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.
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.
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.
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.
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.
Bat rabies is an emerging disease of public health significance in the Americas. The Caribbean island of Trinidad experiences periodic outbreaks within the livestock population. We performed molecular characterisation of Trinidad rabies virus (RABV) and used a Bayesian phylogeographic approach to investigate the extent to which outbreaks are a result of in situ evolution versus importation of virus from the nearby South American mainland. Trinidadian RABV sequences were confirmed as bat variant and clustered with Desmodus rotundus (vampire bat) related sequences. They fell into two largely temporally defined lineages designated Trinidad I and II. The Trinidad I lineage which included sequences from 1997–2000 (all but two of which were from the northeast of the island) was most closely related to RABV from Ecuador (2005, 2007), French Guiana (1990) and Venezuela (1993, 1994). Trinidad II comprised sequences from the southwest of the island, which clustered into two groups: Trinidad IIa, which included one sequence each from 2000 and 2007, and Trinidad IIb including all 2010 sequences. The Trinidad II sequences were most closely related to sequences from Brazil (1999, 2004) and Uruguay (2007, 2008). Phylogeographic analyses support three separate RABV introductions from the mainland from which each of the three Trinidadian lineages arose. The estimated dates for the introductions and subsequent lineage expansions suggest periods of in situ evolution within Trinidad following each introduction. These data also indicate co-circulation of Trinidad lineage I and IIa during 2000. In light of these findings and the likely vampire bat origin of Trinidadian RABV, further studies should be conducted to investigate the relationship between RABV spatiotemporal dynamics and vampire bat population ecology, in particular any movement between the mainland and Trinidad.
The Caribbean island of Trinidad experiences periodic rabies virus (RABV) outbreaks within the livestock population. In this study, we inferred the evolutionary history of RABV in the Americas and reconstructed past patterns of RABV geographic spread in order to address the question of whether Trinidadian outbreaks arise from locally maintained RABV or are the result of virus importation from the mainland (presumably via infected bats). Our results provide statistical support for three importation events that gave rise to each of three Trinidadian vampire bat-associated lineages identified in the study. They also indicate limited periods of in situ evolution within Trinidad following each of these introductions. The results also support Mexico and Brazil as major epicenters for the expansion of RABV associated with vampire bats throughout the Americas and consequently to Trinidad. The findings of our study are particularly relevant to local RABV monitoring and control. In addition to justifying vampire bats as the main target for active rabies surveillance and control activities in Trinidad, they suggest that more intense surveillance of regions that lie close to the mainland may be warranted. Finally, in light of these findings, further studies should be conducted to investigate the relationship between RABV spatiotemporal dynamics and vampire bat population ecology.
Rabies in bats is considered enzootic throughout the New World, but few comparative data are available for most countries in the region. As part of a larger pathogen detection program, enhanced bat rabies surveillance was conducted in Guatemala, between 2009 and 2011. A total of 672 bats of 31 species were sampled and tested for rabies. The prevalence of rabies virus (RABV) detection among all collected bats was low (0.3%). Viral antigens were detected and infectious virus was isolated from the brains of two common vampire bats (Desmodus rotundus). RABV was also isolated from oral swabs, lungs and kidneys of both bats, whereas viral RNA was detected in all of the tissues examined by hemi-nested RT-PCR except for the liver of one bat. Sequencing of the nucleoprotein gene showed that both viruses were 100% identical, whereas sequencing of the glycoprotein gene revealed one non-synonymous substitution (302T,S). The two vampire bat RABV isolates in this study were phylogenetically related to viruses associated with vampire bats in the eastern states of Mexico and El Salvador. Additionally, 7% of sera collected from 398 bats demonstrated RABV neutralizing antibody. The proportion of seropositive bats varied significantly across trophic guilds, suggestive of complex intraspecific compartmentalization of RABV perpetuation.
