Characterisation of an Australian bat lyssavirus variant isolated from an insectivorous bat

Emergence, Tropism, Disease, and Treatment of Australian Bat Lyssavirus Infections in Humans

Australian bat lyssavirus (ABLV) is a negative-sense, single-stranded RNA rhabdovirus capable of causing fatal acute encephalitis in humans with similar pathogenesis to its closest serologic relative, rabies virus (RABV). In this review, we describe emergence and classification of ABLV, its known virology, reservoirs, and hosts, as well as both the pathogenesis and treatment approaches currently employed for presumed infections. ABLV was first identified in New South Wales, Australia in 1996 and emerged in humans months later in Queensland, Australia. Only five known bat reservoirs, all of which fall within the Pteropus and Saccolaimus genera, have been identified to date. Although ABLV antigens have been identified in bats located outside of Australia, the three known human ABLV infections to date have occurred within Australia. As such, there remains a potential for ABLV to expand its presence within and beyond Australia. ABLV infections are currently treated as if they were RABV infections by administering neutralizing antibodies against RABV at the site of the wound and employing the rabies vaccine upon possible exposures. Due to its recent emergence, there is still much left unknown about ABLV, posing concerns with how to safely and effectively address current and future ABLV infections.

Phylogeographic Aspects of Bat Lyssaviruses in Europe: A Review

During the last few decades, bat lyssaviruses have become the topic of intensive molecular and epidemiological investigations. Since ancient times, rhabdoviruses have caused fatal encephalitis in humans which has led to research into effective strategies for their eradication. Modelling of potential future cross-species virus transmissions forms a substantial component of the recent infection biology of rabies. In this article, we summarise the available data on the phylogeography of both bats and lyssaviruses in Europe and the adjacent reg ions, especially in the contact zone between the Palearctic and Ethiopian realms. Within these zones, three bat families are present with high potential for cross-species transmission and the spread of lyssaviruses in Phylogroup II to Europe (part of the western Palearctic). The lack of effective therapies for rabies viruses in Phylogroup II and the most divergent lyssaviruses generates impetus for additional phylogenetic and virological research within this geographical region.

Emerging Rhabdoviruses and Human Infection

Rhabdoviridae is a large viral family, with members infecting a diverse range of hosts including, vertebrate species, arthropods, and plants. The predominant human pathogen within the family is Rabies lyssavirus, the main cause of human rabies. While rabies is itself a neglected disease, there are other, less well studied, rhabdoviruses known to cause human infection. The increasing application of next-generation sequencing technology to clinical samples has led to the detection of several novel or rarely detected rhabdoviruses associated with febrile illness. Many of these viruses have been detected in low- and middle-income countries where the extent of human infection and the burden of disease remain largely unquantified. This review describes the rhabdoviruses other than Rabies lyssavirus that have been associated with human infection. The discovery of the Bas Congo virus and Ekpoma virus is discussed, as is the re-emergence of species such as Le Dantec virus, which has recently been detected in Africa 40 years after its initial isolation. Chandipura virus and the lyssaviruses that are known to cause human rabies are also described. Given their association with human disease, the viruses described in this review should be prioritised for further study.

Novel Bat Lyssaviruses Identified by Nationwide Passive Surveillance in Taiwan, 2018–2021

Bat lyssaviruses were identified in Taiwan’s bat population during 2016–2017. The lyssavirus surveillance system was continuously conducted to understand the epidemiology. Through this system, the found dead bats were collected for lyssavirus detection by direct fluorescent antibody test and reverse transcription polymerase chain reaction. Three bats were identified as positive during 2018–2021. A novel lyssavirus, designated as Taiwan bat lyssavirus 2, was detected in a Nyctalus plancyi velutinus. This lyssavirus had less than 80% nucleotide identity in the nucleoprotein (N) gene with other lyssavirus species, forming a separate branch in the phylogenetic analysis. The other two cases were identified in Pipistrellus abramus (Japanese pipistrelles); they were identified to be similar to the former lyssavirus identified in 2016–2017, which was renominated as Taiwan bat lyssavirus 1 (TWBLV-1) in this study. Even though one of the TWBLV-1 isolates showed high genetic diversity in the N gene compared with other TWBLV-1 isolates, it may be a TWBLV-1 variant but not a new species based on its high amino acid identities in the nucleoprotein, same host species, and same geographic location as the other TWBLV-1.

Bats and viruses: a death-defying friendship

Bats have a primeval evolutionary origin and have adopted various survival methods. They have played a central role in the emergence of various viral diseases. The sustenance of a plethora of virus species inside them has been an earnest area of study. This review explains how the evolution of viruses in bats has been linked to their metabolic pathways, flight abilities, reproductive abilities and colonization behaviors. The utilization of host immune response by DNA and RNA viruses is a commencement of the understanding of differences in the impact of viral infection in bats from other mammals. Rabies virus and other lyssa viruses have had long documented history as bat viruses. While many others like Ebola virus, Nipah virus, Hantavirus, SARS-CoV, MERS-CoV and other new emerging viruses like Sosuga virus, Menangle and Tioman virus are now being studied extensively for their transmission in new hosts. The ongoing pandemic SARS-CoV-2 virus has also been implicated to be originated from bats. Certain factors have been linked to spillover events while the scope of entitlement of other conditions in the spread of diseases from bats still exists. However, certain physiological and ecological parameters have been linked to specific transmission patterns, and more definite proofs are awaited for establishing these connections.

Phenotypic Divergence of P Proteins of Australian Bat Lyssavirus Lineages Circulating in Microbats and Flying Foxes

Bats are reservoirs of many pathogenic viruses, including the lyssaviruses rabies virus (RABV) and Australian bat lyssavirus (ABLV). Lyssavirus strains are closely associated with particular host reservoir species, with evidence of specific adaptation. Associated phenotypic changes remain poorly understood but are likely to involve phosphoprotein (P protein), a key mediator of the intracellular virus-host interface. Here, we examine the phenotype of P protein of ABLV, which circulates as two defined lineages associated with frugivorous and insectivorous bats, providing the opportunity to compare proteins of viruses adapted to divergent bat species. We report that key functions of P protein in the antagonism of interferon/signal transducers and activators of transcription 1 (STAT1) signaling and the capacity of P protein to undergo nuclear trafficking differ between lineages. Molecular mapping indicates that these differences are functionally distinct and appear to involve modulatory effects on regulatory regions or structural impact rather than changes to defined interaction sequences. This results in partial but significant phenotypic divergence, consistent with "fine-tuning" to host biology, and with potentially distinct properties in the virus-host interface between bat families that represent key zoonotic reservoirs.

