Isolation of Kaeng Khoi virus from dead Chaerephon plicata bats in Cambodia

Eptesipox virus-associated lesions in naturally infected big brown bats

Bats have many unique qualities amongst mammals; one of particular importance is their reported tolerance to viruses without developing disease. Here, the authors present evidence to the contrary by describing and demonstrating viral nucleic acids within lesions from eptesipox virus (EfPV) infection in big brown bats. One hundred and thirty bats submitted for necropsy from Saskatchewan, Canada, between 2017 and 2021 were screened for EfPV by polymerase chain reaction (PCR); 2 had amplifiable poxvirus DNA. The lesions associated with infection were oral and pharyngeal ulcerations and joint swelling in 2/2 and 1/2 cases, respectively. These changes were nonspecific for poxvirus infection, although intracytoplasmic viral inclusion bodies within the epithelium, as observed in 2/2 bats, are diagnostic when present. Viral nucleic acids, detected by in situ hybridization (ISH), were observed in the epithelium adjacent to ulcerative lesions from both cases and within the joint proliferation of 1 case. A new isolate of EfPV was obtained from 1 case and its identity was confirmed with electron microscopy and whole genome sequencing. Juxtanuclear replication factories were observed in most cells; however, rare intranuclear virus particles were also observed. The significance of the presence of virus particles within the nucleus is uncertain. Whole genome assembly indicated that the nucleotide sequence of the genome of this EfPV isolate was 99.7% identical to a previous isolate from big brown bats in Washington, USA between 2009 and 2011. This work demonstrates that bats are not resistant to the development of disease with viral infections and raises questions about the dogma of poxvirus intracytoplasmic replication.

Cimicids of Medical and Veterinary Importance

Members of the Cimicidae family are significant pests for mammals and birds, and they have attracted medical and veterinary interest. A number of recent studies have investigated bed bugs, due to their dramatic resurgence all over the world. Indeed, bed bugs are of significant public health and socioeconomic importance since they lead to financial burdens and dermatological complications and may have mental and psychological consequences. It is important to note that certain cimicids with a preference for specific hosts (birds and bats) use humans as an alternative host, and some cimicids have been reported to willingly feed on human blood. In addition, members of the Cimicidae family can lead to economic burdens and certain species are the vectors for pathogens responsible for diseases. Therefore, in this review, we aim to provide an update on the species within the Cimicidae family that have varying medical and veterinary impacts, including their distribution and their associated microorganisms. Various microbes have been documented in bed bugs and certain important pathogens have been experimentally documented to be passively transmitted by bed bugs, although no conclusive evidence has yet associated them with epidemiological outbreaks. Additionally, among the studied cimicids (bat bugs, chicken bugs, and swallow bugs), only the American swallow bug has been considered to be a vector of several arboviruses, although there is no proven evidence of transmission to humans or animals. Further studies are needed to elucidate the reason that certain species in the Cimicidae family cannot be biologically involved in transmission to humans or animals. Additional investigations are also required to better understand the roles of Cimicidae family members in the transmission of human pathogens in the field.

Revising the paradigm: Are bats really pathogen reservoirs or do they possess an efficient immune system?

While bats are often referred to as reservoirs of viral pathogens, a meta-analysis of the literature reveals many cases in which there is not enough evidence to claim so. In many cases, bats are able to confront viruses, recover, and remain immune by developing a potent titer of antibodies, often without becoming a reservoir. In other cases, bats might have carried an ancestral virus that at some time point might have mutated into a human pathogen. Moreover, bats exhibit a balanced immune response against viruses that have evolved over millions of years. Using genomic tools, it is now possible to obtain a deeper understanding of that unique immune system and its variability across the order Chiroptera. We conclude, that with the exception of a few viruses, bats pose little zoonotic danger to humans and that they operate a highly efficient anti-inflammatory response that we should strive to understand.