In this study we provide results of the first active and extensive surveillance effort for rabies virus (RABV) circulation among bats in Guatemala. The survey included multiple geographic areas and multiple species of bats, to assess the broader public and veterinary health risks associated with rabies in bats in Guatemala. RABV was isolated from vampire bats (Desmodus rotundus) collected in two different locations in Guatemala. Sequencing of the isolates revealed a closer relationship to Mexican and Central American vampire bat isolates than to South American isolates. The detection of RABV neutralizing antibodies in 11 species, including insectivorous, frugivorous, and sanguivorous bats, demonstrates viral circulation in both hematophagous and non-hematophagous bat species in Guatemala. The presence of bat RABV in rural communities requires new strategies for public health education regarding contact with bats, improved laboratory-based surveillance of animals associated with human exposures, and novel techniques for modern rabies prevention and control. Additionally, healthcare practitioners should emphasize the collection of a detailed medical history, including questions regarding bat exposure, for patients presenting with clinical syndromes compatible with rabies or any clinically diagnosed progressive encephalitis.
During the past decade, incidence of human infection with rabies virus (RABV) spread by the common vampire bat (Desmodus rotundus) increased considerably in South America, especially in remote areas of the Amazon rainforest, where these bats commonly feed on humans. To better understand the epizootiology of rabies associated with vampire bats, we used complete sequences of the nucleoprotein gene to infer phylogenetic relationships among 157 RABV isolates collected from humans, domestic animals, and wildlife, including bats, in Peru during 2002–2007. This analysis revealed distinct geographic structuring that indicates that RABVs spread gradually and involve different vampire bat subpopulations with different transmission cycles. Three putative new RABV lineages were found in 3 non–vampire bat species that may represent new virus reservoirs. Detection of novel RABV variants and accurate identification of reservoir hosts are critically important for the prevention and control of potential virus transmission, especially to humans.
rabies; molecular epidemiology; bats; Peru; viruses; zoonoses; vampire bats
Rabies is a fatal infection of the central nervous system primarily transmitted by rabid animal bites. Rabies virus (RABV) circulates through two different epidemiological cycles: terrestrial and aerial, where dogs, foxes or skunks and bats, respectively, act as the most relevant reservoirs and/or vectors. It is widely accepted that insectivorous bats are not important vectors of RABV in Argentina despite the great diversity of bat species and the extensive Argentinean territory.
We studied the positivity rate of RABV detection in different areas of the country, and the antigenic and genetic diversity of 99 rabies virus (RABV) strains obtained from 14 species of insectivorous bats collected in Argentina between 1991 and 2008.
Based on the analysis of bats received for RABV analysis by the National Rabies system of surveillance, the positivity rate of RABV in insectivorous bats ranged from 3.1 to 5.4%, depending on the geographic location. The findings were distributed among an extensive area of the Argentinean territory. The 99 strains of insectivorous bat-related sequences were divided into six distinct lineages associated with Tadarida brasiliensis, Myotis spp, Eptesicus spp, Histiotus montanus, Lasiurus blosseviilli and Lasiurus cinereus. Comparison with RABV sequences obtained from insectivorous bats of the Americas revealed co-circulation of similar genetic variants in several countries. Finally, inter-species transmission, mostly related with Lasiurus species, was demonstrated in 11.8% of the samples.
This study demonstrates the presence of several independent enzootics of rabies in insectivorous bats of Argentina. This information is relevant to identify potential areas at risk for human and animal infection.
In Argentina, successful vaccination and control of terrestrial rabies in the 1980s revealed the importance of the aerial route in RABV transmission. Current distribution of cases shows a predominance of rabies by hematophagous bats in the Northern regions where rabies is a major public health concern; in contrast, in Central and Southern regions where rabies is not a major public health concern, little surveillance is performed. Based on the analysis of insectivorous bats received for RABV analysis by the National Rabies system of surveillance, the positivity rate of RABV in insectivorous bats in these regions ranged from 3.1 to 5.4%. This rate is comparable to other nations such as the United States (9–10%) where insectivorous bats are an important cause of concern for RABV surveillance systems. Antigenic and genetic analysis of a wide collection of rabies strains shows the presence of multiple endemic cycles associated with six bat insectivorous species distributed among an extensive area of the Argentinean territory and several countries of the Americas. Finally, inter-species transmission, mostly related with Lasiurus species, was demonstrated in 11.8% of the samples. Increased public education about the relationship between insectivorous bats and rabies are essential to avoid human cases and potential spread to terrestrial mammals.
