Genetic characterization and geographic distribution of rabies virus isolates in Brazil: identification of two reservoirs, dogs and vampire bats

Fifty Years of the National Rabies Control Program in Brazil under the One Health Perspective

In 1973, the National Rabies Program was created in Brazil through an agreement between the Ministry of Health and Agriculture. Since its beginning, it developed integrated action through access to free post-exposure prophylaxis (PEP) for people at risk, dog vaccination campaigns, a joint surveillance system, and awareness. This study aims to describe human rabies in Brazil under the One Health perspective in recent decades, including achievements in the control of dog-mediated cases and challenges in human cases transmitted by wild animals. This paper also explores possible drivers of human rabies in the Northeast Region with half of the cases. The first part of this study was descriptive, presenting data and examples by periods. Statistical analysis was performed in the last period (2010-2022) to explore possible drivers. Dog-mediated human cases decreased from 147 to 0, and dog cases decreased from 4500 to 7. A major challenge is now human cases transmitted by wild animals (bats, non-human primates, and wild canids). Most current human cases occur in municipalities with a tropical and subtropical moist broadleaf forest biome and a Gini index higher than 0.5. In the multivariable analysis, an association with temperature was estimated (OR = 1.739; CI95% = 1.181-2.744), and primary healthcare coverage (OR = 0.947; CI95% = 0.915-0.987) was identified as a protector. It is possible to significantly reduce the number of dog-mediated human rabies cases through the efforts presented. However, Brazil has wildlife variants of the rabies virus circulating. The association of human cases with higher temperatures in the Northeast is a concern with climate change. To reduce human cases transmitted by wild animals, it is important to continue distributing free PEP, especially in remote at-risk areas in the Amazon Region, and to increase awareness.

A review of the diet of the common vampire bat (Desmodus rotundus) in the context of anthropogenic change

The common vampire bat (Desmodus rotundus) maintains a diverse, sanguivorous diet, utilizing a broad range of prey taxa. As anthropogenic change alters the distribution of this species, shifts in predator-prey interactions are expected. Understanding prey richness and patterns of prey selection is, thus, increasingly informative from ecological, epidemiological, and economic perspectives. We reviewed D. rotundus diet and assessed the geographical, taxonomical, and behavioral features to find 63 vertebrate species within 21 orders and 45 families constitute prey, including suitable host species in regions of invasion outside D. rotundus' range. Rodentia contained the largest number of species utilized by D. rotundus, though cattle were the most commonly reported prey source, likely linked to the high availability of livestock and visibility of bite wounds compared to wildlife. Additionally, there was tendency to predate upon species with diurnal activity and social behavior, potentially facilitating convenient and nocturnal predation. Our review highlights the dietary heterogeneity of D. rotundus across its distribution. We define D. rotundus as a generalist predator, or parasite, depending on the ecological definition of its symbiont roles in an ecosystem (i.e., lethal vs. non-lethal blood consumption). In view of the eminent role of D. rotundus in rabies virus transmission and its range expansion, an understanding of its ecology would benefit public health, wildlife management, and agriculture.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42991-023-00358-3.

Sequence analysis of nucleoprotein gene reveals the co-circulation of lineages and sublineages of rabies virus in herbivorous in Rio Grande do Sul state, Brazil

An unprecedented outbreak of rabies occurred in Rio Grande do Sul state (RS) from 2012 onward, resulting in thousands of bovine deaths, important economic losses, and posing risk to human health. This article describes a genetic analysis of 145 rabies viruses (RABV) recovered from herbivorous from RS between 2012 and 2017, based on partial sequence analysis of the nucleoprotein (N) gene. High nucleotide (nt) identity (95.5 to 100%) and amino acid (aa) similarity (96.7 to 100%) were observed among the analyzed sequences. These sequences displayed a high sequence nt identity/aa similarity with bovine RABV sequences (96.4-97.9%; 98.1-100%, respectively) and vampire bat RABV sequences (96.3-97.5%; 97.8-99.5%). Phylogenetic analyzes based on the N sequence allowed for the segregation of viruses into two distinct clusters. Cluster 1 comprised RABV sequences covering the whole studied period, whereas cluster 2 grouped a lower number of viruses from 2013, 2014, 2015, to 2017. In some cases, viruses obtained from the same region within a short period of time grouped to distinct clusters or sub-clusters, indicating the co-circulation of distinct virus lineages in these outbreaks. The segregation into sub-clusters was also observed for viral sequences obtained from the same region at different times, indicating the involvement of distinct viruses. In summary, partial sequence analyses revealed a high conservation of N protein and the circulation of two lineages and different sublineages of RABV in the region. In addition, our results confirm the suitability of N gene to study the genetic relationships among RABV isolates.

Phylogenetic analysis of near full-length sequences of the Desmodus rotundus genetic lineage of rabies virus

The World Health Organization (WHO), reports that rabies causes tens of thousands of deaths every year killing humans, non-human primates and other animals. Rabies continues to be a public health issue, despite the existence of effective vaccines. The dogs remain the primary reservoir and transmitter of rabies to humans globally. In the Americas, bats are regarded as the second most common source of rabies virus to humans. The vampire bat Desmodus rotundus has been identified as a natural reservoir of rabies virus (RABV) in this region. The complete genome of the RABV variant maintained by populations of vampire bats D. rotundus has rarely been reported. In this study, we sequenced and analyzed the genome of a RABV variant detected in D. rotundus. The sample, collected from an endemic area in São Paulo State, was phylogenetically compared with the genome of the standard sample for species Rabies virus as well as other samples belonging to terrestrial and bat-associated cycles of rabies transmission, available in GenBank. Distinct patterns linked to the genetic lineage were identified. These data can aid in the understanding of the molecular epidemiology of this virus and the epidemiological importance of this species in the transmission of the RABV.