Viral Ecology and Natural Infection Dynamics of Kaeng Khoi Virus in Cave-Dwelling Wrinkle-Lipped Free-Tailed Bats (Chaerephon plicatus) in Thailand

Kaeng Khoi virus (KKV; Order: Bunyavirales), is an endemic viral infection of the wrinkle-lipped free-tailed bat (Chaerephon plicatus aka Tadarida plicata plicata). Little is known about the ecology and maintenance of KKV within the bat population, nor the infection dynamics and transmission among bats or between bats and other vertebrates. Therefore, KKV was studied in Kaeng Khoi cave, Saraburi province, Thailand, during 1973–1974 with the objectives to (1) characterize the seasonal infection rates of KKV in the context of the bat population ecology, and (2) describe the infection dynamics and viral shedding by naturally- and experimentally-infected bats. To this end, the free-tailed bat population was estimated by a series of timed photographs taken during the evening exodus. The case population of 900,000 adult bats doubled at the time of weaning of the young and returned to its previous level soon thereafter. The newborn bats had neutralizing antibodies to KKV that were likely to be maternal in origin. The KKV antibody prevalence in adult bats was high (69–91%) in March–May and low (29–40%) in August and September. Kaeng Khoi virus was isolated from 75% of dead and 50% of moribund bats, but was not found in nearly 400 apparently healthy bats. Virus was present in saliva, urine and blood of most of the naturally-moribund bats tested. Consistent with observations from naturally-infected bats, experimental infection of bats with KKV revealed significant liver pathology, also suggestive that this is not a benign infection. Kaeng Khoi virus is an endemic, year-round infection maintained by the annual recruitment of a large number of immunologically-naïve juvenile bats. Moreover, it produces an acute infection in the bat, either leading to death by hepatitis, or immunity.

Investigations on Vector-Borne and Aerosol Transmission Potential of Kaeng Khoi Virus in Cave-Dwelling Wrinkle-Lipped Free-Tailed Bats (Chaerephon plicatus) in Thailand

Kaeng Khoi virus (KKV; Order: Bunyavirales, Family: Peribunyaviridae, Genus: Orthobunyavirus), is an endemic viral infection of the wrinkle-lipped free-tailed bat (Chaerephon plicatus; also known as Tadarida plicata plicata). Viral isolates from bat bugs (Family: Cimicidae) suggest vector-borne transmission, but in general little is known about the ecology of KKV and seroprevalence in the local human and animal populations. Transmission studies and a serosurvey were carried out in Kaeng Khoi cave, Saraburi province, Thailand, during 1973–1974. Experimental transmission studies were performed with bat bugs captured within the cave to determine the potential for vector-borne transmission, and sentinel laboratory mice placed inside arthropod-proof cages within the cave to assess the potential for aerosolized transmission. Antibodies to KKV were detected in roof rats (Rattus rattus) inhabiting the cave, in dogs living in the valley, and in humans. Freshly collected cimicids were positive for KKV, but the virus did not replicate in laboratory-inoculated bugs. Sentinel mice placed in Kaeng Khoi cave in open cages consistently became infected with KKV, as determined by the development of neutralizing antibodies. Mice placed in arthropod-proof cages also developed antibodies, indicating the possibility of airborne transmission of KKV.

Bat virome research: the past, the present and the future

Bats have been increasingly recognised as an exceptional reservoir for emerging zoonotic viruses for the past few decades. Recent studies indicate that the unique bat immune system may be partially responsible for their ability to co-exist with viruses with minimal or no clinical diseases. In this review, we discuss the history and importance of bat virome studies and contrast the vast difference between such studies before and after the introduction of next generation sequencing (NGS) in this area of research. We also discuss the role of discovery serology and high-throughput single cell RNA-seq in future bat virome research.

Bat Flies of the Family Streblidae (Diptera: Hippoboscoidea) Host Relatives of Medically and Agriculturally Important "Bat-Associated" Viruses

Bat flies (Hippoboscoidea: Nycteribiidae and Streblidae) are obligate hematophagous ectoparasites of bats. We collected streblid bat flies from the New World (México) and the Old World (Uganda), and used metagenomics to identify their viruses. In México, we found méjal virus (Rhabdoviridae; Vesiculovirus), Amate virus (Reoviridae: Orbivirus), and two unclassified viruses of invertebrates. Méjal virus is related to emerging zoonotic encephalitis viruses and to the agriculturally important vesicular stomatitis viruses (VSV). Amate virus and its sister taxon from a bat are most closely related to mosquito- and tick-borne orbiviruses, suggesting a previously unrecognized orbivirus transmission cycle involving bats and bat flies. In Uganda, we found mamucuso virus (Peribunyaviridae: Orthobunyavirus) and two unclassified viruses (a rhabdovirus and an invertebrate virus). Mamucuso virus is related to encephalitic viruses of mammals and to viruses from nycteribiid bat flies and louse flies, suggesting a previously unrecognized orthobunyavirus transmission cycle involving hippoboscoid insects. Bat fly virus transmission may be neither strictly vector-borne nor strictly vertical, with opportunistic feeding by bat flies occasionally leading to zoonotic transmission. Many "bat-associated" viruses, which are ecologically and epidemiologically associated with bats but rarely or never found in bats themselves, may actually be viruses of bat flies or other bat ectoparasites.