Isolation and Characterization of Cross-Reactive Human Monoclonal Antibodies That Potently Neutralize Australian Bat Lyssavirus Variants and Other Phylogroup 1 Lyssaviruses

Australian bat lyssavirus (ABLV) is a rhabdovirus that circulates in four species of pteropid bats (ABLVp) and the yellow-bellied sheath-tailed bat (ABLVs) in mainland Australia. In the three confirmed human cases of ABLV, rabies illness preceded fatality. As with rabies virus (RABV), post-exposure prophylaxis (PEP) for potential ABLV infections consists of wound cleansing, administration of the rabies vaccine and injection of rabies immunoglobulin (RIG) proximal to the wound. Despite the efficacy of PEP, the inaccessibility of human RIG (HRIG) in the developing world and the high immunogenicity of equine RIG (ERIG) has led to consideration of human monoclonal antibodies (hmAbs) as a passive immunization option that offers enhanced safety and specificity. Using a recombinant vesicular stomatitis virus (rVSV) expressing the glycoprotein (G) protein of ABLVs and phage display, we identified two hmAbs, A6 and F11, which completely neutralize ABLVs/ABLVp, and RABV at concentrations ranging from 0.39 and 6.25 µg/mL and 0.19 and 0.39 µg/mL respectively. A6 and F11 recognize overlapping epitopes in the lyssavirus G protein, effectively neutralizing phylogroup 1 lyssaviruses, while having little effect on phylogroup 2 and non-grouped diverse lyssaviruses. These results suggest that A6 and F11 could be effective therapeutic and diagnostic tools for phylogroup 1 lyssavirus infections.

Australian Bat Lyssavirus: Analysis of National Bat Surveillance Data from 2010 to 2016

Australian bat lyssavirus (ABLV) was first described in 1996 and has been regularly detected in Australian bats since that time. While the virus does not cause population level impacts in bats and has minimal impacts on domestic animals, it does pose a public health risk. For this reason, bats are monitored for ABLV and a national dataset is collated and maintained by Wildlife Health Australia. The 2010–2016 dataset was analysed using logistic regression and time-series analysis to identify predictors of infection status in bats and the factors associated with human exposure to bats. In common with previous passive surveillance studies, we found that little red flying-foxes (Pteropus scapulatus) are more likely than other species to be infected with ABLV. In the four Australian mainland species of flying-fox, there are seasonal differences in infection risk that may be associated with reproductive cycles, with summer and autumn the seasons of greatest risk. The risk of human contact was also seasonal, with lower risk in winter. In line with other studies, we found that the circumstances in which the bat is encountered, such as exhibiting abnormal behaviour or being grounded, are risk factors for ABLV infection and human contact and should continue be key components of public health messaging. We also found evidence of biased recording of some types of information, which made interpretation of some findings more challenging. Strengthening of “One Health” linkages between public health and animal health services at the operational level could help overcome these biases in future, and greater harmonisation nationally would increase the value of the dataset.

Viral Diversity of Microbats within the South West Botanical Province of Western Australia

Bats are known reservoirs of a wide variety of viruses that rarely result in overt clinical disease in the bat host. However, anthropogenic influences on the landscape and climate can change species assemblages and interactions, as well as undermine host-resilience. The cumulative result is a disturbance of bat-pathogen dynamics, which facilitate spillover events to sympatric species, and may threaten bat communities already facing synergistic stressors through ecological change. Therefore, characterisation of viral pathogens in bat communities provides important basal information to monitor and predict the emergence of diseases relevant to conservation and public health. This study used targeted molecular techniques, serological assays and next generation sequencing to characterise adenoviruses, coronaviruses and paramyxoviruses from 11 species of insectivorous bats within the South West Botanical Province of Western Australia. Phylogenetic analysis indicated complex ecological interactions including virus-host associations, cross-species infections, and multiple viral strains circulating concurrently within selected bat populations. Additionally, we describe the entire coding sequences for five alphacoronaviruses (representing four putative new species), and one novel adenovirus. Results indicate that viral burden (both prevalence and richness) is not homogeneous among species, with Chalinolobus gouldii identified as a key epidemiological element within the studied communities.

Insights into Australian Bat Lyssavirus in Insectivorous Bats of Western Australia

Australian bat lyssavirus (ABLV) is a known causative agent of neurological disease in bats, humans and horses. It has been isolated from four species of pteropid bats and a single microbat species (Saccolaimus flaviventris). To date, ABLV surveillance has primarily been passive, with active surveillance concentrating on eastern and northern Australian bat populations. As a result, there is scant regional ABLV information for large areas of the country. To better inform the local public health risks associated with human-bat interactions, this study describes the lyssavirus prevalence in microbat communities in the South West Botanical Province of Western Australia. We used targeted real-time PCR assays to detect viral RNA shedding in 839 oral swabs representing 12 species of microbats, which were sampled over two consecutive summers spanning 2016–2018. Additionally, we tested 649 serum samples via Luminex^® assay for reactivity to lyssavirus antigens. Active lyssavirus infection was not detected in any of the samples. Lyssavirus antibodies were detected in 19 individuals across six species, with a crude prevalence of 2.9% (95% CI: 1.8–4.5%) over the two years. In addition, we present the first records of lyssavirus exposure in two Nyctophilus species, and Falsistrellusmackenziei.

Survey of rabies vaccination status of Queensland veterinarians and veterinary students

BACKGROUND

To determine the rabies vaccination status of Queensland veterinarians and veterinary students and their perception of zoonotic risk from Australian bat lyssavirus (ABLV).

DESIGN

Cross-sectional questionnaire surveys.

METHODS

Questionnaires were sent by post in 2011 to veterinary surgeons registered in Queensland, to final-year veterinary students at James Cook University via SurveyMonkey® in 2013 and to final-year veterinary students at James Cook University and University of Queensland via SurveyMonkey® in 2014.

RESULTS

The response rate for registered veterinarians was 33.5% and for veterinary students 33.3% and 30% in 2013 and 2014, respectively. Of the 466 registered veterinary surgeons, 147 (31.5%) had been vaccinated, with 72 (15.5%) currently vaccinated. For veterinary students the rabies vaccination rate was 20.0% (4/20) and 13.0% (6/46) in the 2013 and 2014 surveys, respectively. More than 95% of veterinary students had received the mandatory Q fever vaccine. Both veterinarians and students regarded bats and horses as high-risk species for zoonoses.