Rabies was known to humans as a disease thousands of years ago. In America, insectivorous bats are natural reservoirs of rabies virus. The bat species Tadarida brasiliensis and Lasiurus cinereus, with their respective, host-specific rabies virus variants AgV4 and AgV6, are the principal rabies reservoirs in Chile. However, little is known about the roles of bat species in the ecology and geographic distribution of the virus. This contribution aims to address a series of questions regarding the ecology of rabies transmission in Chile. Analyzing records from 1985–2011 at the Instituto de Salud Pública de Chile (ISP) and using ecological niche modeling, we address these questions to help in understanding rabies-bat ecological dynamics in South America. We found ecological niche identity between both hosts and both viral variants, indicating that niches of all actors in the system are undifferentiated, although the viruses do not necessarily occupy the full geographic distributions of their hosts. Bat species and rabies viruses share similar niches, and our models had significant predictive power even across unsampled regions; results thus suggest that outbreaks may occur under consistent, stable, and predictable circumstances.
The situation of rabies in America has been changing: rabies in dogs has decreased considerably, but bats are increasingly documented as natural reservoirs of other rabies variants. A significant gap exists in understanding of bat-borne rabies in Latin America. We identified bat species known to be connected with enzootic rabies with different antigenic variants in Chile, and compiled large-scale data sets by which to test for ecological niche differences among virus lineages and bat hosts. Our results begin to characterize important ecological factors affecting rabies distribution; modeling rabies in Chile allows comparisons across different latitudes and diverse landscapes. We found that rabies virus strains are found in similar environments, regardless of the bat host involved. This research improves understanding of bat-borne rabies dynamics, and important step towards preventing and controlling this and other emergent diseases linked to bats.
Despite extensive culling of common vampire bats in Latin America, lethal human rabies outbreaks transmitted by this species are increasingly recognized, and livestock rabies occurs with striking frequency. To identify the individual and population-level factors driving rabies virus (RV) transmission in vampire bats, we conducted a longitudinal capture–recapture study in 20 vampire bat colonies spanning four regions of Peru. Serology demonstrated the circulation of RV in vampire bats from all regions in all years. Seroprevalence ranged from 3 to 28 per cent and was highest in juvenile and sub-adult bats. RV exposure was independent of bat colony size, consistent with an absence of population density thresholds for viral invasion and extinction. Culling campaigns implemented during our study failed to reduce seroprevalence and were perhaps counterproductive for disease control owing to the targeted removal of adults, but potentially greater importance of juvenile and sub-adult bats for transmission. These findings provide new insights into the mechanisms of RV maintenance in vampire bats and highlight the need for ecologically informed approaches to rabies prevention in Latin America.
culling; disease thresholds; longitudinal; Lyssavirus; chiroptera; Desmodus
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.
human rabies virus, bat transmission, antigenic and genetic characterization; Brazilian Amazon
Rabies is a fatal encephalitis caused by rabies virus, of the genus Lyssavirus. The principal reservoir for rabies in Latin America is the common vampire bat (Desmodus rotundus), which feeds routinely on the blood of cattle, and when livestock are scarce, may prey on other mammals, including humans. Although rabies is endemic in common vampire bat populations in Guatemala, there is limited research on the extent of exposure to bats among human populations living near bat refuges.
A random sample of 270 of 473 households (57%) in two communities located within 2 Km of a known bat roost was selected and one adult from each household was interviewed. Exposure to bats (bites, scratches or bare skin contact) was reported by 96 (6%) of the 1,721 residents among the selected households. Of those exposed, 40% received rabies post-exposure prophylaxis. Four percent of household respondents reported that they would seek rabies post exposure prophylaxis if they were bitten by a bat.
These findings demonstrate that exposure to bats in communities near bat roosts is common but recognition of the potential for rabies transmission from bats is low. There is a need for educational outreach to raise awareness of bat-associated rabies, prevent exposures to bats and ensure appropriate health-seeking behaviours for bat-inflicted wounds, particularly among communities living near bat roosts in Guatemala.