Current Arboviral Threats and Their Potential Vectors in Thailand

Arthropod-borne viral diseases (arboviruses) are a public-health concern in many regions of the world, including Thailand. This review describes the potential vectors and important human and/or veterinary arboviruses in Thailand. The medically important arboviruses affect humans, while veterinary arboviruses affect livestock and the economy. The main vectors described are mosquitoes, but other arthropods have been reported. Important mosquito-borne arboviruses are transmitted mainly by members of the genus Aedes (e.g., dengue, chikungunya, and Zika virus) and Culex (e.g., Japanese encephalitis, Tembusu and West Nile virus). While mosquitoes are important vectors, arboviruses are transmitted via other vectors, such as sand flies, ticks, cimicids (Family Cimicidae) and Culicoides. Veterinary arboviruses are reported in this review, e.g., duck Tembusu virus (DTMUV), Kaeng Khoi virus (KKV), and African horse sickness virus (AHSV). During arbovirus outbreaks, to target control interventions appropriately, it is critical to identify the vector(s) involved and their ecology. Knowledge of the prevalence of these viruses, and the potential for viral infections to co-circulate in mosquitoes, is also important for outbreak prediction.

Emerging orthobunyaviruses associated with CNS disease

The Orthobunyavirus genus comprises a wide range of arthropod-borne viruses which are prevalent worldwide and commonly associated with central nervous system (CNS) disease in humans and other vertebrates. Several orthobunyaviruses have recently emerged and increasingly more will likely do so in the future. Despite this large number, an overview of these viruses is currently lacking, making it challenging to determine importance from a One Health perspective. Causality is a key feature of determining importance, yet classical tools are unfit to evaluate the causality of orthobunyaviral CNS disease. Therefore, we aimed to provide an overview of orthobunyaviral CNS disease in vertebrates and objectify the causality strength of each virus. In total, we identified 27 orthobunyaviruses described in literature to be associated with CNS disease. Ten were associated with disease in multiple host species of which seven included humans. Seven viruses were associated with both congenital and postnatal CNS disease. CNS disease-associated orthobunyaviruses were spread across all known Orthobunyavirus serogroups by phylogenetic analyses. Taken together, these results indicate that orthobunyaviruses may have a common tendency to infect the CNS of vertebrates. Next, we developed six tailor-made causality indicators and evaluated the causality strength of each of the identified orthobunyaviruses. Nine viruses had a 'strong' causality score and were deemed causal. Eight had a 'moderate' and ten a 'weak' causality score. Notably, there was a lack of case-control studies, which was only available for one virus. We, therefore, stress the importance of proper case-control studies as a fundamental aspect of proving causality. This comprehensible overview can be used to identify orthobunyaviruses which may be considered causal, reveal research gaps for viruses with moderate to low causality scores, and provide a framework to evaluate the causality of orthobunyaviruses that may newly emerge in the future.

Diversity and Evolution of Viral Pathogen Community in Cave Nectar Bats (Eonycteris spelaea)

Bats are unique mammals, exhibit distinctive life history traits and have unique immunological approaches to suppression of viral diseases upon infection. High-throughput next-generation sequencing has been used in characterizing the virome of different bat species. The cave nectar bat, Eonycteris spelaea, has a broad geographical range across Southeast Asia, India and southern China, however, little is known about their involvement in virus transmission. Here we investigate the diversity and abundance of viral communities from a colony of Eonycteris spelaea residing in Singapore. Our results detected 47 and 22 different virus families from bat fecal and urine samples, respectively. Among these, we identify a large number of virus families including Adenoviridae, Flaviviridae, Reoviridae, Papillomaviridae, Paramyxoviridae, Parvoviridae, Picornaviridae, and Polyomaviridae. In most cases, viral sequences from Eonycteris spelaea are genetically related to a group of bat viruses from other bat genera (e.g., Eidolon, Miniopterus, Rhinolophus and Rousettus). The results of this study improve our knowledge of the host range, spread and evolution of several important viral pathogens. More significantly, our findings provide a baseline to study the temporal patterns of virus shedding and how they correlate with bat phenological trends.

