The possible role of bats in COVID-19

FOR MOST of the public, the term ‘coronavirus’ wasn’t well known until a few months ago, when a mysterious ailment started to spread through China and then to the rest of the world.

Coronaviruses belong to a group of RNA viruses that cause a variety of diseases in humans and other animals. The word ‘corona’ means crown in Spanish. Coronaviruses, so named because of their appearance, are covered with crown-like spikes.

SAR-CoV-2 is a single-stranded RNA virus. It is contagious in humans and is the cause of the ongoing pandemic of Coronavirus Disease 2019 (COVID-19) that has been designated a Public Health Emergency of International Concern by the World Health Organization. COVID-19 is the infectious disease caused by the most recently discovered coronavirus. This new virus and disease were unknown before the outbreak began in Wuhan, China, in December 2019.

In humans, several coronaviruses are known to cause respiratory infections ranging from the common cold to more severe diseases, such as the Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS). Both MERS and SARS are zoonotic viruses, meaning they are transmitted from animals to humans. SAR-CoV-2 has close genetic similarity to bat coronaviruses and, therefore, likely originated from bats.

EFFICIENT CARRIERS

It is known that bats are reservoirs for several different deadly viruses, including Ebola, Rabies, SARS and MERS, with the latter two coronaviruses being similar to the one that is now causing a global pandemic. It is theorised that bats, as the only flying mammals, have evolved to become efficient carriers of coronaviruses. The act of flying elevates the bat’s metabolism and body temperature boosting a bat’s immune system and making it more tolerant of viruses. Scientists have found some promising leads in the animal’s genetic make-up to back up this hypothesis.

Often an intermediate host is involved in the viral transmission. An intermediate host or vector transfers the parasite from the original host to the final host species. In the case of SARS in 2003, it was the civet cat. In the case of the virus causing MERS later in the 2000s, the intermediate hosts were camels. In the case of COVID-19, it is possible that the Chinese Horseshoe Bat, a common bat species in China, was the original host and the pangolin – a scaled anteater often sold as meat in Chinese markets even though it is banned – could be the intermediate host.

It is too early to say conclusively that COVID-19 originated in bats and whether an intermediary played a role as more research is needed. However, scientists warn that deforestation and urbanisation, especially in densely populated areas, are putting humans into closer contact with bats and other animals, which more easily allows the spillover of viruses.

Bats play important roles in many environments with some plants, including bananas, mangoes, avocadoes, figs, guavas and cashews, depending partly or wholly on bats to pollinate their flowers or spread their seeds. Other bats (insectivores) also help control pests by eating insects.

Bats, pangolins and other wildlife should not be persecuted as the cause of COVID-19 pandemic; rather, humans should limit their contact with wild animals and desist from hunting and trading in wildlife. There are over 1,200 bat species worldwide and Jamaica has 21 species of bats, five of which are found nowhere else on earth.

Contributed by Elizabeth Morrison, zoologist, and Dionne Newell, entomology, senior research officer, Natural History Museum of Jamaica, Institute of Jamaica.