyses were performed as previously described [13,14]. The geographic origins of the RABV isolates sequenced from the Brazilian livestock were plotted at the municipal level of the respective federal states using MapInfo Professional GIS software (ver. 8.0, MapInfo Japan K.K., Tokyo, Japan). Brazilian maps were obtained from Brasil em Relevo - Embrapa Monitoramento por Satélite [15].

Table 1.

Brazilian rabies virus isolates used in this study

Sample*1 Species Location State*2 Year Lineage of PB and PE*3 Accession No. Reference
BR-DR6 Desmodus rotundus Laje de Muriae RJ 1998 AB297633 [16]

BR-DR7 Desmodus rotundus Itaperuna RJ 1997 AB297634 [16]

BR-M1(BR-Pbt1) Molossus sp. Patos PB AB206414 [6]

BR-M2(BR-Pbt2) Molossus sp. Patos PB AB206415 [6]

BR-M3(BR-Pbt3) Molossus sp. Patos PB AB206416 [6]

BR-M4(BR-Pbt4) Molossus sp. Patos PB AB206417 [6]

BR-Pfx1 Fox Patos PB 2002 AB362483 [13]

BR-Pfx3 Fox Patos PB 2001 AB206409 [6]

BR-Pfx5 Fox Patos PB 2002 AB206411 [6]

BR-Pfx6 Fox Patos PB 2002 AB207884 [6]

BRbv30 Cattle Morrinhos GO 1999 AB083803 [17]

BRbv32 Cattle Sao Roque SP 1994 AB083805 [17]

BRbv36 Cattle Nova Olinda TO 1998 AB083809 [17]

BRbv39 Cattle Colinas TO 1999 AB083811 [17]

BRbv43 Cattle Alto Taquari MT 1999 AB083813 [17]

BRbv49 Cattle Piraju SP 1989 AB083817 [17]

BRbv50 Cattle Corumbaiba GO 1999 AB083818 [17]

BRbv55 Cattle Montes Altos MA 1998 AB675602*4 [8]

BRbv56 Cattle Iporá GO 1998 AB675603*4 [8]

BRbv76 Cattle Xinguará PA 2002 AB675604*4 [8]

BRbv80 Cattle Ipameri GO 2001 AB675605*4 [8]

BRbv103 Cattle Nova Crixás GO 2001 AB675606*4 [8]

BRbv133 Cattle Xambioa TO 2000 AB675607*4 [8]

BRbv140 Cattle Natividade TO 2000 AB675608*4 [8]

BRbv141 Cattle Nova Crixas GO 2000 AB675609*4 [8]

BRbv183 Cattle Natividade TO 2001 AB675610*4 [8]

BRbv190 Cattle Pocone MT 2002 AB675611*4 [9]

BRbv192 Cattle Nobres MT 2002 AB675612*4 [8]

BRbv215 Cattle Rosario Oeste MT 2002 AB675613*4 [9]

BRbv251(BR-Pbv1) Cattle Patos PB 2003 PB/PE-B AB206423 [6]

BRbv252(BR-Pbv2) Cattle Patos PB 2003 PB/PE-B AB206424 [6]

BRbv254(BR-Pbv3) Cattle Patos PB 2003 PB/PE-B AB206425 [6]

BRbv255(BR-Pbv5) Cattle Patos PB 2003 PB/PE-B AB206426 [6]

BRbv257(BR-Pbv7) Cattle Patos PB 2003 PB/PE-B AB206427 [6]

BRbv258(BR-Pbv8) Cattle Patos PB 2003 PB/PE-B AB206428 [6]

BRbv260(BR-Pbv10) Cattle Patos PB 2003 PB/PE-B AB206429 [6]

BRbv261(BR-Pbv11) Cattle Patos PB 2003 PB/PE-B AB206430 [6]

BRbv262(BR-Pbv12) Cattle Patos PB 2003 PB/PE-B AB206431 [6]

BRbv279 Cattle Pirapozinho SP 2002 AB675614*4 [9]

BRbv312 Cattle Paulo de Frontin RJ 1987 AB675615 This study

BRbv316 Cattle Miguel Pereina RJ 2000 AB675616*4 [9]

BRbv324 Cattle Itapecuru Mirim MA 2004 AB675617*4 [9]

BRbv340 Cattle Nossa Senhora do Livramento MT 2004 AB675618*4 [9]

BRbv382 Cattle Orizona GO 2002 AB675619*4 [9]

BRbv384 Cattle Nova América GO 2002 AB675620*4 [9]

BRbv403 Cattle Piranhas GO 2002 AB675621*4 [9]

BRbv581 Cattle Tambaú SP 2003 AB675622*4 [9]

BRbv617 Cattle Rio Claro RJ 2004 AB675623*4 [9]

BRbv645 Cattle Capinzal do Norte MA 2004 AB675624*4 [9]

BRbv668 Cattle Santo Antônio dos Lopes MA 2005 AB675625*4 [9]

BRbv670 Cattle Godofredo Viana MA 2005 AB675626*4 [9]

BRbv792 Cattle Morrinhos GO 2002 AB675627*4 [9]

BRbv804 Cattle Pilar de Goiás GO 2005 AB675628*4 [9]

BRbv827 Cattle Cocalzinho de Goiás GO 2005 AB675629*4 [9]

BRbv844 Cattle Itapaci GO 2006 AB675630*4 [9]

BRbv934 Cattle Bandeirantes MS 2005 AB675631*4 [9]