Can Bats Serve as Reservoirs for Arboviruses?

Bats are known to harbor and transmit many emerging and re-emerging viruses, many of which are extremely pathogenic in humans but do not cause overt pathology in their bat reservoir hosts: henipaviruses (Nipah and Hendra), filoviruses (Ebola and Marburg), and coronaviruses (SARS-CoV and MERS-CoV). Direct transmission cycles are often implicated in these outbreaks, with virus shed in bat feces, urine, and saliva. An additional mode of virus transmission between bats and humans requiring further exploration is the spread of disease via arthropod vectors. Despite the shared ecological niches that bats fill with many hematophagous arthropods (e.g. mosquitoes, ticks, biting midges, etc.) known to play a role in the transmission of medically important arboviruses, knowledge surrounding the potential for bats to act as reservoirs for arboviruses is limited. To this end, a comprehensive literature review was undertaken examining the current understanding and potential for bats to act as reservoirs for viruses transmitted by blood-feeding arthropods. Serosurveillance and viral isolation from either free-ranging or captive bats are described in relation to four arboviral groups (Bunyavirales, Flaviviridae, Reoviridae, Togaviridae). Further, ecological associations between bats and hematophagous viral vectors are characterized (e.g. bat bloodmeals in mosquitoes, ingestion of mosquitoes by bats, etc). Lastly, knowledge gaps related to hematophagous ectoparasites (bat bugs and bed bugs (Cimicidae) and bat flies (Nycteribiidae and Streblidae)), in addition to future directions for characterization of bat-vector-virus relationships are described.

Isolation and Identification of a Highly Divergent Kaeng Khoi Virus from Bat Flies (Eucampsipoda sundaica) in China

BACKGROUND

Kaeng Khoi virus (KKV), which belongs to the genus Orthobunyavirus, family Perbunyaviridae, was originally isolated from the brain tissue of bats and may cause infection in humans. In this study, the KKV strain WDBC1403 was isolated from bat flies (Eucampsipoda sundaica), ectoparasites of the bat Rousettus leschenaultia, collected from Yunnan Province of China at the Sino-Burmese border.

METHODS AND RESULTS

The bat fly specimens were ground and inoculated in culture cells. The WDBC1403 strain was shown to induce cytopathic effects in Vero, baby hamster kidney (BHK-21), and Tb1Lu cells, but not in C6/36 cells; however, viral gene amplification was detected in the supernatants of C6/36 cells. Using electron microscopy, the virus was determined to be spherical, enveloped, and 80-90 nm in diameter; it was also shown to form plaques in BHK-21 cells and the titer reached 1 × 10^6.57 plaque-forming units/mL 24 h after infection. The phylogenetic analysis showed that WDBC1403 is a KKV strain, but is independent of the original KKV strain (PSC-19). Viral genome analysis revealed that the nucleotide and amino acid sequence identities of the S, M, and L segments of WDBC1403 with PSC-19 were 88.2% and 96.1%, 76.7% and 85.0%, and 78.3% and 88.9%, respectively. Two amino acids were removed at the end of the open reading frame of the M segment, and 47 nucleotides were removed in the 3'-untranslated region of the M segment of the WDBC1403 strain compared with the PSC-19 strain.

CONCLUSIONS

The WDBC1403 strain is a highly divergent KKV strain, suggesting that there are a variety of KKV strains that exhibit molecular differences. Moreover, because of the large variations in nucleotide and amino acid sequence in the M segment, which encodes an important membrane protein, further research on antigenicity and pathogenicity in humans and animals is needed.

Distribution of bat-borne viruses and environment patterns

Environmental modifications are leading to biodiversity changes, loss and habitat disturbance. This in turn increases contacts between wildlife and hence the risk of transmission and emergence of zoonotic diseases. We analyzed the environment and land use using remote spatial data around the sampling locations of bats positive for coronavirus (21 sites) and astrovirus (11 sites) collected in 43 sites. A clear association between viruses and hosts was observed. Viruses associated to synanthropic bat genera, such as Myotis or Scotophilus were associated to highly transformed habitats with human presence while viruses associated to fruit bat genera were correlated with natural environments with dense forest, grassland areas and regions of high elevation. In particular, group C betacoronavirus were associated with mosaic habitats found in anthropized environments.