Glycoprotein-G-gene-based molecular and phylogenetic analysis of rabies viruses associated with a large outbreak of bovine rabies in southern Brazil

A large outbreak of hematophagous-bat-associated bovine rabies has been occurring in Rio Grande do Sul (RS), the southernmost Brazilian state, since 2011, with official estimates exceeding 50,000 cattle deaths. The present article describes a genetic characterization of rabies virus (RABV) recovered from 59 affected cattle and two sheep, from 56 herds in 16 municipalities (2012-2016). Molecular analysis was performed using the nucleotide (nt) and predicted amino acid (aa) sequences of RABV glycoprotein G (G). A high level of nt and aa sequence identity was observed among the examined G sequences, ranging from 98.4 to 100%, and from 97.3 to 100%, respectively. Likewise, high levels of nt and aa sequence identity were observed with bovine (nt, 99.8%; aa, 99.8%) and hematophagous bat (nt, 99.5%; aa, 99.4%) RABV sequences from GenBank, and lower levels were observed with carnivore RABV sequences (nt, 92.8%; aa, 88.1%). Some random mutations were observed in the analyzed sequences, and a few consistent mutations were observed in some sequences belonging to cluster 2, subcluster 2b. The clustering of the sequences was observed in a phylogenetic tree, where two distinct clusters were evident. Cluster 1 comprised RABV sequences covering the entire study period (2012 to 2016), but subclusters corresponding to different years could be identified, indicating virus evolution and/or introduction of new viruses into the population. In some cases, viruses from the same location obtained within a short period grouped into different subclusters, suggesting co-circulation of viruses of different origins. Subcluster segregation was also observed in sequences obtained in the same region during different periods, indicating the involvement of different viruses in the cases at different times. In summary, our results indicate that the outbreaks occurring in RS (2012 to 2016) probably involved RABV of different origins, in addition to a possible evolution of RABV isolates within this period.

Antigenic and genotypic characterization of rabies virus isolated from bats (Mammalia: Chiroptera) from municipalities in São Paulo State, Southeastern Brazil

Bats have aroused growing attention in the public health sphere because they are considered the main reservoir of rabies virus (RABV) in the Americas, in places where canine rabies is under control. Antigenic and genetic studies of RABV isolates have been used to describe the epidemiological profile of rabies and to identify possible hosts/reservoirs for different epidemiological cycles. This study describes the antigenic and genotypic characterization of 19 RABV isolates from central nervous system samples of non-hematophagous bats (Mammalia: Chiroptera). These bats were diagnosed as RABV positive by direct fluorescent antibody and mouse inoculation tests. Antigenic characterization using a panel of eight monoclonal antibodies revealed that 7 of 19 RABV isolates from these bats belonged to variant 3, for which the hematophagous bat species Desmodus rotundus is the main reservoir, and 1 of 19 RABV isolates from an insectivorous bat belonged to variant 4, which is characteristic of these bats. The remaining 11 RABV samples were divided into six non-compatible profiles. The isolates were subjected to reverse transcription polymerase chain reaction for the N gene and partially sequenced. Genetic characterization of these isolates was performed by grouping the sequences obtained with known RABV lineages. The sequences were grouped in clusters by the phylogenetic inference neighbor-joining method, together with another 89 homologous sequences obtained from GenBank. This analysis grouped the isolates into four known lineages: Nyctinomops Brazil, Myotis Brazil, Eptesicus Brazil and D. rotundus Brazil, as well as another cluster that may define a RABV lineage not yet characterized, here named Myotis Brazil II, for which bats of the genus Myotis apparently act as reservoirs. This assumption of a new lineage is also based on the observation of amino acid substitutions, with an average intraspecific identity of 99.8%, varying from 99.6 to 100.0% for nucleotides and 100.0% for amino acids.

Molecular epidemiological tracing of a cattle rabies outbreak lasting less than a month in Rio Grande do Sul in southern Brazil

Background

Vampire bat-transmitted cattle rabies cases are typically encountered in areas where the disease is endemic. However, over the period of a month in 2009, an outbreak of cattle rabies occurred and then ended spontaneously in a small area of the Rio Grande do Sul State in southern Brazil. To investigate the epidemiological characteristics of this rabies outbreak in Rio Grande do Sul, 26 nucleotide sequences of rabies virus (RABV) genomes that were collected in this area were analyzed phylogenetically.

Results

Nucleotide sequence identities of the nucleoprotein gene and G–L intergenic region of the 26 RABVs were greater than 99.6 %. Phylogenetic analysis showed that all RABVs clustered with the vampire bat-related cattle RABV strains and that the RABVs were mainly distributed in southern Brazil.

Conclusions

The findings of the present study suggested that a small population of rabid vampire bats carrying a single RABV strain produced a spatiotemporally restricted outbreak of cattle rabies in southern Brazil.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-1898-5) contains supplementary material, which is available to authorized users.

The Importance of Wild Canids in the Epidemiology of Rabies in Northeast Brazil: A Retrospective Study

