Retroviruses of Bats: a Threat Waiting in the Wings? (original) (raw)

Bats: carriers of zoonotic viral and emerging infectious diseases

Journal of Experimental Biology and Agricultural Sciences, 2016

Bats are reported as reservoir host for several viruses, which cause significant illness in human and animals. Some of the bat transmitted zoonotic viral diseases such as Ebola, Hendra, Nipah and rabies may cause severe human casualties. They also harbor several other viruses such as MERS and SARS corona viruses, which may cause disease in human through direct spillover to human or through an intermediate host or vectors. Being reservoir hosts bats do not get affected by these viruses. This probably may happen due to the specificity of bat immune system, which reacts differently with viral pathogens in comparison to their other mammalian counterparts. Although bats are important reservoir hosts for several zoonotic viruses, very little information is available regarding host/virus relationships as only few experimental studies have been done on bat colonies, lack of expertise for study of bat immunology and antiviral responses and difficulty in conducting field work. However, with t...

Bats and zoonotic viruses: can we confidently link bats with emerging deadly viruses?

An increasingly asked question is ‘can we confidently link bats with emerging viruses?’. No, or not yet, is the qualified answer based on the evidence available. Although more than 200 viruses – some of them deadly zoonotic viruses – have been isolated from or otherwise detected in bats, the supposed connections between bats, bat viruses and human diseases have been raised more on speculation than on evidence supporting their direct or indirect roles in the epidemiology of diseases (except for rabies). However, we are convinced that the evidence points in that direction and that at some point it will be proved that bats are competent hosts for at least a few zoonotic viruses. In this review, we cover aspects of bat biology, ecology and evolution that might be relevant in medical investigations and we provide a historical synthesis of some disease outbreaks causally linked to bats. We provide evolutionary-based hypotheses to tentatively explain the viral transmission route through mammalian intermediate hosts and to explain the geographic concentration of most outbreaks, but both are no more than speculations that still require formal assessment.

Bats and viruses: a death-defying friendship

VirusDisease, 2021

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. Keywords Bat Á Emerging viruses Á Nipah virus Á Rabies virus Á Sosuga virus Á Menangle virus Á Tioman virus Á Ebola virus Á Hanta virus Á Corona viruses

Infectious KoRV-related retroviruses circulating in Australian bats

Proceedings of the National Academy of Sciences

Bats are reservoirs of emerging viruses that are highly pathogenic to other mammals, including humans. Despite the diversity and abundance of bat viruses, to date they have not been shown to harbor exogenous retroviruses. Here we report the discovery and characterization of a group of koala retrovirus-related (KoRV-related) gammaretroviruses in Australian and Asian bats. These include the Hervey pteropid gammaretrovirus (HPG), identified in the scat of the Australian black flying fox (Pteropus alecto), which is the first reproduction-competent retrovirus found in bats. HPG is a close relative of KoRV and the gibbon ape leukemia virus (GALV), with virion morphology and Mn2+-dependent virion-associated reverse transcriptase activity typical of a gammaretrovirus. In vitro, HPG is capable of infecting bat and human cells, but not mouse cells, and displays a similar pattern of cell tropism as KoRV-A and GALV. Population studies reveal the presence of HPG and KoRV-related sequences in sev...

Bats host the most virulent—but not the most dangerous—zoonotic viruses

Identifying virus characteristics associated with the largest public health impacts on human populations is critical to informing zoonotic risk assessments and surveillance strategies. Efforts to assess “zoonotic risk” often use trait-based analyses to identify which viral and reservoir host groups are most likely to source zoonoses but have not fully addressed how and why the impacts of zoonotic viruses vary in terms of disease severity (‘virulence’), capacity to spread within human populations (‘transmissibility’), or total human mortality (‘death burden’). We analyzed trends in human case fatality rates, transmission capacities, and total death burdens across a comprehensive dataset of mammalian and avian zoonotic viruses. Bats harbor the most virulent zoonotic viruses even when compared to birds, which alongside bats, have been hypothesized to be “special” zoonotic reservoirs due to molecular adaptations that support the physiology of flight. Reservoir host groups more closely r...