Isolation of Kaeng Khoi virus (KKV) from Eucampsipoda sundaica bat flies in China

A virus strain (WDBC1210) was isolated from specimens of bat flies (Eucampsipoda sundaica) associated with Leschenault's Rousette (Rousettus leschenaultii) in the China-Myanmar border area of Yunnan Province, China. Both BHK-21 and VeroE6 cells infected with WDBC1210 showed evident cytopathic effects (CPE), and the highest propagation titer was 1×10^5.6. The virus particles were spherical, 70nm in diameter. Virus plaques could be observed in BHK-21 cells. The whole genome of WDBC1210 contained three RNA segments: the small gene (S), 975 nucleotides long; the medium gene (M), 4568 nucleotides long; and the large gene (L), 6866 nucleotides long. The nucleotide homologies of the S, M, and L genes between WDBC1210 and the original isolate of Kaeng Khoi virus (KKV; PSC-19 strain) were 96.9%, 94.1%, and 95.2%, respectively. Phylogenetic analyses based on the S, M, and L segments indicated that WDBC1210 belongs within the same clade as the KKV strain PSC-19, a member of the Bunyaviridae family. This is the first report on the isolation of KKV from bat flies (Eucampsipoda sundaica) and from an inland area, nearly 2000km north from the original isolation site of KKV in Thailand, suggesting that KKV virus not only has a diverse set of vectors, but also a wide geographic distribution.

Isolation of a novel orthobunyavirus from bat flies (Eucampsipoda africana)

The Bunyaviridae family comprises viruses causing diseases of public and veterinary health importance, including viral haemorrhagic and arboviral fevers. We report the isolation, identification and genome characterization of a novel orthobunyavirus, named Wolkberg virus (WBV), from wingless bat fly ectoparasites (Eucampsipoda africana) of Egyptian fruit bats (Rousettus aegyptiacus) in South Africa. Complete genome sequence data of WBV suggests it is most closely related to two bat viruses (Mojuí dos Campos and Kaeng Khoi viruses) and an arbovirus (Nyando virus) previously shown to infect humans. WBV replicates to high titres in VeroE6 and C6-36 cells, characteristic of mosquito-borne arboviruses. These findings expand our knowledge of the diversity of orthobunyaviruses and their insect vector host range.

The cave microbiome as a source for drug discovery: Reality or pipe dream?

This review highlights cave habitats, cave microbiomes and their potential for drug discovery. Such studies face many challenges, including access to remote and pristine caves, and sample collection and transport. Inappropriate physical and chemical growth conditions in the laboratory for the isolation and cultivation of cave microorganisms pose many complications including length of cultivation; some cave microorganisms can take weeks and even months to grow. Additionally, DNA extraction from cave environmental samples may be difficult due to the high concentration of various minerals that are natural DNA blocking agents. Once cave microorganisms are grown in the lab, other problems often arise, such as maintenance of pure culture, consistency of antimicrobial activity and fermentation conditions for antimicrobial production. In this review, we suggest that, although based on what has been done in the field, there is potential in using cave microorganisms to produce antimicrobial agents, one needs to be highly committed and prepared.

Diversity of bat astroviruses in Lao PDR and Cambodia

Astroviruses are known to infect humans and a wide range of animal species, and can cause gastroenteritis in their hosts. Recent studies have reported astroviruses in bats in Europe and in several locations in China. We sampled 1876 bats from 17 genera at 45 sites from 14 and 13 provinces in Cambodia and Lao PDR respectively, and tested them for astroviruses. Our study revealed a high diversity of astroviruses among various Yangochiroptera and Yinpterochiroptera bats. Evidence for varying degrees of host restriction for astroviruses in bats was found. Furthermore, additional Pteropodid hosts were detected. The astroviruses formed distinct phylogenetic clusters within the genus Mamastrovirus, most closely related to other known bat astroviruses. The astrovirus sequences were found to be highly saturated indicating that phylogenetic relationships should be interpreted carefully. An astrovirus clustering in a group with other viruses from diverse hosts, including from ungulates and porcupines, was found in a Rousettus bat. These findings suggest that diverse astroviruses can be found in many species of mammals, including bats.