Rabies; Bat bite; Health practices; Post-exposure prophylaxis; Guatemala; Rabies prevention; Vampire bat
The situation of rabies in America is complex: rabies in dogs has
decreased dramatically, but bats are increasingly recognized as natural reservoirs of
other rabies variants. Here, bat species known to be rabies-positive with different
antigenic variants, are summarized in relation to bat conservation status across
Latin America. Rabies virus is widespread in Latin American bat species, 22.5%75 of bat species have been confirmed as rabies-positive. Most bat species found
rabies positive are classified by the International Union for Conservation of Nature
as “Least Concern”. According to diet type, insectivorous bats had the most species
known as rabies reservoirs, while in proportion hematophagous bats were the most
important. Research at coarse spatial scales must strive to understand rabies
ecology; basic information on distribution and population dynamics of many Latin
American and Caribbean bat species is needed; and detailed information on effects of
landscape change in driving bat-borne rabies outbreaks remains unassessed. Finally,
integrated approaches including public health, ecology, and conservation biology are
needed to understand and prevent emergent diseases in bats.
Rabies virus; Bats; Geographic distribution; Biodiversity
Rabies is a highly fatal non-suppurative encephalomyelitis, caused by the Rabies virus. Dogs are the major reservoir of rabies in India and are the source of infection to other domestic animals. In this report, laboratory investigation and molecular characterization of isolates from two cows with paralytic rabies is described. Necropsy brain samples from the two cows were tested for the presence of rabies antigen using a fluorescent antibody test and the results were confirmed using RT-PCR. Rabies virus was successfully isolated from both the brain samples in a murine neuroblastoma cell line. The phylogenetic analysis of partial nucleoprotein gene sequences of these isolates showed them to be of a variant of Rabies virus which is closely related to the Sri Lankan Rabies virus lineage as previously reported. In addition, partial nucleoprotein genes of 19 more Rabies virus isolates from southern India were sequenced and of these 11 isolates were found to be closely related to the Sri Lankan lineage. The deduced amino acid sequences of the partial nucleoprotein of the Indian isolates were 96–99% identical to the Sri Lankan isolates. This investigation re-confirms the previous speculations that the Sri Lankan variant of the virus may still be actively transmitted by animals in India.
Rabies; India; Sri Lankan variant
Control of rabies requires a consistent supply of dependable resources, constructive cooperation between veterinary and public health authorities, and systematic surveillance. These are challenging in any circumstances, but particularly during conflict. Here we describe available human rabies surveillance data from Iraq, results of renewed sampling for rabies in animals, and the first genetic characterisation of circulating rabies strains from Iraq. Human rabies is notifiable, with reported cases increasing since 2003, and a marked increase in Baghdad between 2009 and 2010. These changes coincide with increasing numbers of reported dog bites. There is no laboratory confirmation of disease or virus characterisation and no systematic surveillance for rabies in animals. To address these issues, brain samples were collected from domestic animals in the greater Baghdad region and tested for rabies. Three of 40 brain samples were positive using the fluorescent antibody test and hemi-nested RT-PCR for rabies virus (RABV). Bayesian phylogenetic analysis using partial nucleoprotein gene sequences derived from the samples demonstrated the viruses belong to a single virus variant and share a common ancestor with viruses from neighbouring countries, 22 (95% HPD 14–32) years ago. These include countries lying to the west, north and east of Iraq, some of which also have other virus variants circulating concurrently. These results suggest possible multiple introductions of rabies into the Middle East, and regular trans-boundary movement of disease. Although 4000 years have passed since the original description of disease consistent with rabies, animals and humans are still dying of this preventable and neglected zoonosis.
Control of rabies requires cooperation between government departments, consistent funding, and an understanding of the epidemiology of the disease obtained through surveillance. Here we describe human rabies surveillance data from Iraq and the results of renewed sampling for rabies in animals. In Iraq, it is obligatory by law to report cases of human rabies. These reports were collated and analysed. Reported cases have increased since 2003, with a marked increase in Baghdad 2009–2010. There is no system for detecting rabies in animals and the strains circulating in Iraq have not previously been characterized. To address this, samples were collected from domestic animals in Baghdad and tested for rabies. Three out of 40 were positive for rabies virus. Comparison of part of the viral genetic sequence with other viruses from the region demonstrated that the viruses from Iraq are more closely related to each other than those from surrounding countries, but diverged from viruses isolated in neighbouring countries approximately 22 (95% HPD 14–32) years ago. Although 4000 years have passed since the original description of disease consistent with rabies, animals and humans are still dying of this preventable and neglected zoonosis.