Rabies is an endemic disease in Brazil, where it is considered a serious public health problem. Although the number of human and dog-transmitted cases has declined in recent decades, rabies in wildlife has emerged considerably. Among the sylvatic animals, wild canids have been considered important hosts of the rabies virus. We performed a retrospective study of reported cases of rabies in wild canids and human victims in Ceará state (Northeast Brazil) during 2003 to 2013. Information was provided by governmental laboratories involved in rabies detection and by the Ministry of Health. From January 2003 to December 2013, a total of 11 931 animal samples were examined for rabies. Positivity were detected in 438 samples (3.67%), of which 229 (52.28%) were domestic animals, 105 (23.97%) wild canids and 104 (23.74%) other wild animals (bats, marmosets and raccoons). Approximately 33% of wild canids surveyed (n = 317) were positive for rabies. During the studied period, a total of 1923 attacks on humans by wild canids were registered. Males (n = 1405) were more affected than females (n = 520; 72.98% versus 27.01%), and the median age of all cases was 36.5 years. Injuries to individuals up to 19 years old corresponded to approximately 30% (n = 565) of all cases. Most of the victims lived in rural areas (72.46%; n = 1395), and the majority showed bites (81.13%; n = 1677) or scratches (12.23%; n = 253). Injuries were considered profound (52.1%; n = 1003), superficial (40.91; n = 788) or multiple with severe laceration (6.98%; n = 134). Only 1300 (67.53%) victims were enrolled for the complete rabies post-exposure prophylaxis scheme. Data from the present study confirm that wild canids are important hosts of rabies virus in northeastern Brazil and jeopardize rabies control in this area. Local authorities should focus their efforts in education of health professionals. In addition, strategies should be formulated to preserve wildlife.

Profile of Cytokines and Chemokines Triggered by Wild-Type Strains of Rabies Virus in Mice

Rabies is a lethal infectious disease that causes 55,000 human deaths per year and is transmitted by various mammalian species, such as dogs and bats. The host immune response is essential for avoiding viral progression and promoting viral clearance. Cytokines and chemokines are crucial in the development of an immediate antiviral response; the rabies virus (RABV) attempts to evade this immune response. The virus's capacity for evasion is correlated with its pathogenicity and the host's inflammatory response, with highly pathogenic strains being the most efficient at hijacking the host's defense mechanisms and thereby decreasing inflammation. The purpose of this study was to evaluate the expression of a set of cytokine and chemokine genes that are related to the immune response in the brains of mice inoculated intramuscularly or intracerebrally with two wild-type strains of RABV, one from dog and the other from vampire bat. The results demonstrated that the gene expression profile is intrinsic to the specific rabies variant. The prompt production of cytokines and chemokines seems to be more important than their levels of expression for surviving a rabies infection.

Trends in animal rabies surveillance in the endemic state of Minas Gerais, Brazil

Rabies is a viral zoonosis affecting mammal species and causes large economic losses. Included among the neglected diseases, it is still insufficiently addressed by governments and the international community, despite formal surveillance and control programs. This study used a dataset of 10,112 rabies diagnoses in animals provided by the Brazilian passive surveillance system from 2001 to 2012. The positivity rate of the tested samples was 26.4%, and a reduction in the total samples sent during the last six years was observed. The kernel density map indicated case concentration in the south region and a decrease in density of rabies cases in the second period studied (2007 to 2012). The directional trend of positive rabies diagnoses remained in the south region, as shown by the standard deviational ellipse. The spatial scan statistic identified three large clusters of positive diagnoses, one in the first period (2001-2006) and two in the second period (2007-2012), indicating an expansion of risk areas. The decrease in rabies cases from 2006 to 2012 does not necessarily reflect lower viral circulation or improvement in actions by epidemiological surveillance; this decrease could indicate a deficiency in epidemiological surveillance during the observation period due to the increase in the silent areas. Surveillance should maintain an increasing or constant number of tests during the years in addition to a reduction in the number of outbreaks of rabies, which would indicate a lower positivity rate. The findings in this study indicate deterioration in the effectiveness of the passive surveillance for rabies. The number of rabies cases, total number of tests performed and positivity rate are good indicators for evaluating passive surveillance. This paper can function as a guide for the assessment and improvement of the actions in passive surveillance of rabies.

Phylodynamics of vampire bat-transmitted rabies in Argentina

Common vampire bat populations distributed from Mexico to Argentina are important rabies reservoir hosts in Latin America. The aim of this work was to analyse the population structure of the rabies virus (RABV) variants associated with vampire bats in the Americas and to study their phylodynamic pattern within Argentina. The phylogenetic analysis based on all available vampire bat-related N gene sequences showed both a geographical and a temporal structure. The two largest groups of RABV variants from Argentina were isolated from northwestern Argentina and from the central western zone of northeastern Argentina, corresponding to livestock areas with different climatic, topographic and biogeographical conditions, which determined their dissemination and evolutionary patterns. In addition, multiple introductions of the infection into Argentina, possibly from Brazil, were detected. The phylodynamic analysis suggests that RABV transmission dynamics is characterized by initial epizootic waves followed by local enzootic cycles with variable persistence. Anthropogenic interventions in the ecosystem should be assessed taking into account not only the environmental impact but also the potential risk of disease spreading through dissemination of current RABV lineages or the emergence of novel ones associated with vampire bats.

Isolation of a phylogenetically distinct rabies virus from a tufted capuchin monkey (Cebus apella) in Brazil

A rabies virus isolate (BRmk1358 strain) was discovered from a rabid tufted capuchin monkey in Brazil. The present study determined the nucleotide sequence of the BRmk1358 strain and compared with the rabies viruses isolated from marmosets and other animals in the Americas. Phylogenetic analyses showed that the BRmk1358 strain formed a lineage distant from that of marmoset rabies virus within the Chiroptera-related rabies virus cluster. This result suggests that the source of rabies infection in the tufted capuchin monkey may have been bat, and that they have a risk to act as rabies reservoir in Brazil.

Biotechnology advances: a perspective on the diagnosis and research of Rabies Virus

Rabies is a widespread zoonotic disease responsible for approximately 55,000 human deaths/year. The direct fluorescent antibody test (DFAT) and the mouse inoculation test (MIT) used for rabies diagnosis, have high sensitivity and specificity, but are expensive and time-consuming. These disadvantages and the identification of new strains of the virus encourage the use of new techniques that are rapid, sensitive, specific and economical for the detection and research of the Rabies Virus (RABV). Real-time RT-PCR, phylogeographic analysis, proteomic assays and DNA recombinant technology have been used in research laboratories. Together, these techniques are effective on samples with low virus titers in the study of molecular epidemiology or in the identification of new disease markers, thus improving the performance of biological assays. In this context, modern advances in molecular technology are now beginning to complement more traditional approaches and promise to revolutionize the diagnosis of rabies. This brief review presents some of the recent molecular tools used for RABV analysis, with emphasis on rabies diagnosis and research.