CONCLUSIONS

Queensland veterinarians and veterinary students have low levels of protection against ABLV. Although incidents of ABLV spilling over from a bat to a domestic mammal are likely to remain rare, they pose a significant human health and occupational risk given the outcome of infection in humans is high consequence. Principals of veterinary practices and veterinary authorities in Australia should implement a policy of rabies vaccination for clinical staff and veterinary students.

Assessment of a Rabies Virus Rapid Diagnostic Test for the Detection of Australian Bat Lyssavirus

Australian bat lyssavirus (ABLV) is closely related to the classical rabies virus and has been associated with three human fatalities and two equine fatalities in Australia. ABLV infection in humans causes encephalomyelitis, resulting in fatal disease, but has no effective therapy. The virus is maintained in enzootic circulation within fruit bats (Pteropid spp.) and at least one insectivorous bat variety (Saccolaimus flaviventris). Most frequently, laboratory testing is conducted on pteropodid bat brains, either following a potential human exposure through bites, scratches and other direct contacts with bats, or as opportunistic assessment of sick or dead bats. The level of medical intervention and post-exposure prophylaxis is largely determined on laboratory testing for antigen/virus as the demonstrable infection status of the in-contact bat. This study evaluates the comparative diagnostic performance of a lateral flow test, Anigen Rabies Ag detection rapid test (RDT), in pteropodid variant of ABLV-infected bat brain tissues. The RDT demonstrated 100% agreement with the reference standard fluorescent antibody test on 43 clinical samples suggesting a potential application in rapid diagnosis of pteropodid variant of ABLV infection. A weighted Kappa value of 0.95 confirmed a high level of agreement between both tests.

Evidence of Australian bat lyssavirus infection in diverse Australian bat taxa

Historically, Australia was considered free of rabies and rabieslike viruses. Thus, the identification of Australian bat lyssavirus (ABLV) in 1996 in a debilitated bat found by a member of the public precipitated both public health consternation and a revision of lyssavirus taxonomy. Subsequent observational studies sought to elaborate the occurrence and frequency of ABLV infection in Australian bats. This paper describes the taxonomic diversity of bat species showing evidence of ABLV infection to better inform public health considerations. Blood and/or brain samples were collected from two cohorts of bats (wild‐caught and diagnostic submissions) from four Australian states or territories between April 1996 and October 2002. Fresh brain impression smears were tested for ABLV antigen using fluorescein‐labelled anti‐rabies monoclonal globulin (CENTOCOR) in a direct fluorescent antibody test; sera were tested for the presence of neutralising antibodies using a rapid fluorescent focus inhibition test. A total of 3,217 samples from 2,633 bats were collected and screened: brain samples from 1,461 wild‐caught bats and 1,086 submitted bats from at least 16 genera and seven families, and blood samples from 656 wild‐caught bats and 14 submitted bats from 14 genera and seven families. Evidence of ABLV infection was found in five of the six families of bats occurring in Australia, and in three of the four Australian states/territories surveyed, supporting the historic presence of the virus in Australia. While the infection prevalence in the wild‐caught cohort is evidently low, the significantly higher infection prevalence in rescued bats in urban settings represents a clear and present public health significance because of the higher risk of human exposure.

Lyssavirus in Indian Flying Foxes, Sri Lanka

A novel lyssavirus was isolated from brains of Indian flying foxes (Pteropus medius) in Sri Lanka. Phylogenetic analysis of complete virus genome sequences, and geographic location and host species, provides strong evidence that this virus is a putative new lyssavirus species, designated as Gannoruwa bat lyssavirus.

The Global Phylogeography of Lyssaviruses - Challenging the 'Out of Africa' Hypothesis

Rabies virus kills tens of thousands of people globally each year, especially in resource-limited countries. Yet, there are genetically- and antigenically-related lyssaviruses, all capable of causing the disease rabies, circulating globally among bats without causing conspicuous disease outbreaks. The species richness and greater genetic diversity of African lyssaviruses, along with the lack of antibody cross-reactivity among them, has led to the hypothesis that Africa is the origin of lyssaviruses. This hypothesis was tested using a probabilistic phylogeographical approach. The nucleoprotein gene sequences from 153 representatives of 16 lyssavirus species, collected between 1956 and 2015, were used to develop a phylogenetic tree which incorporated relevant geographic and temporal data relating to the viruses. In addition, complete genome sequences from all 16 (putative) species were analysed. The most probable ancestral distribution for the internal nodes was inferred using three different approaches and was confirmed by analysis of complete genomes. These results support a Palearctic origin for lyssaviruses (posterior probability = 0.85), challenging the ‘out of Africa’ hypothesis, and suggest three independent transmission events to the Afrotropical region, representing the three phylogroups that form the three major lyssavirus clades.

Rabies virus kills tens of thousands of people globally each year and causes indescribable misery and family disturbance, especially in developing countries. Yet in much of the world there are related viruses, called lyssaviruses, which circulate among bats without causing conspicuous outbreaks. The greater diversity of African lyssaviruses has led to the hypothesis that Africa is the origin of these viruses. To test this hypothesis, the genetic data from 153 representative viruses from 16 available lyssavirus species from across the world dated between 1956 and 2015 were analysed. Statistical models were used to reconstruct the historical processes that lead to the contemporary distribution of these viruses. Our results support a Palearctic origin for lyssaviruses, not Afrotropic, and suggest three independent transmission events to Africa from the Palearctic region.

The Role of Bats as Reservoir Hosts of Emerging Neuroviruses

Recent studies have clearly shown that bats are the reservoir hosts of a wide diversity of novel viruses with representatives from most of the known animal virus families. In many respects bats make ideal reservoir hosts for viruses: they are the only mammals that fly, thus assisting in virus dispersal; they roost in large numbers, thus aiding transmission cycles; some bats hibernate over winter, thus providing a mechanism for viruses to persist between seasons; and genetic factors may play a role in the ability of bats to host viruses without resulting in clinical disease. Within the broad diversity of viruses found in bats are some important neurological pathogens, including rabies and other lyssaviruses, and Hendra and Nipah viruses, two recently described viruses that have been placed in a new genus, Henipaviruses in the family Paramyxoviridae. In addition, bats can also act as alternative hosts for the flaviviruses Japanese encephalitis and St Louis encephalitis viruses, two important mosquito-borne encephalitogenic viruses, and bats can assist in the dispersal and over-wintering of these viruses. Bats are also the reservoir hosts of progenitors of SARS and MERS coronaviruses, although other animals act as spillover hosts. This chapter presents the physiological and ecological factors affecting the ability of bats to act as reservoirs of neurotropic viruses, and describes the major transmission cycles leading to human infection.

