Twin Mammals and COVID-19: Life and Science of the Suspects

The world is puzzling over the origin of the current outbreak of the coronavirus disease (COVID-19) that is caused by a novel coronavirus-2019 (2019-nCoV). As of 25 th March 2020, the World Health Organization has reported 4,14,179 confirmed cases and 18,440 confirmed deaths in total due to COVID-19. To this end, two unique mammals namely bats and pangolins are being investigated for their potential link to COVID-19. However, the evidence so far gathered in this context is far from clear. This paper aimed to: (i) enlighten the major aspects of life of bats and pangolins; (ii) briefly discusses their potential link to COVID-19; and also (iii) to highlight the way forward. The outcomes may contribute to future research on the subject.


Introduction
In humans, several respiratory infections ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) are known to be due a large family of viruses called as coronaviruses. On 31 st December 2019, the World Health Organization (WHO) was informed of a cluster of cases of pneumonia of unknown cause detected in Wuhan City, Hubei Province of China. Later, the WHO named an infectious disease as the coronavirus disease  and confirmed as to worldwide pandemic outbreak caused by a newly discovered coronavirus the novel coronavirus (2019-nCoV). The world is puzzling over the origin of COVID-19. In fact, COVID-19 is one of the infectious diseases (zoonotic diseases or zoonoses) that are transmitted between species from animals to humans (or from humans to animals). As of 25 th March 2020, the World Health Organization has reported 41,4,179 confirmed cases, 18,440 confirmed deaths in total due to COVID-19 (WHO 2020 a ) ( Table 1). The WHO has declared the COVID-19 outbreak a global health emergency. Notably, two unique mammals namely bats and pangolins are being investigated for their potential link to  However, the evidence so far gathered in this context is far from clear. Given above, in this paper, the major aspects of life of bats and pangolins are enlightened; recent reports on the potential link of bats and pangolins to COVID-19 are briefly discussed; and also the way forward is highlighted.

Bats
Bat is an exceptional creature and remarkable flying social mammal, and belongs to order Chiroptera and family Microchiroptera. Bats are divided into two main types: megabats (sub-order: Megachiroptera) and microbats (sub-order: Microchiroptera). Megabats include flying foxes and Old-World fruit bats, roost in trees, are the largest type of bats, have great eyesight and most eat fruit or nectar.
On the other, microbats are smaller in size; most live in the Western Hemisphere and most eat insects (insectivorous) using their echolocation ability. Bats exhibit a great variation in body size, weight, lifespan and food habit.
There occurs a relationship between the body size and the lifespan of mammals, where, the larger mammals are assumed to live longer lives. Against this relationship, the lifespan of bats may range between 10 -25 years, and can live over 30 years in the wild (Wund and Myers 2005). Additionally, hibernating bats have a tendency to live longer than non-hibernating ones; and the females live longer than males depending on their species. Bats are omnivores and most bats eat insects, but many feed on leaves, pollen, nectar, petals, bracts, fruits (such as avocados, mangoes, bananas and wild dates) or seeds.

Pangolins
The solitary, primarily nocturnal and scaly anteaters, pangolins are mammals and belong to the order Pholidota and family Manidae.

Potential link of bats and pangolins to COVID-19
The novel coronavirus ( To varying extents, both pangolins and bats are eaten in China and other parts of world. As mentioned also above that pangolins are highly sought-after in China for their meat and their scales; the latter are used in traditional medicine. Bats are also traditionally eaten in Indonesia by the Minahasan people from North Sulawesi as whole bats including the head and wings in the form of a curry-like dish called Paniki (Reuters News, https://www.reuters.com/article/us-chinahealth-indonesia-bats/bat-meat-still-popular-in-parts-of-indonesia-despitecoronavirus-fears-idUSKBN20511R).
In the present context, series of studies have been done in order to reveal the connection of bats with the mentioned COVID-19. However, the transmission routine of COVID-19-causing 2019-nCoV virus among hosts is yet to reveal (Zhou et al. 2020). Mystery deepens also over animal source of coronavirus, where both the mammals, namely ant-eating pangolins and mostly-insect eating bats are considered as prime suspects Zhou et al. 2020).
Notably, both pangolins and bats are unique in the sense that the former is the only known mammal with large, protective keratin scales covering their skin. On the other, bats are remarkable flying social mammals with true wings and flight.