Pangolins are not likely the direct source of the novel coronavirus pandemic infecting humans around the planet, according to a new genetic analysis conducted in three sick pangolins.
Previous studies showed that SARS-CoV-2, the novel coronavirus responsible for Covid-19 respiratory disease, originated from bats but jumped to humans through an intermediary host. Some scientists suggest that pangolins, the most illegally trafficked mammals in the world, may have played a key role in the pandemic, arguing that SARS-CoV-2 likely jumped from bats to humans through a middle-carrier. The armored animals are hunted largely for their scales, which are believed to by traditional medicine practitioners to hold a number of health benefits, putting them into close contact with humans. In the last 45 years, the number of pangolins killed has increased by 150 percent, contributing to a total trade ban.
Illegally trafficked pangolins, also known as scaly anteaters, were found to carry closely related coronaviruses of the pandemic strain, however, the animal’s unique genetic makeup may protect them from the intense immune responses seen in humans infected with the coronavirus.
Coronaviruses are known to infect animals but it is rare that they evolve and jump to humans. In April, six new strains were detected in bats – none of which are known to pose a risk to humans. Identifying and targeting these coronaviruses for future research serve as an important opportunity in preventing a future outbreak from “spillover events” like those seen in 2003 with Severe Acute Respiratory Syndrome (SARS), the 2015 Middle East Respiratory Syndrome (MERS) outbreak, and the current SARS-CoV-2 pandemic.
Researchers at the Guangdong Institute of Applied Biological Resources examined whether pangolins could have served as that intermediate host by assembling the whole genome of a coronavirus that has been identified in three sick Malayan pangolins from two groups, which were likely to be smuggled for black market trade. The results indicate that the pangolin coronavirus is genetically similar to SARS-CoV-2 as well as a group of bat coronaviruses, but not likely its precursor.
“The molecular and phylogenetic analyses showed that this pangolin virus (pangolin-CoV-2020) is genetically related to the SARS-CoV-2, as well as a group of bat coronaviruses, but do not support the SARS-CoV-2 emerged directly from pangolin-CoV-2020,” write the authors in PLOS Pathogens.
Pangolins are natural hosts of coronaviruses but is not likely that the scaled animals served as an intermediary host for the novel coronavirus, jumping from bats to humans. However, it is possible that other coronaviruses could be circulating in pangolins, such as betacoronaviruses that have an “unknown potential to infect humans.”
The exact source of SARS-CoV-2 is still unknown and the researchers argue that in order to combat the potential for spillovers in the future, global surveillance of coronaviruses in pangolins is needed as well as a revised relationship between humans and the wild world.
“Large surveillance of coronaviruses in pangolins could improve our understanding of the spectrum of coronaviruses in pangolins,” note the researchers. “In addition to [the] conservation of wildlife, minimizing the exposures of humans to wildlife will be important to reduce the spillover risks of coronaviruses from wild animals to humans.”