Zoonotic Viruses and Conservation of Bats

Many of the recently emerging highly virulent zoonotic diseases have a likely bat origin, for example Hendra, Nipah, Ebola and diseases caused by coronaviruses. Presumably because of their long history of coevolution, most of these viruses remain subclinical in bats, but have the potential to cause severe illnesses in domestic and wildlife animals and also humans. Spillovers from bats to humans either happen directly (via contact with infected bats) or indirectly (via intermediate hosts such as domestic or wildlife animals, by consuming food items contaminated by saliva, faeces or urine of bats, or via other environmental sources). Increasing numbers of breakouts of zoonotic viral diseases among humans and livestock have mainly been accounted to human encroachment into natural habitat, as well as agricultural intensification, deforestation and bushmeat consumption. Persecution of bats, including the destruction of their roosts and culling of whole colonies, has led not only to declines of protected bat species, but also to an increase in virus prevalence in some of these populations. Educational efforts are needed in order to prevent future spillovers of bat-borne viruses to humans and livestock, and to further protect bats from unnecessary and counterproductive culling.

Australian bat lyssavirus infection in two horses

In May 2013, the first cases of Australian bat lyssavirus infections in domestic animals were identified in Australia. Two horses (filly-H1 and gelding-H2) were infected with the Yellow-bellied sheathtail bat (YBST) variant of Australian bat lyssavirus (ABLV). The horses presented with neurological signs, pyrexia and progressing ataxia. Intra-cytoplasmic inclusion bodies (Negri bodies) were detected in some Purkinje neurons in haematoxylin and eosin (H&E) stained sections from the brain of one of the two infected horses (H2) by histological examination. A morphological diagnosis of sub-acute moderate non-suppurative, predominantly angiocentric, meningo-encephalomyelitis of viral aetiology was made. The presumptive diagnosis of ABLV infection was confirmed by the positive testing of the affected brain tissue from (H2) in a range of laboratory tests including fluorescent antibody test (FAT) and real-time PCR targeting the nucleocapsid (N) gene. Retrospective testing of the oral swab from (H1) in the real-time PCR also returned a positive result. The FAT and immunohistochemistry (IHC) revealed an abundance of ABLV antigen throughout the examined brain sections. ABLV was isolated from the brain (H2) and oral swab/saliva (H1) in the neuroblastoma cell line (MNA). Alignment of the genome sequence revealed a 97.7% identity with the YBST ABLV strain.

Recent observations on Australian bat lyssavirus tropism and viral entry

Australian bat lyssavirus (ABLV) is a recently emerged rhabdovirus of the genus lyssavirus considered endemic in Australian bat populations that causes a neurological disease in people indistinguishable from clinical rabies. There are two distinct variants of ABLV, one that circulates in frugivorous bats (genus Pteropus) and the other in insectivorous microbats (genus Saccolaimus). Three fatal human cases of ABLV infection have been reported, the most recent in 2013, and each manifested as acute encephalitis but with variable incubation periods. Importantly, two equine cases also arose recently in 2013, the first occurrence of ABLV in a species other than bats or humans. Similar to other rhabdoviruses, ABLV infects host cells through receptor-mediated endocytosis and subsequent pH-dependent fusion facilitated by its single fusogenic envelope glycoprotein (G). Recent studies have revealed that proposed rabies virus (RABV) receptors are not sufficient to permit ABLV entry into host cells and that the unknown receptor is broadly conserved among mammalian species. However, despite clear tropism differences between ABLV and RABV, the two viruses appear to utilize similar endocytic entry pathways. The recent human and horse infections highlight the importance of continued Australian public health awareness of this emerging pathogen.

Host cell tropism mediated by Australian bat lyssavirus envelope glycoproteins

Australian bat lyssavirus (ABLV) is a rhabdovirus of the lyssavirus genus capable of causing fatal rabies-like encephalitis in humans. There are two variants of ABLV, one circulating in pteropid fruit bats and another in insectivorous bats. Three fatal human cases of ABLV infection have been reported with the third case in 2013. Importantly, two equine cases also arose in 2013; the first occurrence of ABLV in a species other than bats or humans. We examined the host cell entry of ABLV, characterizing its tropism and exploring its cross-species transmission potential using maxGFP-encoding recombinant vesicular stomatitis viruses that express ABLV G glycoproteins. Results indicate that the ABLV receptor(s) is conserved but not ubiquitous among mammalian cell lines and that the two ABLV variants can utilize alternate receptors for entry. Proposed rabies virus receptors were not sufficient to permit ABLV entry into resistant cells, suggesting that ABLV utilizes an unknown alternative receptor(s).

Molecular characterization of China human rabies vaccine strains

To understand the molecular characteristics of China human rabies vaccine strains, we report the full-length genome of the aG strain and present a comprehensive analysis of this strain and almost all available lyssavirus genomes (58 strains) from GenBank (as of Jan 6, 2011). It is generally considered that the G protein plays a predominant role in determining the pathogenicity of the virus, to this end we predicted the tertiary structure of the G protein of aG strain, CTN181 strain and wild type strain HN10 based on the crystal structure of Vesicular stomatitis virus (VSV) G. The predicted RABV G structure has a similar topology to VSV G and the ectodomain can be divided into 4 distinct domains DI - DIV. By mapping the characterized mutations to this structure between China vaccine strains and their close street strains, we speculate that the G303(P-H) mutations of CTN181 and HN10 causing DII 3D change may be associated with the II attenuated virulence in both strains. Specifically, the two signature mutations (G165P and G231P) in the aG strain are within ßsheets, suggesting that both sites are of structural importance.