Epidemiology

This chapter provides an overview of the global epidemiology of rabies, focusing on major changes over the past half-century and highlighting recent discoveries. This chapter also describes the natural and iatrogenic routes of transmission, as well as the risk and necessary actions for the prevention of rabies following an exposure. It reviews the methods for rabies diagnosis and the biologics for prevention, in addition to differences in rabies prophylaxis recommendations among advisory committees. The chapter also considers epidemiology and trends in global human rabies and the dynamics of the corresponding mammalian reservoir hosts for each area. Furthermore, it considers the phylogenetics of rabies virus, other lyssaviruses, and specific rabies virus variants in the context of regional rabies and the potential for novel emergences. Special attention is paid to developed countries, where existing surveillance and diagnostic infrastructure have provided detailed insights into the nature changing patterns in rabies epidemiology-patterns expected to be increasingly relevant to other less-developed nations based on current trends. Special attention is afforded to canine rabies, as dogs remain responsible for over 99% of all human exposures to the virus, including the methods and problems associated with intentional and unintentional movement of dogs at national and international levels. Finally, the chapter discusses the economic burden of rabies in terms of human and infrastructure support.

Desmodus rotundus and Artibeus spp. bats might present distinct rabies virus lineages

In Brazil, bats have been assigned an increasing importance in public health as they are important rabies reservoirs. Phylogenetic studies have shown that rabies virus (RABV) strains from frugivorous bats Artibeus spp. are closely associated to those from the vampire bat Desmodus rotundus, but little is known about the molecular diversity of RABV in Artibeus spp. The N and G genes of RABV isolated from Artibeus spp. and cattle infected by D. rotundus were sequenced, and phylogenetic trees were constructed. The N gene nucleotides tree showed three clusters: one for D. rotundus and two for Artibeus spp. Regarding putative N amino acid-trees, two clusters were formed, one for D. rotundus and another for Artibeus spp. RABV G gene phylogeny supported the distinction between D. rotundus and Artibeus spp. strains. These results show the intricate host relationship of RABV's evolutionary history, and are invaluable for the determination of RABV infection sources.

Phylogenetic analysis of partial RNA-polymerase blocks II and III of Rabies virus isolated from the main rabies reservoirs in Brazil

This study describes the results of the sequencing and analysis of segments of Blocks II and III of the RNA polymerase L gene of Rabies virus isolates from different reservoir species of Brazil. The phylogenetic relations of the virus were determined and a variety of species-specific nucleotides were found in the analyzed areas, but the majority of these mutations were found to be synonymous. However, an analysis of the putative amino acid sequences were shown to have some characteristic mutations between some reservoir species of Brazil, indicating that there was positive selection in the RNA polymerase L gene of Rabies virus. On comparing the putative viral sequences obtained from the Brazilian isolates and other Lyssavirus, it was determined that amino acid mutations occurred in low-restriction areas. This study of the L gene of Rabies virus is the first to be conducted with samples of virus isolates from Brazil, and the results obtained will help in the determination of the phylogenetic relations of the virus.

One-step protocol for amplification of near full-length cDNA of the rabies virus genome

Full-length genome sequencing of the rabies virus is not a routine laboratory procedure. To understand fully the epidemiology, genetic variation and evolution of the rabies virus, full-length viral genomes need to be obtained. For rabies virus studies, cDNA synthesis is usually performed using nonspecific oligonucleotides followed by cloning. When specific primers are used, the cDNA obtained is only partial and is limited to the coding regions. Therefore, the development of methods for synthesizing long cDNA using rabies virus-specific primers is of fundamental importance. A new protocol for the synthesis of long cDNA and the development of 19 new primers are described in this study. This procedure allowed the efficient amplification of the full-length genome of the rabies virus variant maintained by hematophagous bat (Desmodus rotundus) populations following the synthesis of a complete long cDNA. Partial sequencing of the rabies virus genome was performed to confirm rabies-specific PCR amplification. Because degenerate primers were employed, this technique can be adapted easily to other variants. Importantly, this new method is faster and less expensive than cloning methods.

Raiva em bovinos na Região Sul do Rio Grande do Sul: epidemiologia e diagnóstico imuno-histoquímico

Foi realizado um estudo retrospectivo de casos de raiva paralítica em bovinos na área de influência do Laboratório Regional de Diagnóstico (LRD) da Faculdade de Veterinária, Universidade Federal de Pelotas (UFPel), ocorridos em 1978-2007. Foram estudados também 11 surtos de raiva observados em 2008-2010, na mesma região. Neste período morreram 42 animais de um total de 686 sob risco. A idade dos animais foi de 1-6 anos e o curso clínico de 4-14 dias. No estudo retrospectivo de 1978-2007 foram identificados 77 surtos ou casos isolados de raiva paralítica em bovinos. A morbidade em todos os surtos diagnosticados em 1978-2010 variou de 0,37% a 20%. Vinte e quatro casos ocorreram no outono, sete na primavera, 14 no verão e 16 no inverno. O diagnóstico foi realizado pela epidemiologia, sinais clínicos e lesões histológicas observadas. No estudo dos casos de raiva paralítica em bovinos ocorridos a partir de 2008, o diagnóstico foi confirmado pela técnica de imuno-histoquímica utilizando anticorpo policlonal anti-virus rábico. Em dois destes casos não foi observada meningoencefalite não-supurativa, porém a imuno-histoquímica demonstrou a presença do antígeno viral. Esta técnica é uma importante ferramenta para o diagnóstico de raiva, devendo ser utilizada em todos os casos suspeitos nos quais não se evidenciam lesões de encefalite.