In nature, rabies virus (RABV; genus Lyssavirus, family Rhabdoviridae) represents an assemblage of phylogenetic lineages, associated with specific mammalian host species. Although it is generally accepted that RABV evolved originally in bats and further shifted to carnivores, mechanisms of such host shifts are poorly understood, and examples are rarely present in surveillance data. Outbreaks in carnivores caused by a RABV variant, associated with big brown bats, occurred repeatedly during 2001–2009 in the Flagstaff area of Arizona. After each outbreak, extensive control campaigns were undertaken, with no reports of further rabies cases in carnivores for the next several years. However, questions remained whether all outbreaks were caused by a single introduction and further perpetuation of bat RABV in carnivore populations, or each outbreak was caused by an independent introduction of a bat virus. Another question of concern was related to adaptive changes in the RABV genome associated with host shifts. To address these questions, we sequenced and analyzed 66 complete and 20 nearly complete RABV genomes, including those from the Flagstaff area and other similar outbreaks in carnivores, caused by bat RABVs, and representatives of the major RABV lineages circulating in North America and worldwide. Phylogenetic analysis demonstrated that each Flagstaff outbreak was caused by an independent introduction of bat RABV into populations of carnivores. Positive selection analysis confirmed the absence of post-shift changes in RABV genes. In contrast, convergent evolution analysis demonstrated several amino acids in the N, P, G and L proteins, which might be significant for pre-adaptation of bat viruses to cause effective infection in carnivores. The substitution S/T242 in the viral glycoprotein is of particular merit, as a similar substitution was suggested for pathogenicity of Nishigahara RABV strain. Roles of the amino acid changes, detected in our study, require additional investigations, using reverse genetics and other approaches.
Host shifts of the rabies virus (RABV) from bats to carnivores are important for our understanding of viral evolution and emergence, and have significant public health implications, particularly for the areas where “terrestrial” rabies has been eliminated. In this study we addressed several rabies outbreaks in carnivores that occurred in the Flagstaff area of Arizona during 2001–2009, and caused by the RABV variant associated with big brown bats (Eptesicus fuscus). Based on phylogenetic analysis we demonstrated that each outbreak resulted from a separate introduction of bat RABV into populations of carnivores. No post-shift changes in viral genomes were detected under the positive selection analysis. Trying to answer the question why certain bat RABV variants are capable for host shifts to carnivores and other variants are not, we developed a convergent evolution analysis, and implemented it for multiple RABV lineages circulating worldwide. This analysis identified several amino acids in RABV proteins which may facilitate host shifts from bats to carnivores. Precise roles of these amino acids require additional investigations, using reverse genetics and animal experimentation. In general, our approach and the results obtained can be used for prediction of host shifts and emergence of other zoonotic pathogens.
Extensive surveillance in bat populations in response to recent emerging diseases has revealed that this group of mammals acts as a reservoir for a large range of viruses. However, the oldest known association between a zoonotic virus and a bat is that between rabies virus and the vampire bat. Vampire bats are only found in Latin America and their unique method of obtaining nutrition, blood-feeding or haematophagy, has only evolved in the New World. The adaptations that enable blood-feeding also make the vampire bat highly effective at transmitting rabies virus. Whether the virus was present in pre-Columbian America or was introduced is much disputed, however, the introduction of Old World livestock and associated landscape modification, which continues to the present day, has enabled vampire bat populations to increase. This in turn has provided the conditions for rabies re-emergence to threaten both livestock and human populations as vampire bats target large mammals. This review considers the ecology of the vampire bat that make it such an efficient vector for rabies, the current status of vampire-transmitted rabies and the future prospects for spread by this virus and its control.
vampire bat; Desmodus rotundus; rabies virus; transmission
Vampire bat related rabies harms both livestock industry and public health sector in central Brazil. The geographical distributions of vampire bat-transmitted rabies virus variants are delimited by mountain chains. These findings were elucidated by analyzing a high conserved nucleoprotein gene. This study aims to elucidate the detailed epidemiological characters of vampire bat-transmitted rabies virus by phylogenetic methods based on 619-nt sequence including unconserved G-L intergenic region.