Reservoirs and vectors of emerging viruses

Wildlife, especially mammals and birds, are hosts to an enormous number of viruses, most of which we have absolutely no knowledge about even though we know these viruses circulate readily in their specific niches. More often than not, these viruses are silent or asymptomatic in their natural hosts. In some instances, they can infect other species, and in rare cases, this cross-species transmission might lead to human infection. There are also instances where we know the reservoir hosts of zoonotic viruses that can and do infect humans. Studies of these animal hosts, the reservoirs of the viruses, provide us with the knowledge of the types of virus circulating in wildlife species, their incidence, pathogenicity for their host, and in some instances, the potential for transmission to other hosts. This paper describes examples of some of the viruses that have been detected in wildlife, and the reservoir hosts from which they have been detected. It also briefly explores the spread of arthropod-borne viruses and their diseases through the movement and establishment of vectors in new habitats.

Bat Rabies

The lyssaviruses are a diverse group of viruses capable of causing rabies, which is an invariably fatal encephalitic disease in both humans and animals. Currently, the lyssavirus genus consists of 12 species with 11 of these distinct species having been isolated from bats. The basis for the apparent geographical segregation of bat lyssavirus infection between the Old and New World is poorly understood. In the New World species of insectivorous, frugivorous, and hematophagous bats, all represent important reservoirs of rabies virus. In contrast, rabies virus has never been detected in Old World bat populations, despite being endemic in terrestrial mammals. Instead, both insectivorous and frugivorous bat species across the Old World appear to act as reservoirs for the non-rabies lyssaviruses. In this chapter, we describe the association of the different lyssaviruses with different bat species across the world, classifying bat species by their feeding behavior.

Conservation of a unique mechanism of immune evasion across the Lyssavirus genus

The evasion of host innate immunity by Rabies virus, the prototype of the genus Lyssavirus, depends on a unique mechanism of selective targeting of interferon-activated STAT proteins by the viral phosphoprotein (P-protein). However, the immune evasion strategies of other lyssaviruses, including several lethal human pathogens, are unresolved. Here, we show that this mechanism is conserved between the most distantly related members of the genus, providing important insights into the pathogenesis and potential therapeutic targeting of lyssaviruses.

Molecular phylogenetics of the lyssaviruses--insights from a coalescent approach

Technical improvements over the past 2 decades have enormously facilitated the generation of nucleotide sequence data for lyssavirus collections. These databases are amenable to methods of phylogenetic analysis, which attempt to define the taxonomic structure of this genus and predict the evolutionary relationships of current circulating strains. Coupled with a range of mathematical tools to explore the appropriateness of nucleotide substitution models and test for positive selection, the evolutionary process is being explored in detail. Despite the potential for high viral mutation levels, the operation of purifying selection appears to effectively constrain lyssavirus evolution. The recent development of coalescent theory has provided additional approaches to data analysis whereby the time frame of emergence of viral lineages can be most reliably estimated. Such studies suggest that all currently circulating rabies viruses have emerged within the past 1500 years. Moreover, through the capability of analyzing viral population dynamics and determining patterns of population size variation, coalescent approaches can provide insight into the demographics of viral outbreaks. Whereas human-assisted movement of reservoir host species has clearly facilitated transfer of rabies between continents, topographical landscape features significantly influence the rate and extent of contiguous disease spread. Together with empirical studies on virus diversity, the application of coalescent approaches will help to better understand lyssavirus emergence, evolution, and spread. In particular, such methods are presently facilitating exploration of the factors operating to limit the ability of lyssaviruses to establish new persistent virus-host associations and ultimately control the emergence of new species of this genus.

Bats and lyssaviruses

Numerous bat species have been identified as important reservoirs of zoonotic viral pathogens. Rabies and rabies-related viruses constitute one of the most important viral zoonoses and pose a significant threat to public health across the globe. Whereas rabies virus (RABV) appears to be restricted to bats of the New World, related lyssavirus species have not been detected in the Americas and have only been detected in bat populations across Africa, Eurasia, and Australia. Currently, 11 distinct species of lyssavirus have been identified, 10 of which have been isolated from bat species and all of which appear to be able to cause encephalitis consistent with that seen with RABV infection of humans. In contrast, whereas lyssaviruses are apparently able to cause clinical disease in bats, it appears that these lyssaviruses may also be able to circulate within bat populations in the absence of clinical disease. This feature of these highly encephalitic viruses, alongside many other aspects of lyssavirus infection in bats, is poorly understood. Here, we review what is known of the complex relationship between bats and lyssaviruses, detailing both natural and experimental infections of these viruses in both chiropteran and nonchiropteran models. We also discuss potential mechanisms of virus excretion, transmission both to conspecifics and spill-over of virus into nonvolant species, and mechanisms of maintenance within bat populations. Importantly, we review the significance of neutralizing antibodies reported within bat populations and discuss the potential mechanisms by which highly neurovirulent viruses such as the lyssaviruses are able to infect bat species in the absence of clinical disease.

Bats, emerging infectious diseases, and the rabies paradigm revisited

The significance of bats as sources of emerging infectious diseases has been increasingly appreciated, and new data have been accumulated rapidly during recent years. For some emerging pathogens the bat origin has been confirmed (such as lyssaviruses, henipaviruses, coronaviruses), for other it has been suggested (filoviruses). Several recently identified viruses remain to be ‘orphan’ but have a potential for further emergence (such as Tioman, Menangle, and Pulau viruses). In the present review we summarize information on major bat-associated emerging infections and discuss specific characteristics of bats as carriers of pathogens (from evolutionary, ecological, and immunological positions). We also discuss drivers and forces of an infectious disease emergence and describe various existing and potential approaches for control and prevention of such infections at individual, populational, and societal levels.

Shimoni bat virus, a new representative of the Lyssavirus genus

During 2009, 616 bats representing at least 22 species were collected from 10 locations throughout Kenya. A new lyssavirus, named Shimoni bat virus (SHIBV), was isolated from the brain of a dead Commerson's leaf-nosed bat (Hipposideros commersoni), found in a cave in the coastal region of Kenya. Genetic distances and phylogenetic reconstructions, implemented for each gene and for the concatenated alignment of all five structural genes (N, P, M, G and L), demonstrated that SHIBV cannot be identified with any of the existing species, but rather should be considered an independent species within phylogroup II of the Lyssavirus genus, most similar to Lagos bat virus (LBV). Antigenic reaction patterns with anti-nucleocapsid monoclonal antibodies corroborated these distinctions. In addition, new data on the diversity of LBV suggests that this species may be subdivided quantitatively into three separate genotypes. However, the identity values alone are not considered sufficient criteria for demarcation of new species within LBV.