[The bats and rabies in the Western region of the State of São Paulo, Brazil]

INTRODUCTION

The Polo da Alta Sorocabana Laboratory in Presidente Prudente, SP, in partnership with other research institutions, conducted studies related to bats from the western region of the State of Sao Paulo, Brazil. Thus, certain situations were investigated, including: a) isolation of the rabies virus from 2006 to 2008; b) identification of respective antigenic variants; and c) characterization of daytime shelters of Desmodus rotundus vampire bats.

METHODS

Samples for examination originated from nonhematophagous bats forwarded to the laboratory and subjected to direct fluorescent antibody test and mouse inoculation test. Positive samples were characterized by the monoclonal antibody test. Regarding the bats, they were identified and classified and mapping of their shelters was also performed.

RESULTS

The laboratory received 1,113 nonhematophagous bats for rabies diagnosis, 11 (1%) of which were positives, and among the positive samples, 5 (45.5%) presented antigenic variant 3 (from the bat Desmodus rotundus) and 4 (36.5%) were compatible with samples derived from Brazilian insectivorous bats. Sixteen vampire bat shelters were investigated and observation confirmed the presence of another 3 species of nonhematophagous bats coexisting with them.

CONCLUSIONS

The experiments showed that at least 3 antigenic variants of rabies virus are circulating in the region and that the cohabitation of vampire bats with nonhematophagous bats could be related to the dissemination of the rabies virus.

Pathogenicity of different rabies virus isolates and protection test in vaccinated mice

This study was aimed to evaluate and compare the pathogenicity of rabies virus isolated from bats and dogs, and to verify the efficacy of a commercial rabies vaccine against these isolates. For evaluation of pathogenicity, mice were inoculated by the intramuscular route (IM) with 500MICLD50/0.03mL of the viruses. The cross-protection test was performed by vaccinating groups of mice by the subcutaneous route and challenged through the intracerebral (IC) route. Isolates were fully pathogenic when inoculated by the IC route. When inoculated intramuscularly, the pathogenicity observed showed different death rates: 60.0% for the Desmodus rotundus isolate; 50.0% for dog and Nyctinomops laticaudatus isolates; 40.0% for Artibeus lituratus isolate; 9.5% Molossus molossus isolate; and 5.2% for the Eptesicus furinalis isolate. Mice receiving two doses of the vaccine and challenged by the IC route with the isolates were fully protected. Mice receiving only one dose of vaccine were partially protected against the dog isolate. The isolates from bats were pathogenic by the IC route in mice. However, when inoculated through the intramuscular route, the same isolates were found with different degrees of pathogenicity. The results of this work suggest that a commercial vaccine protects mice from infection with bat rabies virus isolates, in addition to a canine rabies virus isolate.

[Host specificity of viruses and inter-species crossing]

Most viruses are host-specific and thus, they are closely associated to an animal species. This host specificity is conditioned by the cell susceptibility to the virus, given by the host cell receptors, and by the cell permissivity that relies on the availability of cellular factors required for viral replication. However, for many viruses, this host specificity is not absolute and inter-species transmissions are possible. Viruses which can be transmitted from an animal reservoir to humans are responsible for zoonotic diseases. Human activities and their impact on the natural environment dramatically contribute to emergence of zoonoses. Selection of viral mutations that confer better adaptation of animal viruses to humans may lead to epidemic spread of these diseases.

A method for simultaneous detection and identification of Brazilian dog- and vampire bat-related rabies virus by reverse transcription loop-mediated isothermal amplification assay

At present, the sporadic occurrence of human rabies in Brazil can be attributed primarily to dog- and vampire bat-related rabies viruses. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) was employed as a simultaneous detection method for both rabies field variants within 60 min. Vampire bat-related rabies viruses could be distinguished from dog variants by digesting amplicons of the RT-LAMP reaction using the restriction enzyme AlwI. Amplification and digestion could both be completed within 120 min after RNA extraction. In addition, the RT-LAMP assay also detected rabies virus in isolates from Brazilian frugivorous bats and Ugandan dog, bovine and goat samples. In contrast, there were false negative results from several Brazilian insectivorous bats and all of Chinese dog, pig, and bovine samples using the RT-LAMP assay. This study showed that the RT-LAMP assay is effective for the rapid detection of rabies virus isolates from the primary reservoir in Brazil. Further improvements are necessary so that the RT-LAMP assay can be employed for the universal detection of genetic variants of rabies virus in the field.

Comparative analysis of rabies virus isolates from Brazilian canids and bats based on the G gene and G-L intergenic region

Rabies virus (RABV) isolates from two species of canids and three species of bats were analyzed by comparing the C-terminal region of the G gene and the G-L intergenic region of the virus genome. Intercluster identities for the genetic sequences of the isolates showed both regions to be poorly conserved. Phylogenetic trees were generated by the neighbor-joining and maximum parsimony methods, and the results were found to agree between the two methods for both regions. Putative amino acid sequences obtained from the G gene were also analyzed, and genetic markers were identified. Our results suggest that different genetic lineages of RABV are adapted to different animal species in Brazil.

Caracterização molecular do vírus da raiva isolado de Desmodus rotundus capturados no Estado do Rio de Janeiro

Caracterizou-se filogeneticamente o vírus da raiva, isolado de morcegos hematógafos (Demodus rotundus). Cento e noventa e nove D. rotundus foram capturados em cinco abrigos, no Norte e Noroeste do Estado do Rio de Janeiro e sul do Espírito Santo. Sete deles foram positivos para a raiva. Amostras desses vírus foram sequenciadas e comparadas com sequências provenientes de diversos estados brasileiros. As sequências de vírus da raiva isoladas, na região norte do Estado do Rio de Janeiro, mostraram características que as distinguem de amostras de vírus isoladas em outras regiões do país, no entanto foram idênticas às isoladas de bovinos no noroeste do Rio de Janeiro.

