Introduction
Bats are an ancient and diverse group of ecologically important mammals, constituting almost a quarter of all mammalian diversity and inhabiting every continent except Antarctica (Arinjay Banerjee et al 2019). They are the second most widespread order of mammals, surpassed only Primates due to the wide distribution of humans.
Taxonomically, bats are grouped in the order Chiroptera with more than 1300 species and as the name suggests, they have morphological and physiological adaptations for powered flight (Ricardo M. 2015). These characteristics and the ecosystem services they provide set them apart from all other mammals. In addition to the important role that bats play in the preservation of ecological balance, they have also been speculated to harbor a wide variety of viruses. The huge diversity of bat species can provide a large breeding ground for viruses. In addition, bats are ancient species and can be traced back to 52.5 million years ago (Hui-Ju Han et.al 2015). The long evolutionary history provides long period for a variety of viruses to co-evolve with bats to make bats their natural reservoirs.
More than 200 viruses have been isolated from or detected in bats. Bats have been considered as natural reservoirs of several highly pathogenic viruses, including Ebola virus, SARS-CoV, MERS-CoV, Nipah virus and Hendra viruses. With human encroachment on natural areas intensifying, particularly in those with high biological richness and bats recognized as important reservoirs of zoonotic viruses (Luis et al 2013). Many of the viruses in bats can cause disease in humans and agriculturally important animal species. These viruses include lyssaviruses, filoviruses, henipaviruses, and coronaviruses.
Coronaviruses
The emergence of a highly pathogenic human coronavirus from China in 2019 named as COVID-19 has sparked more interest in human coronavirus. In 2012 there was similar emergence of virus that was called as Middle East respiratory syndrome coronavirus (MERS-CoV) and before that, in 2003 the known human emergence of the highly fatal human severe acrute respiratory syndrome coronavirus (SARS-CoV) had emerged from China. Even though there has been past outbreaks still there are gaps in understanding the novel coronavirus 2019. Emerging pathogens present a unique challenge to science and medicine because generally little is known about them before they emerge from often-unrecognized zoonotic sources (Christopher M. Coleman 2014)
The coronavirus family is the largest in the order Nidovirales. Coronaviridae consists of two subfamilies, Letovirinae and Ortho-coronavirinae. Within the subfamily Ortho-coronavirinae, there are four genera: alph-acoronavirus, beta-coronavirus, gamma-coronavirus and deltacoronavirus. Alpha-coronaviruses and beta-coronaviruses are found in mammals, whereas gamma-coronaviruses and delta-coronaviruses are primarily found in birds (Woo PC 2010). Currently, there are four coronaviruses that have been recognized to cause the common cold in humans, HCoV-OC43, HCoV-NL63, HCoV-HKU1, and HCoV-229E, and two emerging coronaviruses, SARS-CoV and MERS-CoV, that can cause highly pathogenic respiratory infections.
Many of these coronaviruses appear to have origin in a variety of bat species. With the advent of next generation sequencing technology and increased surveillance of wild animal species, an enormous number of novel coronaviruses have been identified. To date, over 200 novel coronaviruses have been identified in bats and approximately 35% of the bat virome sequenced to date is composed of coronaviruses (Arinjay Banerjee 2019).
References
1. Banerjee A, Kulcsar K, Misra V, Frieman M, Mossman K. Bats and Coronaviruses. Viruses. 2019;11(1):41. Published 2019 Jan 9. doi:10.3390/v11010041
2. Moratelli R, Calisher CH. Bats and zoonotic viruses: can we confidently link bats with emerging deadly viruses?. Mem Inst Oswaldo Cruz. 2015;110(1):1–22. doi:10.1590/0074-02760150048
3. Luis AD, Hayman DT, O’Shea TJ, Cryan PM, Gilbert AT, Pulliam JR, Mills JN, Timonin ME, Willis CK, Cunningham AA, Fooks AR, Rupprecht CE, Wood JL, Webb CT Proc Biol Sci. 2013 Apr 7; 280(1756):20122753.
4. Woo PC, Huang Y, Lau SK, Yuen KY Viruses. 2010 Aug; 2(8):1804-20.
5. Coleman CM, Frieman MB. Coronaviruses: important emerging human pathogens. J Virol. 2014;88(10):5209–5212. doi:10.1128/JVI.03488-13
6. W.C. Clyde, S.N. Koch, P.L. Gunnell, G.F.W.S. BartelsLinking the Wasatchian/Bridgerian boundary to the Cenzoic Global Climate Optimum: new magnetostratiographic and isotopic results from South Pass, Wyoming Paleogeogr. Paleodimatol. Paleoecol., 167 (2001), pp. 175-199
7. G.L. JepsenEarly eocene bat from Wyoming Science, 154 (3754) (1966), pp. 1333-1339
8. Hui-Ju Han, Hong-ling Wen, Chuan-Min Zhou, Fang-Fang Chen, Li-Mei Luo, Jian-wei Liu, Xue-Jie Yu, Bats as reservoirs of severe emerging infectious diseases, Virus Research, Volume 205,2015, Pages 1-6, ISSN 0168-1702
9. DBatVir: the database of bat-associated viruses. Chen L, Liu B, Yang J, Jin Q Database (Oxford). 2014; 2014():bau021.
10. WHO