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Diverse astroviruses detected in bats in Lao PDR and Cambodia

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High polymorphism of astroviruses found in insectivorous and frugivorous bats

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High level of genome saturation and hypermutation potential evidenced in astrovirus

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Detection of additional astrovirus bat hosts, i.e. nectar bats from the genus Eonycteris

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Discovery of a new species of astrovirus in fruit bats (Rousettus sp.)

Molecular characterization of human pathogenic bunyaviruses of the Nyando and Bwamba/Pongola virus groups leads to the genetic identification of Mojuí dos Campos and Kaeng Khoi virus

Background

Human infection with Bwamba virus (BWAV) and the closely related Pongola virus (PGAV), as well as Nyando virus (NDV), are important causes of febrile illness in Africa. However, despite seroprevalence studies that indicate high rates of infection in many countries, these viruses remain relatively unknown and unstudied. In addition, a number of unclassified bunyaviruses have been isolated over the years often with uncertain relationships to human disease.

Methodology/Principal Findings

In order to better understand the genetic and evolutionary relationships among orthobunyaviruses associated with human disease, we have sequenced the complete genomes for all 3 segments of multiple strains of BWAV (n = 2), PGAV (n = 2) and NDV (n = 4), as well as the previously unclassified Mojuí dos Campos (MDCV) and Kaeng Khoi viruses (KKV). Based on phylogenetic analysis, we show that these viruses populate 2 distinct branches, one made up of BWAV and PGAV and the other composed of NDV, MDCV and KKV. Interestingly, the NDV strains analyzed form two distinct clades which differed by >10% on the amino acid level across all protein products. In addition, the assignment of two bat-associated bunyaviruses into the NDV group, which is clearly associated with mosquito-borne infection, led us to analyze the ability of these different viruses to grow in bat (RE05 and Tb 1 Lu) and mosquito (C6/36) cell lines, and indeed all the viruses tested were capable of efficient growth in these cell types.

Conclusions/Significance

On the basis of our analyses, it is proposed to reclassify the NDV strains ERET147 and YM176-66 as a new virus species. Further, our analysis definitively identifies the previously unclassified bunyaviruses MDCV and KKV as distinct species within the NDV group and suggests that these viruses may have a broader host range than is currently appreciated.

Bunyavirus infections cause febrile illnesses of varying severity worldwide; however, despite their public health importance most remain relatively unstudied. In order to clarify the genetic relationships among African orthobunyaviruses associated with human infection, we have sequenced multiple strains of Bwamba (BWAV), Pongola (PGAV) and Nyando virus (NDV). Based on genetic analysis we showed that, while different BWAV and PGAV virus strains are closely related, NDV strains were highly variable and warrant classification as two distinct virus species. In addition, sequencing of the previously unclassified Mojuí dos Campos (MDCV) and Kaeng Khoi (KKV) viruses showed that both are closely related to NDV. This was unexpected considering that these viruses were isolated in South America and Southeast Asia, respectively, and are mainly associated with bats. Further, our experiments also indicated that BWAV and PGAV, as well as NDV, MDCV and KKV, are able to infect both bat and mosquito cell lines, suggesting that ecological studies focusing on these potential host and vector species are warranted. In the future, the availability of complete genetic information for these viruses, together with an understanding of their genetic relationships, will aid in better defining the distribution and public health impact of these viruses.

Bats as a continuing source of emerging infections in humans

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

Bats: important reservoir hosts of emerging viruses

Bats (order Chiroptera, suborders Megachiroptera ["flying foxes"] and Microchiroptera) are abundant, diverse, and geographically widespread. These mammals provide us with resources, but their importance is minimized and many of their populations and species are at risk, even threatened or endangered. Some of their characteristics (food choices, colonial or solitary nature, population structure, ability to fly, seasonal migration and daily movement patterns, torpor and hibernation, life span, roosting behaviors, ability to echolocate, virus susceptibility) make them exquisitely suitable hosts of viruses and other disease agents. Bats of certain species are well recognized as being capable of transmitting rabies virus, but recent observations of outbreaks and epidemics of newly recognized human and livestock diseases caused by viruses transmitted by various megachiropteran and microchiropteran bats have drawn attention anew to these remarkable mammals. This paper summarizes information regarding chiropteran characteristics and information regarding 66 viruses that have been isolated from bats. From these summaries, it is clear that we do not know enough about bat biology; we are doing too little in terms of bat conservation; and there remain a multitude of questions regarding the role of bats in disease emergence.