Updated list of bat species positive for rabies in Brazil

This paper presents an updated list of bat species positive for rabies in Brazil. It was developed based on database research via the internet, of international and national literature and annals of the most important technical and scientific meetings related to rabies and chiroptera in Brazil from 1996 to 2009. The new list of rabies positive bats consists of 41 species, belonging to 25 genera and three families: Phyllostomidae 43.9%, Vespertilionidae 29.3% and Molossidae 26.8%. In addition, questions were raised regarding the lack of data, including sex, age, circumstances and location of bat capture and incomplete and outdated species identification. Results of genetic and antigenic studies performed on Brazilian rabies positive bats were shown.

Perfil antigênico do vírus da raiva isolado de diferentes espécies de morcegos não hematófagos da Região de Presidente Prudente, Estado de São Paulo

O Laboratório de Virologia Clínica e Molecular do Instituto de Ciências Biomédicas da Universidade de São Paulo, utilizando-se da técnica de anticorpos monoclonais, tipificou 18 amostras de vírus rábico provenientes de morcegos não hematófagos de várias espécies provenientes da Região de Presidente Prudente, SP, Brasil. Destas amostras, 15 (82,3%) foram definidas como variante 3 (compatível com amostras isoladas de morcegos Desmodus rotundus) e 3 (16,7%) como variante 4 (compatível com amostras isoladas de morcegos Tadarida brasiliensis).

Molecular and geographic analyses of vampire bat-transmitted cattle rabies in central Brazil

Background

Vampire bats are important rabies virus vectors, causing critical problems in both the livestock industry and public health sector in Latin America. In order to assess the epidemiological characteristics of vampire bat-transmitted rabies, the authors conducted phylogenetic and geographical analyses using sequence data of a large number of cattle rabies isolates collected from a wide geographical area in Brazil.

Methods

Partial nucleoprotein genes of rabies viruses isolated from 666 cattle and 18 vampire bats between 1987 and 2006 were sequenced and used for phylogenetic analysis. The genetic variants were plotted on topographical maps of Brazil.

Results

In this study, 593 samples consisting of 24 genetic variants were analyzed. Regional localization of variants was observed, with the distribution of several variants found to be delimited by mountain ranges which served as geographic boundaries. The geographical distributions of vampire-bat and cattle isolates that were classified as the identical phylogenetic group were found to overlap with high certainty. Most of the samples analyzed in this study were isolated from adjacent areas linked by rivers.

Conclusion

This study revealed the existence of several dozen regional variants associated with vampire bats in Brazil, with the distribution patterns of these variants found to be affected by mountain ranges and rivers. These results suggest that epidemiological characteristics of vampire bat-related rabies appear to be associated with the topographical and geographical characteristics of areas where cattle are maintained, and the factors affecting vampire bat ecology.

Ocorrência de raiva em ovinos no Rio Grande do Sul

Descreve-se a ocorrência de raiva em ovinos na região Central do Rio Grande do Sul em novembro de 2003. Foram afetados dois ovinos de raça mista, um macho de três meses e uma fêmea de 2,5 anos de idade que apresentaram sinais clínicos com evolução de cinco dias e caracterizados por dificuldade de locomoção, tremores musculares, decúbito lateral, convulsões, opistótono e febre. Histologicamente havia mielomeningoencefalite não-supurativa, associada a inclusões eosinofílicas intracitoplasmáticas (corpúsculos de Negri) em neurônios nos dois ovinos afetados. Em um ovino em que o gânglio de Gasser foi examinado, havia ganglionite não-supurativa. As lesões concentravam-se predominantemente na substância cinzenta da medula espinhal, no tronco encefálico e no cerebelo. Antígeno viral foi detectado em seções selecionadas de ponte e bulbo submetidas ao teste de imuno-histoquímica utilizando anticorpo policlonal anti-ribonucleoproteína do vírus da raiva. Os casos ocorreram em meio a um surto de raiva bovina transmitida por morcegos e foram considerados, com bases epidemiológicas, como transmitidos da mesma forma, como ocorre na raiva endêmica de bovinos no Rio Grande do Sul.

Characterization of Rabies virus isolated from canids and identification of the main wild canid host in Northeastern Brazil

The rabies cases in dogs and wild canids in Northeastern Brazil are a public and animal health problem. This paper describes the identities of the coding region of the N-gene of Rabies virus (RABV) isolated in canids from Northeastern Brazil. The genetic tree generated using the sequence data described here divided the cluster BRAZILAN CANIDS into two subclusters (DOG-RELATED STRAINS and WILD CANID-RELATED STRAINS) with identities greater than those already described. The two subclusters are sub-divided into geographic groups related to the origin of the isolates, suggesting a long-standing ecological coexistence of the sequence types characteristic of the groups. This article also analyzes the 513-nucleotide stretch of the mitochondrial DNA control region of rabies-positive canids from Northeastern Brazil with a view to identifying the main RABV host among them. Among the four species of wild canids found in the region, two (Cerdocyon thous and Pseudalopex vetulus) are frequently associated with rabies. Phylogenetic analysis of sequence data generated from mtDNA suggests that C. thous is the main wild canid host in the region. The results obtained in this study are in concordance with the zoology and ecology of wild canids, and thus, help improve epidemiologic vigilance of rabies and allow a more targeted control of the disease.