The vampire bat-transmitted rabies virus isolates divided into 8 phylogenetic lineages in the previous nucleoprotein gene analysis were divided into 10 phylogenetic lineages with significant bootstrap values. The distributions of most variants were reconfirmed to be delimited by mountain chains. Furthermore, variants in undulating areas have narrow distributions and are apparently separated by mountain ridges.
This study demonstrates that the 619-nt sequence including G-L intergenic region is more useful for a state-level phylogenetic analysis of rabies virus than the partial nucleoprotein gene, and simultaneously that the distribution of vampire bat-transmitted RABV variants tends to be separated not only by mountain chains but also by mountain ridges, thus suggesting that the diversity of vampire bat-transmitted RABV variants was delimited by geographical undulations.
Two human rabies cases caused by a bat-associated virus variant were identified in September 2001 in Costa Rica, after a 31-year absence of the disease in persons. Both patients lived in a rural area where cattle had a high risk for bat bites, but neither person had a definitive history of being bitten by a rabid animal. Characterization of the rabies viruses from the patients showed that the reservoir was the hematophagous Vampire Bat, Desmodus rotundus, and that a sick cat was the vector.
human rabies; bat; Costa Rica; dispatch
The nucleoprotein (N) and glycoprotein (G) of 11 Korean rabies virus (RABV) isolates collected from animals diagnosed with rabies between 2008 and 2009 were subjected to molecular and phylogenetic analyses. Six isolates originated from domestic animals (cattle and dogs) and five were obtained from wild free-ranging raccoon dogs. The similarities in the nucleotide sequences of the N gene among all Korean isolates ranged from 98.1 to 99.8%, while those of the G gene ranged from 97.9 to 99.3%. Based on the nucleotide analysis of the N and G genes, the Korean RABV isolates were confirmed as genotype I of Lyssavirus and classified into four distinct subgroups with high similarity. Phylogenetic analysis showed that the Korean isolates were most closely related to the non-Korean NeiMeng1025B and 857r strains, which were isolated from rabid raccoon dogs in Eastern China and Russia, respectively. These findings suggest that the Korean RABV isolates originated from a rabid raccoon dog in Northeastern Asia. Genetic analysis of the Korean RABV isolates revealed no substitutions at several antigenic sites, indicating that the isolates circulating in Korea may be pathogenic in several hosts.
characterization; genotype I; molecular epidemiology; rabies virus
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.
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.
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.
The frequent occurrence of ferret badger-associated human rabies cases in southeast China highlights the lack of laboratory-based surveillance and urges revisiting the potential importance of this animal in rabies transmission. To determine if the ferret badgers actually contribute to human and dog rabies cases, and the possible origin of the ferret badger-associated rabies in the region, an active rabies survey was conducted to determine the frequency of rabies infection and seroprevalence in dogs and ferret badgers.
A retrospective survey on rabies epidemics was performed in Zhejiang, Jiangxi and Anhui provinces in southeast China. The brain tissues from ferret badgers and dogs were assayed by fluorescent antibody test. Rabies virus was isolated and sequenced for phylogenetic analysis. The sera from ferret badgers and dogs were titrated using rabies virus neutralizing antibodies (VNA) test.
The ferret badgers presented a higher percentage of rabies seroconversion than dogs did in the endemic region, reaching a maximum of 95% in the collected samples. Nine ferret badger-associated rabies viruses were isolated, sequenced, and were phylogenetically clustered as a separate group. Nucleotide sequence revealed 99.4-99.8% homology within the ferret badger isolates, and 83-89% homology to the dog isolates in the nucleoprotein and glycoprotein genes in the same rabies endemic regions.
Our data suggest ferret badger-associated rabies has likely formed as an independent enzootic originating from dogs during the long-term rabies infestation in southeast China. The eventual role of FB rabies in public health remains unclear. However, management of ferret badger bites, rabies awareness and control in the related regions should be an immediate need.