Complete genome sequence of a raccoon rabies virus isolate

The entire genome of a mid-Atlantic raccoon strain rabies virus (RRV) isolated in Canada was sequenced; this is the second North American wildlife rabies virus isolate to be fully characterized. The overall organization and length of the genome was similar to that of other lyssaviruses. The nucleotide sequence identity of the raccoon strain ranged between 32.7% and 85.0% when compared to other lyssaviruses, while the deduced amino acid sequence identity ranged between 22.9% and 94.2% with the nucleoprotein and polymerase being the most conserved. Notable features of RRV include the phosphoprotein's four amino acid extension compared to most other rabies viruses, and a nucleotide substitution immediately prior to the normal start codon that results in an additional methionine at the beginning of the L protein. This is the first report of the RRV L gene sequence and its 2128 amino acid product. Rates of non-synonymous and synonymous nucleotide changes within the lyssavirus L gene identified the conserved blocks II, III and IV as being most constrained. Analysis of L gene codon substitution patterns favoured models that supported positive selection, but only one site, corresponding to Leu62 of the RRV L protein, was identified as being under weak positive selection.

Complete genomes of Aravan, Khujand, Irkut and West Caucasian bat viruses, with special attention to the polymerase gene and non-coding regions

The purpose of this study was to generate complete genome sequences of Aravan (ARAV), Khujand (KHUV), Irkut (IRKV) and West Caucasian bat (WCBV) viruses, and to compare them with genomes of other lyssaviruses. We focused on RNA-dependent RNA-polymerase (L) and non-coding regions, because other genes of these viruses have been described previously. The L protein is organized into six conserved blocks (I-VI), previously detected in all Mononegavirales. Furthermore, lyssaviruses have two additional conserved regions, L1 and L2, located in the COOH part of the L. L1 may be responsible for methylation of viral mRNA cap structures, whereas the significance of L2 is unclear. Phylogenetic patterns based on the L are similar to those described for the nucleoprotein. The WCBV is the most divergent member of the genus. Besides phylogeny, it has a short trailer region (57 nucleotides versus 69-70 nucleotides in other lyssaviruses) and different intergenic region lengths, including an exceptionally long non-coding region of the glycoprotein (697 nucleotides) containing a potential open reading frame of 180 nucleotides. The absence of a flanking transcription initiation signal, as well as Northern and Western blot data, suggests that this region is not independently transcribed but is a part of G mRNA.

Genomic diversity and evolution of the lyssaviruses

Lyssaviruses are RNA viruses with single-strand, negative-sense genomes responsible for rabies-like diseases in mammals. To date, genomic and evolutionary studies have most often utilized partial genome sequences, particularly of the nucleoprotein and glycoprotein genes, with little consideration of genome-scale evolution. Herein, we report the first genomic and evolutionary analysis using complete genome sequences of all recognised lyssavirus genotypes, including 14 new complete genomes of field isolates from 6 genotypes and one genotype that is completely sequenced for the first time. In doing so we significantly increase the extent of genome sequence data available for these important viruses. Our analysis of these genome sequence data reveals that all lyssaviruses have the same genomic organization. A phylogenetic analysis reveals strong geographical structuring, with the greatest genetic diversity in Africa, and an independent origin for the two known genotypes that infect European bats. We also suggest that multiple genotypes may exist within the diversity of viruses currently classified as 'Lagos Bat'. In sum, we show that rigorous phylogenetic techniques based on full length genome sequence provide the best discriminatory power for genotype classification within the lyssaviruses.

Lagos bat virus in Kenya

During lyssavirus surveillance, 1,221 bats of at least 30 species were collected from 25 locations in Kenya. One isolate of Lagos bat virus (LBV) was obtained from a dead Eidolon helvum fruit bat. The virus was most similar phylogenetically to LBV isolates from Senegal (1985) and from France (imported from Togo or Egypt; 1999), sharing with these viruses 100% nucleoprotein identity and 99.8 to 100% glycoprotein identity. This genome conservancy across space and time suggests that LBV is well adapted to its natural host species and that populations of reservoir hosts in eastern and western Africa have sufficient interactions to share pathogens. High virus concentrations, in addition to being detected in the brain, were detected in the salivary glands and tongue and in an oral swab, suggesting that LBV is transmitted in the saliva. In other extraneural organs, the virus was generally associated with innervations and ganglia. The presence of infectious virus in the reproductive tract and in a vaginal swab implies an alternative opportunity for transmission. The isolate was pathogenic for laboratory mice by the intracerebral and intramuscular routes. Serologic screening demonstrated the presence of LBV-neutralizing antibodies in E. helvum and Rousettus aegyptiacus fruit bats. In different colonies the seroprevalence ranged from 40 to 67% and 29 to 46% for E. helvum and R. aegyptiacus, respectively. Nested reverse transcription-PCR did not reveal the presence of viral RNA in oral swabs of bats in the absence of brain infection. Several large bat roosts were identified in areas of dense human populations, raising public health concerns for the potential of lyssavirus infection.

Genetic heterogeneity of Russian, Estonian and Finnish field rabies viruses

Thirty-five field rabies virus strains were collected in recent years in different regions of the Russian Federation in order to characterize their genetic heterogeneity and to study their molecular epidemiology. In addition to the Russian viruses, seven archive samples from Estonia and Finland and two Russian vaccine strains were also included in the study. The viruses collected were subjected to two different reverse transcription-polymerase chain reaction tests, the amplicons were sequenced and the sequences were analysed phylogenetically. Among the field viruses studied, two main phylogenetic groups were found and designated as Pan-Eurasian and Caucasian according to their geographic origin. The Pan-Eurasian group, comprising some reference viruses from Europe, was further divided into four subgroups. All of the vaccine strains were clearly different from the field strains. No recombination between the field and vaccine virus strains was observed. The data obtained here show the critical role of geographical isolation and limitation for the genetic clustering and evolution of the rabies virus and also help in predicting its distribution from rabies-affected areas to rabies-free areas.