Molecular epidemiology of rabies in Colombia 1994–2005 based on partial nucleoprotein gene sequences

One hundred and twenty-four rabies viruses (RABV) were isolated from humans and eight species of mammals in Colombia during 1994-2005. To determine the genetic and reservoir-associated diversity cDNA fragments encoding 88 amino acids at the carboxyl terminus of the nucleoprotein were sequenced and used in phylogenetic analyses. Eight genetic lineages (GL) were characterized. GL1, GL2 and GL3 consisted of dog-associated antigenic variant (AV) 1 RABV, isolated in the centre-east, north and southwest of Colombia, respectively. GL1 is apparently extinct in Colombia. The GL4 were AV3, AV8 and non-determined (ND) AV viruses associated with hematophagous bats. The GL5 and GL6 consisted of AV4 viruses. GL6 isolate was found associated with Tadarida brasiliensis bats. GL5 segregated independently. The GL7 and GL8 segregated independently within clades associated with colonial insectivorous and solitary bats, respectively. Both of these were represented by NDAV viruses. Viruses isolated from humans grouped within GL2, GL3 and GL4, which in turn corresponded to AV1, 3, 8 and ND. Dogs and D. rotundus are the two major rabies reservoirs and vectors in Colombia. Insectivorous bats may also be important rabies reservoirs but spillovers to other species are rare. Our data were consistent with previous studies in which partial Psi, G and L gene sequences were analyzed. Our results confirmed the existence of RABV of unclassified AV in Colombia.

Molecular epidemiology of rabies virus isolated from different sources during a bat-transmitted human outbreak occurring in Augusto Correa municipality, Brazilian Amazon

We genetically characterize rabies virus (RABV) strains isolated from human cases, domestic and wild animals during a human outbreak of bat-transmitted rabies in Augusto Correa municipality, Pará state, Brazilian Amazon in 2005. Partial nucleotide sequences of the N gene (491 bp) were obtained for all strains, and phylogenetic analysis grouped these into two major clades (Pará and Central-Southeast) and identified them as bat-related viruses genotype I, Desmodus rotundus antigenic variant 3 (AgV3). A molecular clock was used to estimate the time of emergence for each RABV isolate. The molecular data from this study suggest the association of vampire bats with human and domestic animal cases reported in the outbreak, the circulation of at least two predominant lineages in the Pará state, and also a geographic association to lineages dispersion.

Bats as a continuing source of emerging infections in humans

Amongst the 60 viral species reported to be associated with bats, 59 are RNA viruses, which are potentially important in the generation of emerging and re-emerging infections in humans. The prime examples of these are the lyssaviruses and Henipavirus. The transmission of Nipah, Hendra and perhaps SARS coronavirus and Ebola virus to humans may involve intermediate amplification hosts such as pigs, horses, civets and primates, respectively. Understanding of the natural reservoir or introductory host, the amplifying host, the epidemic centre and at-risk human populations are crucial in the control of emerging zoonosis. The association between the bat coronaviruses and certain lyssaviruses with particular bat species implies co-evolution between specific viruses and bat hosts. Cross-infection between the huge number of bat species may generate new viruses which are able to jump the trans-mammalian species barrier more efficiently. The currently known viruses that have been found in bats are reviewed and the risks of transmission to humans are highlighted. Certain families of bats including the Pteropodidae, Molossidae, Phyllostomidae, and Vespertilionidae are most frequently associated with known human pathogens. A systematic survey of bats is warranted to better understand the ecology of these viruses.

Phylogenetic Characterization of Rabies Virus Isolates from Carnivora in Brazil

The incidence of canine rabies has been widely reported in Brazil, and new rabies virus (RV) variants, genetically similar to canine RV, have recently been isolated from foxes. In order to derive the epidemiological characteristics of Brazilian Carnivora RV, Brazilian RVs isolated from dogs, cats, and foxes were genetically analyzed. Brazilian Carnivora RV isolates were divided into 2 main lineages. The predominant lineage was found in dogs and cats, which included the Argentinean and Bolivian Carnivora RV isolates, and was extensively distributed throughout Brazil and surrounding countries. The other lineage consisted of three sublineages containing Brazilian dog and fox RV isolates, with the dog sublineages located on an internal branch of 2 fox sublineages, suggesting that RV transmission events might have occurred between foxes and dogs in the past. These results suggest that contact between dogs and wildlife has the potential to generate new rabies variants and that it is important to control RV infection cycles in both dogs and wildlife to prevent spread of rabies infection.

Molecular epidemiology of rabies virus strains isolated from wild canids in Northeastern Brazil

Rabies in wild canids in Northeastern Brazil is frequent and has been reported for some time, with episodes of rabies transmission from these animals to humans also reported. In this study, we analyzed the antigenic and genetic profiles of the rabies virus nucleoprotein gene, isolated from 20 samples taken from domestic animals and wild canids located in the Northeastern region of Brazil. All viruses isolated from domestic animals (dogs and cats) belonged to the antigenic variant 2 (AgV2). Among the wild animal samples, only four were AgV2, and nine showed a divergent antigenic profile. Phylogenetic analysis revealed two Brazilian clusters. Cluster 1 (Brazilian domestic carnivore-related strains) showed two subclusters, called 1A and 1B, and cluster 2 (Brazilian wild canid-related strains) also showed two subclusters, called 2A and 2B. The majority of the samples with divergent antigenic strains segregated into subcluster 2A. The intracluster identity of cluster 1 was 95.6% and that of cluster 2, 92.4%. When clusters 1 and 2 were compared, an identity of 88.6% was found. The genetic analysis of wild canid samples performed in this study indicates that there are two distinct rabies cycles among canids in Brazil, one represented by domestic canids and the other by wild canids. This study shows that the virus samples isolated in Northeastern Brazil are region and species-specific.