In French Guiana, from 1984 to 2011, 14 animal rabies cases and 1 human rabies case (2008) were diagnosed. In January 2011, vampire-bat attacks occurred in 2 isolated villages. In mid-January, a medical team from the Cayenne Centre for Anti-Rabies Treatment visited the sites to manage individuals potentially exposed to rabies and, in April, an anti-rabies vaccination campaign for dogs was conducted. Twenty individuals were bitten by bats in 1 month, most frequently on the feet. The median time to start management was 15 days. The complete Zagreb vaccination protocol (2 doses on day 0 and 1 dose on days 7 and 21) was administered to 16 patients, 12 also received specific immunoglobulins. The antibody titration was obtained for 12 patients (different from those who received immunoglobulins). The antibody titers were ≥0.5 EU/mL for all of them. The serology has not been implemented for the 12 patients who received immunoglobulins. Accidental destruction of a vampire-bat colony could be responsible for the attacks. The isolation and absence of sensitization of the populations were the main explanations for the management difficulties encountered. Sensitization programs should be conducted regularly.
Rabies is a disease almost invariably fatal in humans once the first clinical signs appear. In French Guiana bats represent the virus reservoir, especially vampire bats. From 1984 to 2011, 14 animal rabies cases and 1 human rabies case (2008) were diagnosed. In case of bat bite, anti-rabies immunoglobulins (RIG) and rabies vaccine must be rapidly administrated. The specific rabies management is exclusively performed by Centre for Anti-Rabies Treatment (CART), located at the Institut Pasteur in Cayenne, the prefecture of French Guiana, and 6 Anti-Rabies Treatment Outposts distributed along the coastal edge and along the two main rivers. Only a CART physician can administer RIG. In January 2011, vampire-bat attacks occurred in 2 isolated villages. In mid-January, a medical team from the CART visited the sites to manage individuals potentially exposed to rabies and, in April, an anti-rabies vaccination campaign for dogs was conducted. The most relevant contribution of this study is to underline difficulties to provide rabies post-exposure prophylaxis to remote populations exposed to bat rabies in the Amazonian region and to show the lack of awareness of these rural populations concerning rabies and the risk associated to vampire bats.
To identify the presence of genetic clusters of rabies virus at the territory of Ukraine and to determine the degree of activity of rabies vaccines against these genetic clusters.
To develop and implement an effective program of rabies eradication in Ukraine in 2008 was founded the unique collection of samples of pathological materials confirmed as positive in rabies at the regional veterinary laboratories of Ukraine. The collection is constantly updated and to present moment it includes 1389 samples from all regions of Ukraine, selected from 17 animal species and humans.
Identification of the rabies virus in samples of pathological material for their further selection was carried out using the test developed by us which based on RT-PCR with primers complementary to the conservative fragments of the 5’-end of nucleoprotein gene of rabies virus.
For the study of the street rabies virus isolates from the collection we use RT-PCR with the primers pair (509, 304) flanking the variable 3’-end part of nucleoprotein gene of the reference strain of rabies virus CVS (fragment in 377 bp).
Studies of rabies vaccines activity were carried out with modified method of U.S. National Institutes of Health using rabies virus street isolates of both genetic clusters instead of the Challenge Virus Standard (CVS). All isolates of street rabies virus were inoculated in a dose of 5–50 LD50. The criteria for evaluation of protective activity of rabies vaccine was effective dose (− lg ED50).
In molecular genetic studies with variant-specific primers we established the presence in Ukraine of two clusters of rabies virus. Clusters I circulates on the right bank of the Dnipro river (the largest water barrier that divides the country into eastern and western side), and cluster II – on the left bank of the Dnieper.
The relationship of these variants with the epizootic situation was researched. For this purpose epizootological zoning of Ukraine according to the intensity of the epizootic situation in 2005–2009 was carried out. As a result of this analysis all the regions of Ukraine belong to three categories: high, medium and low epizootic situation intensity of rabies.
The projection of differentiated genetic clusters on the epizootic situation showed that cluster II circulating at Left Bank of the Dnieper in areas with high and medium intensity of the epizootic situation, and the cluster I – at the Right Bank of the Dnieper, mainly in the areas with low intensity of the epizootic situation.
That’s why our interest was in the degree of protection of rabies vaccines against street rabies virus isolates belonging to these two genetic clusters.
The commercial vaccines made with rabies virus vaccine strains SAD (Street-Alabama-Dufferin) and Wistar PM/WI were chosen to evaluate this parameter.
