A wild Indian Leopard has been found to be infected with SARS-CoV-2, the virus that causes COVID-19. It’s unclear how the free-ranging big cat caught the infection, but the researcher’s preliminary study suggests it was “possibly” the result of a spillover from humans.
The researchers' findings, which are yet to be peer-reviewed, were recently published on the pre-print server bioRxiv.
The carcass of the young male leopard cub was discovered in October 2021 near a farm in rural Uttar Pradesh, located approximately 160 kilometers (99 miles) from the Indian capital New Delhi. Researchers from the Indian Veterinary Research Institute carried out a necropsy of the animal wearing full PPE and found the leopard died of numerous injuries to its head and neck, likely caused by another animal.
The unusual discovery of SARS-CoV-2 came from a nasal swab of the animal. The team sequenced the sample and detected the presence of the Delta variant of SARs-CoV-2. Brain, spleen, lymph node, and lungs specimens were found positive for the virus strengthening the view that this wasn’t simply a case of cross-contamination. The researchers explain that the “high resemblance of spike protein sequences with that of human Delta variant suggests possible spillover infection and no major genetic changes in the spike protein upon species cross over.”
The Delta variant of the virus was first identified in India towards the end of 2020, sparking a catastrophic second wave in the following months. However, when this dead leopard was discovered in October 2021, cases in India had started to ease and COVID-19 was not especially prolific in the local rural area.
This raises the question of how the young cub became infected. It's known that other species of leopard and big cat can be infected with the virus as veterinarians have detected cases in zoos. The novel coronavirus has been documented in cats, dogs, tigers, mink, and a bunch of other species too, but this is the first instance of a wild big cat infected with the virus. However, leopards are marginally less shy with humans compared to other wild cats and interactions with people are becoming increasingly common, primarily because ever-expanding agricultural growth is encroaching on their natural habitat.
Wild animals infected with SARS-CoV-2 raise another problem. Recent research has indicated that the virus could be prolific among wild White-tailed deer in some parts of the US. While this is purely speculative for now, a SARS-CoV-2 infection of a wild animal host could potentially result in that animal population becoming a reservoir that drives the emergence of new variants with risk of spillback to humans.
The risk of one leopard in rural India is extremely low, but researchers believe their work affirms this concern and the need to stay wary.
“Detection of SARS-CoV-2 in free-ranging leopard when incidences of human COVID19 have dropped to significantly lower level underlines the necessity to intensify the screening and check for development of carrier status in wild felids,” the paper concludes.