BRbv1169 Cattle Patos PB 2004 PB/PE-B AB623080 This study

BRbv1170 Cattle Santa Terezinha PB 2004 PB/PE-B AB623081 This study

BRbv1172 Cattle São José do Bonfim PB 2004 PB/PE-B AB623082 This study

BRbv1173 Cattle Itaporanga PB 2004 PB/PE-A AB623083 This study

BRbv1174 Cattle São Vicente do Seridó PB 2004 PB/PE-B AB623084 This study

BRbv1176 Cattle Patos PB 2005 PB/PE-B AB623085 This study

BRbv1177 Cattle Santa Luzia PB 2005 PB/PE-B AB623086 This study

BRbv1179 Cattle Areal PB 2006 PB/PE-B AB623087 This study

BRbv1181 Cattle Monteiro PB 2006 PB/PE-B AB623089 This study

BRbv1182 Cattle Junco do Seridó PB 2006 PB/PE-B AB623090 This study

BRbv1183 Cattle São José do Sabugi PB 2006 PB/PE-B AB623091 This study

BRbv1184 Cattle Santa Luzia PB 2006 PB/PE-B AB623092 This study

BRbv1186 Cattle Patos PB 2007 PB/PE-B AB623093 This study

BRbv1187 Cattle Patos PB 2007 PB/PE-B AB623094 This study

BRbv1190 Cattle Areal PB 2007 PB/PE-B AB623096 This study

BRbv1193 Cattle Patos PB 2007 PB/PE-B AB623097 This study

BRbv1194 Cattle São José do Bonfim PB 2007 PB/PE-B AB623098 This study

BRbv1197 Cattle São José do Bonfim PB 2007 PB/PE-B AB623099 This study

BRbv1198 Cattle Brejinho PE 2007 PB/PE-B AB623106 This study

BRbv1199 Cattle Patos PB 2008 PB/PE-B AB623100 This study

BRbv1200 Cattle Patos PB 2008 PB/PE-B AB623101 This study

BRbv1201 Cattle Patos PB 2008 PB/PE-B AB623102 This study

BRbv1204 Cattle Patos PB 2008 PB/PE-B AB623103 This study

BRbv1206 Cattle Patos PB 2008 PB/PE-B AB623104 This study

BRbv1207 Cattle Patos PB 2009 PB/PE-B AB623105 This study

BRbv1209 Cattle Vitória de Santo Antão PE 2008 PB/PE-B AB623107 This study

BRbv1210 Cattle Venturosa PE 2008 PB/PE-A AB623108 This study

BRbv1211 Cattle Pedra PE 2008 PB/PE-A AB623109 This study

BRbv1212 Cattle Venturosa PE 2008 PB/PE-A AB623110 This study

BRbv1213 Cattle Garanhuns PE 2008 PB/PE-A AB623111 This study

BRbv1214 Cattle Venturosa PE 2008 PB/PE-A AB623112 This study

BRbv1215 Cattle Paranatama PE 2008 PB/PE-B AB623113 This study

BRbv1216 Cattle Venturosa PE 2008 PB/PE-A AB623114 This study

BRbv1217 Cattle Belo Jardim PE 2008 PB/PE-B AB623115 This study

BRbv1218 Cattle Belo Jardim PE 2009 PB/PE-B AB623116 This study

BRbv1219 Cattle Lajedo PE 2009 PB/PE-B AB623117 This study

BRbv1220 Cattle Garanhuns PE 2009 PB/PE-A AB623118 This study

BRgt249(BR-Pgt1) Goat Patos PB 2003 PB/PE-B AB206437 [6]

BRgt1205 Goat São Mamede PB 2008 PB/PE-B AB623077 This study

BRhr31 Horse Ipora GO 1998 AB083804 [17]

BRhr1196 Horse Patos PB 2007 PB/PE-B AB623076 This study

BRsp250(BR-Psp1) Sheep Patos PB 2003 PB/PE-B AB206438 [6]

BRsp1171 Sheep Santa Terezinha PB 2004 PB/PE-B AB623078 This study

BRsp1203 Sheep Patos PB 2008 PB/PE-B AB623079 This study

*1 Names in parentheses are designations from Shoji et al. (2006)

*2 State abbreviations are as follows: PB Paraíba, PE Pernambuco, GO Goiás, SP São Paulo, RJ Rio de Janeiro, MT Mato Grosso, TO Tocantins, MA Maranhão, PA Pará, MS Mato Grosso do Sul

*3 Lineages are based on the phylogenetic tree of Figure 1

*4 We determined extra sequences in this study

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

NM performed the molecular genetic studies and edited the manuscript; HK performed the RT-PCR and sequencing; TI, JABA, MLCRS, FHI, and TS participated in the study design, management, and coordination, and assisted in drafting the manuscript. All authors read and approved the final manuscript.

Contributor Information

Nobuyuki Mochizuki, Email: mochizuki.nobuyuki@gmail.com.

Hiroyuki Kawasaki, Email: hkat@i-revo.ne.jp.

Maria LCR Silva, Email: luacristiny@yahoo.com.br.

José AB Afonso, Email: afonsojab@oi.com.br.

Takuya Itou, Email: itou.takuya@nihon-u.ac.jp.

Fumio H Ito, Email: fumio@usp.br.

Takeo Sakai, Email: sakai.takeo@nihon-u.ac.jp.

Acknowledgements

This work was supported in part by a Grant-in-Aid for the Academic Frontier Project for Private Universities from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

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