Comparative analysis of the full genome sequence of European bat lyssavirus type 1 and type 2 with other lyssaviruses and evidence for a conserved transcription termination and polyadenylation motif in the G-L 3' non-translated region

We report the first full-length genomic sequences for European bat lyssavirus type-1 (EBLV-1) and type-2 (EBLV-2). The EBLV-1 genomic sequence was derived from a virus isolated from a serotine bat in Hamburg, Germany, in 1968 and the EBLV-2 sequence was derived from a virus isolate from a human case of rabies that occurred in Scotland in 2002. A long-distance PCR strategy was used to amplify the open reading frames (ORFs), followed by standard and modified RACE (rapid amplification of cDNA ends) techniques to amplify the 3' and 5' ends. The lengths of each complete viral genome for EBLV-1 and EBLV-2 were 11 966 and 11 930 base pairs, respectively, and follow the standard rhabdovirus genome organization of five viral proteins. Comparison with other lyssavirus sequences demonstrates variation in degrees of homology, with the genomic termini showing a high degree of complementarity. The nucleoprotein was the most conserved, both intra- and intergenotypically, followed by the polymerase (L), matrix and glyco- proteins, with the phosphoprotein being the most variable. In addition, we have shown that the two EBLVs utilize a conserved transcription termination and polyadenylation (TTP) motif, approximately 50 nt upstream of the L gene start codon. All available lyssavirus sequences to date, with the exception of Pasteur virus (PV) and PV-derived isolates, use the second TTP site. This observation may explain differences in pathogenicity between lyssavirus strains, dependent on the length of the untranslated region, which might affect transcriptional activity and RNA stability.

Surveillance and response to disease emergence

New and emerging infectious diseases affect humans, domestic animals, livestock and wildlife and can have a significant impact on health, trade and biodiversity. Of the emerging infectious diseases of humans, 75% are zoonotic, with wildlife being an increasingly important source of inter-species transmission. Recent animal health emergencies have highlighted the vulnerability of the livestock sector to the impact of infectious diseases and the associated risks to human health. Outbreaks resulting from wildlife trade have resulted in enormous economic losses globally. On a global level, the human health sector lags behind the animal health sector in the assessment of potential threats, although substantive differences exist among countries in the state of national preparedness planning for emerging diseases. The lack of surveillance data on emerging zoonoses from many developing countries means that the burden of human, livestock and wildlife disease is underestimated and opportunities for control interventions thereby limited. In the context of emerging zoonoses, comprehensive risk assessments are needed to identify the animal-human and animal-animal interfaces where transmission of infectious agents occurs and the feasibility of risk reduction interventions. The impact of emerging diseases can be minimised through a well-prepared and strong public health system and similar systems developed by the livestock, wildlife and food safety sectors. National animal disease emergencies, especially those that spill over to affect human health, require a whole-of-government approach for effective disease containment. As it is highly likely that zoonoses and animal diseases with the potential to affect human health will continue to emerge, surveillance and response systems for emerging zoonotic diseases will need to be strengthened and maintained at national and international levels. Applied research, linked across the human, livestock and wildlife sectors, is needed to inform preparedness planning and the development of evidence-based approaches to zoonotic disease prevention and control.

Molecular diagnosis of lyssaviruses and sequence comparison of Australian bat lyssavirus samples

OBJECTIVE

To evaluate and implement molecular diagnostic tests for the detection of lyssaviruses in Australia.

DESIGN

A published hemi-nested reverse transcriptase polymerase chain reaction (RT-PCR) for the detection of all lyssavirus genotypes was modified to a fully nested RT-PCR format and compared with the original assay. TaqMan assays for the detection of Australian bat lyssavirus (ABLV) were compared with both the nested and hemi-nested RT-PCR assays. The sequences of RT-PCR products were determined to assess sequence variations of the target region (nucleocapsid gene) in samples of ABLV originating from different regions.

RESULTS

The nested RT-PCR assay was highly analytically specific, and at least as analytically sensitive as the hemi-nested assay. The TaqMan assays were highly analytically specific and more analytically sensitive than either RT-PCR assay, with a detection level of approximately 10 genome equivalents per microl. Sequence of the first 544 nucleotides of the nucleocapsid protein coding sequence was obtained from all samples of ABLV received at Australian Animal Health Laboratory during the study period.

CONCLUSION

The nested RT-PCR provided a means for molecular diagnosis of all tested genotypes of lyssavirus including classical rabies virus and Australian bat lyssavirus. The published TaqMan assay proved to be superior to the RT-PCR assays for the detection of ABLV in terms of analytical sensitivity. The TaqMan assay would also be faster and cross contamination is less likely. Nucleotide sequence analyses of samples of ABLV from a wide geographical range in Australia demonstrated the conserved nature of this region of the genome and therefore the suitability of this region for molecular diagnosis.

Emerging zoonotic encephalitis viruses: lessons from Southeast Asia and Oceania

The last decade of the 20th Century saw the introduction of an unprecedented number of encephalitic viruses emerge or spread in the Southeast Asian and Western Pacific regions (Mackenzie et al, 2001; Solomon, 2003a). Most of these viruses are zoonotic, either being arthropod-borne viruses or bat-borne viruses. Thus Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, has spread through the Indonesian archipelago to Papua New Guinea (PNG) and to the islands of the Torres Strait of northern Australia, to Pakistan, and to new areas in the Indian subcontinent; a strain of tick-borne encephalitis virus (TBEV) was described for the first time in Hokkaido, Japan; and a novel mosquito-borne alphavirus, Me Tri virus, was described from Vietnam. Three novel bat-borne viruses emerged in Australia and Malaysia; two, Hendra and Nipah viruses, represent the first examples of a new genus in the family Paramyxoviridae, the genus Henipaviruses, and the third, Australian bat lyssavirus (ABLV) is new lyssavirus closely related to classical rabies virus. These viruses will form the body of this brief review.

Australian bat lyssavirus: a recently discovered new rhabdovirus

Australian bat lyssavirus (ABLV), first identified in 1996, has been associated with two human fatalities. ABLV is genetically and serologically distinct from, but is closely related to, classical rabies. It has a bullet-shaped morphology by electron microscopy. There are two strains of ABLV known: one circulates in frugivorous bats, sub-order Megachiroptera, and the other circulates in the smaller, mainly insectivorous bats, sub-order Microchiroptera. Each strain has been associated with one human fatality. Surveillance indicates infected bats are widespread at a low frequency on the Australian mainland. It is unclear how long ABLV has been present in Australia, although molecular clock studies suggest the two strains separated 950 or 1,700 years ago based on synonymous or non-synonymous nucleotide changes, respectively. Recent serological surveys suggest a closely related virus may exist in the Philippines. Due to demonstrated cross-protection in mice, rabies vaccine is used to prevent infection. Rabies post-exposure prophylaxis (PEP) protocols have been adopted for when a human is scratched or bitten by a suspect bat. A long-term commitment to public health programs that test bats that have been involved in scratch or bite incidents, followed by PEP if appropriate, will be necessary to minimise further human infection.