After the mathematical calculations of effective dose and the analysis of the data the less effective protection of rabies vaccines (at 29–30 %) against street rabies virus isolates belonging to cluster II in comparison with isolates belonging to cluster I irrespective to the strain vaccine is made was shown.
The data will be used for the effective planning of specific prophylaxis of rabies in Ukraine based on differentiated approach to distribution of rabies vaccines in according to region and their activity.
rabies vaccine; vaccine activity; street rabies virus isolates; genetic variants of rabies virus
The majority of rabies virus (RV) infections are caused by bites or scratches from rabid carnivores or bats. Usually, RV utilizes the retrograde transport within the neuronal network to spread from the infection site to the central nervous system (CNS) where it replicates in neuronal somata and infects other neurons via trans-synaptic spread. We speculate that in addition to the neuronal transport of the virus, hematogenous spread from the site of infection directly to the brain after accidental spill over into the vascular system might represent an alternative way for RV to invade the CNS. So far, it is unknown whether hematogenous spread has any relevance in RV pathogenesis. To determine whether certain RV variants might have the capacity to invade the CNS from the periphery via hematogenous spread, we infected mice either intramuscularly (i.m.) or intravenously (i.v.) with the dog-associated RV DOG4 or the silver-haired bat-associated RV SB. In addition to monitoring the progression of clinical signs of rabies we used immunohistochemistry and quantitative reverse transcription polymerase chain reaction (qRT-PCR) to follow the spread of the virus from the infection site to the brain. In contrast to i.m. infection where both variants caused a lethal encephalopathy, only i.v. infection with SB resulted in the development of a lethal infection. While qRT-PCR did not reveal major differences in virus loads in spinal cord or brain at different times after i.m. or i.v. infection of SB, immunohistochemical analysis showed that only i.v. administered SB directly infected the forebrain. The earliest affected regions were those hypothalamic nuclei, which are connected by neurosecretory fibers to the circumventricular organs neurohypophysis and median eminence. Our data suggest that hematogenous spread of SB can lead to a fatal encephalopathy through direct retrograde invasion of the CNS at the neurovascular interface of the hypothalamus-hypophysis system. This alternative mode of virus spread has implications for the post exposure prophylaxis of rabies, particularly with silver-haired bat-associated RV.
Rabies virus (RV) infects mammalian neurons and cycles in regionally distinct animal populations such as the red fox in Europe, domestic canines in Asia, or raccoons, skunks and bats in Northern America. Although human rabies can be prevented by pre- and post-exposure prophylaxis, more than 50,000 people die annually from the severe encephalopathy caused by RV. Recently, two cases of RV transmission by organ transplantation were reported. In our study, using intravenous inoculation of mice, we evaluated the pathogenetic relevance of virions that reach the bloodstream. Mice inoculated intravenously with a canine-derived RV survived the infection in contrast to intramuscularly injected mice, while mice infected with a silver-haired bat-related RV succumbed to the disease regardless of the route of inoculation. We found that the silver-haired bat-related RV was able to transit from the blood to the brain by invading neurosecretory fibers of the hypothalamus, which form neurohemal synapses lacking a blood-brain-barrier. This newly described route of brain invasion might reflect how RV reached the central nervous system from transplanted organs, since it takes longer to establish the neural connections between host and grafted tissue necessary for classical RV migration than the time until the infection became symptomatic in the two reported cases.
The first human rabies case in Chile since 1972 occurred in March 1996 in a patient without history of known exposure. Antigenic and genetic characterization of the rabies isolate indicated that its reservoir was the insectivorous bat Tadarida brasiliensis. This is the first human rabies case caused by an insectivorous bat rabies virus variant reported in Latin America.
rabies; Chile; bats; human; Latin America; Tadarida
After a human rabies outbreak in southeastern Peru, we collected bats to estimate the prevalence of rabies in various species. Among 165 bats from 6 genera and 10 species, 10.3% were antibody positive; antibody prevalence was similar in vampire and nonvampire bats. Thus, nonvampire bats may also be a source for human rabies in Peru.
Rabies virus; rabies; viruses; outbreak investigation; reservoir; vampire bats; Peru; dispatch