Emerging and reemerging of zoonotic pathogens has posed an intense challenge to human even in the modern world. Even with the rapid advancement in technology and healthcare settings, we have never been closer to the victory in fighting against these infectious diseases. The emerging of highly pathogenic diseases in the past few decades, including AIDS, Ebola fever, avian influenza, neurological and respiratory diseases caused by Hendra and Nipah viruses, and SARS etc., caused enormous losses in economy and human lives. These zoonotic events have also demonstrated the vulnerability of the health of human and domestic animals.
The expanding human population has shaped the emergence of infectious diseases in human or poultry by sustaining disease transmission with extremely high population density that did not exist anywhere in the world before (6, 28). Previous analysis has also shown that more than 70% of emerging or reemerging pathogens are known to be zoonotic (29), and many of these emerging infections are associated with wildlife (4). These observations suggested that human encroachment on wildlife habitats has caused the exposure of previously unknown pathogens in wild animals and resulted in increased transmissions between human, domestic animals and wildlife. The continuous expanding of animal farm industry together with the frequent travelling of human and livestock across different continents have also favored the transmission of these novel pathogens in immunological naïve human and animal populations worldwide. Researchers have also found that a significant portion of these newly emerged or reemerged pathogens are RNA viruses (29). An explanation for this is that RNA viruses might have much higher nucleotide mutation rates than those pathogens that have a DNA genome, thereby allowing the RNA viruses to better adapt to a new host (7).
Many emerging pathogens of human, domestic animals are assumed to be maintained in wildlife. However, many of these reservoirs for emerging viruses have never been identified. These perhaps reflect our poor understandings of animal pathogens circulating in the wildlife. Among different wild animals, bats might be one of the relatively well-studied wild animal populations in terms of zoonotic disease concerns. So far, over 60 viruses, including members from families of Rhabdoviridae, Orthomyxoviridae, Paramyxoviridae, Coronaviridae, Togaviridae, Flaviviridae, Bunyaviridae, Reoviridae, Arenaviridae, Herpesviridae and Picornaviridae, have been isolated or detected from different bat species (1, 20). Of these identified bat viruses, some are found to be the causative agents of disease in human (e.g. Ebola virus, Menangle virus, Rabies virus, Hendra virus and Nipah virus). It should be noted that bats represent the second largest order of mammals after rodents. The species richness of bats may harbor a great variety of viruses, thereby increasing the chances of generating viruses which can cross the species barrier. In addition, with its unique ability to fly and other special features (e.g. migration in some bat species), bats might have important roles for transmitting zoonotic pathogens to other animals and human. Here, we share our recent experiences on the discoveries of bat coronaviruses and astroviruses as examples to highlight this possibility.
Novel Coronaviruses and Astroviruses in Bats
- Received Date: 20 January 2009
- Accepted Date: 10 February 2009
Abstract: Zoonotic transmissions of emerging pathogens from wildlife to human have shaped the history of mankind. These events have also highlighted our poor understanding of microorganisms circulated in wild animals. Coronaviruses and astroviruses, which can be found from a wide range of mammals, were recently detected in bats. Strikingly, these bat viruses are genetically highly diverse and these interesting findings might help to better understand the evolution and ecology of these viruses. The discoveries of these novel bats viruses not only suggested that bats are important hosts for these virus families, but also reiterated the role of bats as a reservoir of viruses that might pose a zoonotic threat to human health.