Genetic comparison of the rhabdoviruses from animals and plants

There are more than 160 viral species in the Rhabdovidae family, most of which can be grouped into one of the six genera including Vesiculovirus, Lyssavirus, Ephemerovirus, Novirhabdovirus, Cytorhabdovirus, and Nucleorhabdovirus. These viruses are not only morphologically similar but also genetically related. Analysis of viral genes shows that rhabdoviruses are more closely related to each other than to viruses in other families. With the development of reverse genetics, the functions of many cis- and trans-elements important in the process of viral transcription and replication have been clearly defined such as the leader, trailer, and the intergenic sequences. Furthermore, it has been shown that there are two entry sites for the RNA-dependent RNA polymerase: 3' entry for leader synthesis and RNA replication, and direct entry at the N gene start sequence for transcription of the monocistronic mRNAs.

Phylogenetic relationships of Irkut and West Caucasian bat viruses within the Lyssavirus genus and suggested quantitative criteria based on the N gene sequence for lyssavirus genotype definition

The nucleoprotein (N), phosphoprotein (P) and glycoprotein (G) genes of Irkut and West Caucasian bat viruses (WCBV) were sequenced and compared with those of other lyssaviruses. N gene nucleotide identities provided unequivocal separation of all lyssavirus genotypes with an identity threshold of 82%. On this basis, Irkut virus should be considered as a new genotype with particular relatedness to genotypes 4 and 5 (78.0-78.6% identity for N gene nucleotides and 90.4-92.6% for amino acids). Furthermore, genotypes 4-6, together with Aravan, Khujand and Irkut viruses, present a solid phylogroup of Old World bat lyssaviruses. This relationship is apparent using all three viral genes, and causes overlap between intragenotype and intergenotype identities for the P gene (Aravan, Khujand viruses and genotype 6) and for the G gene (Aravan, Khujand, genotypes 5 and 6). WCBV is the most divergent of known lyssaviruses with only limited relatedness to genotypes 2 and 3.

Novel viral encephalitides associated with bats (Chiroptera)--host management strategies

Several novel viruses recently described in bats of the genus Pteropus (sub-order Megachiroptera) in Australia and southeast Asia cause encephalitic disease in animals and humans. These viruses include Hendra virus and Nipah virus (genus Henipavirus, family Paramyxoviridae) and Australian bat lyssavirus (ABLV; genus Lyssavirus, family Rhabdoviridae). Broadly, strategies for disease prevention and control in the spillover host are directed at minimising direct or indirect contact with the natural host, improving farm-gate and on-farm biosecurity, and better disease recognition and diagnosis. Additional strategies for ABLV include the use of rabies vaccine for effective pre- and post-exposure prophylaxis in humans. Effective management strategies in the natural host are predicated on an understanding of the ecology of the disease in the natural host, and the identification and avoidance of factors putatively associated with emergence, such as habitat loss, land use change and demographic shifts. A possible future management strategy for ABLV in reservoir populations is immunisation using bait or plant-derived vaccination.

Emerging encephalitogenic viruses: lyssaviruses and henipaviruses transmitted by frugivorous bats

Three newly recognized encephalitogenic zoonotic viruses spread from fruit bats of the genus Pteropus (order Chiroptera, suborder Megachiroptera) have been recognised over the past decade. These are: Hendra virus, formerly named equine morbillivirus, which was responsible for an outbreak of disease in horses and humans in Brisbane, Australia, in 1994; Australian bat lyssavirus, the cause of a severe acute encephalitis, in 1996; and Nipah virus, the cause of a major outbreak of encephalitis and pulmonary disease in domestic pigs and people in peninsula Malaysia in 1999. Hendra and Nipah viruses have been shown to be the first two members of a new genus, Henipavirus, in the family Paramyxoviridae, subfamily Paramyxovirinae, whereas Australian bat lyssavirus is closely related antigenically to classical rabies virus in the genus Lyssavirus, family Rhabdoviridae, although it can be distinguished on genetic grounds. Hendra and Nipah viruses have neurological and pneumonic tropisms. The first humans and equids with Hendra virus infections died from acute respiratory disease, whereas the second human patient died from an encephalitis. With Nipah virus, the predominant clinical syndrome in humans was encephalitic rather than respiratory, whereas in pigs, the infection was characterised by acute fever with respiratory involvement with or without neurological signs. Two human infections with Australian bat lyssavirus have been reported, the clinical signs of which were consistent with classical rabies infection and included a diffuse, non-suppurative encephalitis. Many important questions remain to be answered regarding modes of transmission, pathogenesis, and geographic range of these viruses.

Genetic analysis of European bat lyssavirus type 1 isolates from France

European bat lyssavirus type 1a (EBLV-1a) was first identified in central France from a serotine bat (Eptesicus serotinus) collected at the end of 2002. Rabies was diagnosed by reference rabies diagnosis methods and molecular tools. Phylogenetic analysis of 14 viral isolates obtained from French bats infected with EBLV-1 between 1989 and the end of 2002 against 47 nucleoprotein sequences showed a north-west to east distribution of EBLV-1a virus and a south to north distribution of EBLV-1b virus, isolates of which could be divided into two groups: group 1 in north-eastern France and group 2 in central and north-western France.

Bat lyssaviruses (Aravan and Khujand) from Central Asia: phylogenetic relationships according to N, P and G gene sequences

Bat lyssaviruses Aravan and Khujand were isolated in southern Kyrgyzstan in 1991 and in northern Tajikistan in 2001, respectively. Preliminary studies with anti-nucleocapsid monoclonal antibodies suggested that the viruses were distinct from other lyssavirus serotypes. These data were supported by sequencing of the N gene of Aravan virus. In the present study, we sequenced the entire N, P and G genes of both Aravan and Khujand viruses and compared them with respective sequences of other lyssaviruses available from GenBank. The results suggested that each virus should be considered as a newly recognized genotype according to the current approaches for genotype definition (amount of nucleotide identity of the N gene and bootstrap support of joining to certain phylogenetic groups). Use of different phylogenetic methods and comparison of different parts of the genomes generally suggested that Khujand virus was mainly related to genotype 6, while Aravan virus, on the one hand, was related to Khujand virus, and, on the other hand, demonstrated moderate similarity to genotypes 4, 5 and 6. The potential significance of these new lyssaviruses for veterinary and public health should not be underestimated.