Bat-transmitted human rabies outbreaks, Brazilian Amazon

We describe 2 bat-transmitted outbreaks in remote, rural areas of Portel and Viseu Municipalities, Pará State, northern Brazil. Central nervous system specimens were taken after patients' deaths and underwent immunofluorescent assay and histopathologic examination for rabies antigens; also, specimens were injected intracerebrally into suckling mice in an attempt to isolate the virus. Strains obtained were antigenically and genetically characterized. Twenty-one persons died due to paralytic rabies in the 2 municipalities. Ten rabies virus strains were isolated from human specimens; 2 other cases were diagnosed by histopathologic examination. Isolates were antigenically characterized as Desmodus rotundus variant 3 (AgV3). DNA sequencing of 6 strains showed that they were genetically close to D. rotundus-related strains isolated in Brazil. The genetic results were similar to those obtained by using monoclonal antibodies and support the conclusion that the isolates studied belong to the same rabies cycle, the virus variants found in the vampire bat D. rotundus.

Molecular diversity of rabies viruses associated with bats in Mexico and other countries of the Americas

Bat rabies and its transmission to humans and other species in Mexico were investigated. Eighty-nine samples obtained from rabid livestock, cats, dogs, and humans in Mexico were studied by antigenic typing and partial sequence analysis. Samples were further compared with enzootic rabies associated with different species of bats in the Americas. Patterns of nucleotide variation allowed the definition of at least 20 monophyletic clusters associated with 9 or more different bat species. Several lineages associated with distinctive antigenic patterns were found in rabies viruses related to rabies in vampire bats in Mexico. Vampire bat rabies virus lineages associated with antigenic variant 3 are widely spread from Mexico to South America, suggesting these lineages as the most likely ancestors of vampire bat rabies and the ones that have been moved by vampire bat populations throughout the Americas. Rabies viruses related to Lasiurus cinereus, Histiotus montanus, and some other not yet identified species of the genus Lasiurus were found circulating in Mexico. Long-range dissemination patterns of rabies are not necessarily associated with migratory bat species, as in the case of rabies in Desmodus rotundus and Histiotus montanus. Human rabies was associated with vampire bat transmission in most cases, and in one case, rabies transmission from free-tailed bats was inferred. The occurrence of rabies spillover from bats to domestic animals was also demonstrated. Genetic typing of rabies viruses allowed us to distinguish trends of disease dissemination and to address, in a preliminary fashion, aspects of the complex evolution of rabies viruses in different host-reservoir species.

Molecular epidemiology of rabies from Maranhão and surrounding states in the northeastern region of Brazil

Although many outbreaks of rabies have been reported in northern Brazil, few epidemiological studies of these outbreaks have been undertaken. In this study, molecular epidemiological analyses were performed using 41 rabies virus samples isolated in the Maranhão (MA), Pará (PA), and Tocantins (TO) states of northeastern Brazil. A 599-bp region of the glycoprotein (G) gene was first amplified from each sample by RT-PCR, then sequenced and subjected to phylogenetic analysis. A phylogenetic tree divided the 41 isolates into two clades: Clade I was associated with terrestrial carnivores and Clade II was associated with vampire bats. The Clade I isolates were further sub-divided into two groups. The first group was closer to carnivore isolates that predominate in central Brazil, whereas the second group more closely resembled wild fox isolates from the northeastern coastal state of Paraíba (PB). MA isolates of Clade II formed an entirely separate group. These results demonstrate that bat- and dog-transmitted rabies occur in northwestern Brazil.

Digoxigenin-labeled probe for rabies virus nucleoprotein gene detection

A digoxigenin-labeled probe was produced from the Pasteur virus strain for the detection of the rabies virus N gene. The probe hybridization was performed from amplified N gene obtained by reverse transcription polymerase chain reaction and the results by RT-PCR and hybridization showed 100% agreement. The hybridization, when carried out in products amplified by RT-PCR, increases the sensitivity of this technique even more and confers specificity to the diagnosis. The technique described in this work will be useful in rabies diagnosis laboratories, once the cost is compatible with traditional rabies diagnostic techniques.

Antigenic and genetic characterization of rabies viruses isolated from domestic and wild animals of Brazil identifies the hoary fox as a rabies reservoir

Fifty Brazilian rabies viruses, collected from many different animal species and several regions of the country, were characterized by partial sequencing of the central, variable region of the P gene, a locus useful for sensitive molecular epidemiological studies. Phylogenetic analysis of the sequences, which included comparison with other rabies strains recovered from throughout the Americas, identified three main groups of Brazilian viruses, arbitrarily designated BRL-1 to BRL-3. BRL-1 was found in terrestrial carnivores and clusters with other American strains of the cosmopolitan lineage. BRL-2 comprised two distinct isolates, recovered from two species of non-haematophagous bats, that had evolutionary links to insectivorous-bat-derived strains of North America. BRL-3 consisted of isolates from vampire bats and from livestock species probably infected via contact with vampire bats. The terrestrial group was further subdivided into three subtypes: BRL-1a was associated exclusively with dogs and cats, while BRL-1b and BRL-1c were found exclusively in hoary foxes. These observations strongly support the role of the Brazilian hoary fox as a rabies reservoir. Screening of representative Brazilian rabies viruses against a collection of anti-rabies monoclonal antibodies (mAbs) identified a small panel of mAbs that could be used to discriminate between all Brazilian subgroups as defined by genetic classification in this study.

Geographical Distribution of Vampire Bat-related Cattle Rabies in Brazil

Seventy-seven rabies virus (RV) isolates originating from Brazilian cattle were genetically characterized. Partial nucleoprotein gene sequences of these isolates were phylogenetically and geographically analyzed. Cattle isolates, which clustered with the vampire bat-related RV group, were further subdivided into nine genetic subgroups. These subgroups were distributed widely in lowland regions, with some subgroups separated from each other by mountain ranges. In addition, separation of the groups in mountainous regions was correlated with altitude. These results indicate that cattle rabies is derived from several regionally-defined variants, which suggests that its geographical distribution is related to that of the vampire bat population.