A four-year-old Malayan tiger named Nadia, who tested coronavirus disease (Covid-19) positive in New York’s Bronx Zoo on Sunday has raised concerns about the risk of cross-species transmission. But to detect such transmission and the risk of future pandemics, a lot of resources need to be invested in surveillance of animals as well to understand how Covid-19 is impacting them. Uma Ramakrishnan, associate professor, National Centre for Biological Sciences, Bengaluru, and senior fellow, Wellcome Trust, underlined the need to study possible reservoirs of SARS-CoV-2, which causes Covid-19.
Q. Is there a chance that the virus will find a new animal reservoir outside China?
A. It’s possible, but overall, humans are the most numerous species on earth and currently, the virus is infecting them.
Q. How can scientists track animal reservoirs?
A. This is a great question! We could. First, conduct a survey among asymptomatic wildlife/possible reservoirs and look for Covid-19 sequences. We would do this most likely in bats because they carry a high burden of viruses. We could also look for situations where bats are in contact with humans such as the bat harvest we have studied in Nagaland. Second, test animals that show symptoms in zoos or the wild. Regardless, what we will need to do is lots of surveillance! This will require lots of fieldwork and sampling, as well as detailed molecular characterisation and testing, and also genome sequencing to better understand the transmission dynamics (where is spillover happening, from which species to which species). This is an exciting field but poorly represented in India. Almost no such work exists.
Q. What does the tiger testing positive in Bronx Zoo tell us about the susceptibility of wildlife to the virus?
A. Not too much, just that tigers can get infected naturally.
The papers that have been published already told us this, but in that case, the cats were infected on purpose. Here, the tiger contracted it possibly from an asymptomatic carrier. What we do not know is how are tigers affected in general. Is there mortality? And, at what rate?
Q. What does this mean for wildlife?
A. In zoos, contact between humans and captive animals is high. Is this the case at all in the wild? It might be that the chances of transmission are much lower for wild animals (while could be a chain: humans to macaques to tigers, for example), and does this happen? These are all questions that would need to be addressed from both a basic and applied perspective.
