Cross-species transmission unlikely from coronavirus infected Asiatic lions
doi:10.1038/nindia.2021.66 Published online 6 May 2021
Scientists have ruled out cross-species transmission of SARS-CoV-2 to other animals after eight Asiatic lions at a zoo in Hyderabad tested positive for the coronavirus – and have since been treated.
The scientists at Hyderabad-based Centre for Cellular and Molecular Biology (CCMB) sequenced the virus genome from the animal samples. CCMB director Rakesh Mishra told Nature India that the chance of cross-transmission of the SARS-CoV-2 virus from one animal species to another is "very, very low". Some of the infected lions showed mild symptoms and most were asymptomatic.
In late April 2021, the zoo authorities collected nose, throat and respiratory tract samples from the animals under anaesthesia when they showed signs of respiratory distress associated with COVID-19. Since this is not an ideal way to collect samples, CCMB is now devising a new method to test faecal samples from infected animals and standardising a testing procedure to monitor animal infections.
"Jumping species does not happen commonly — it is a rare event,” says virologist Gagandeep Kang, a professor at the Christian Medical College in Vellore. Viruses tend to be host-restricted and need a specific protein to act as a receptor. "But there are other accessory factors responsible for attachment and invasion by the virus," she says.
Lions are “incidental hosts” for the coronavirus and infection in the big cats is unlikely to be fatal, says N V K Ashraf, Senior Director and Chief Veterinarian at the Wildlife Trust of India. Incidental transmissions mostly occur in captive situations, where the animals have regular contact with infected humans, he says. The possibility of infection in the wild are remote.
This is unlike the case of canine distemper that killed many Asiatic lions in 2018, Ashraf says. In September 2018, an infection caused by the canine distemper virus (CDV), normally found in dogs, emerged in Asiatic lions in India. The National Institute of Virology in Pune detected the virus in samples from 68 lions and 6 leopards. CDV has been reported in lions, tigers, red pandas, and leopards from zoos and forests in India1 with free- ranging dog populations often posing a threat of CDV transmission to wildlife.
“There are feline-specific coronaviruses in nature, which can mutate to cause feline infectious peritonitis (FIP),” says Ashraf.
Eric Leroy, a specialist in zoonotic viruses at the Institute for Research for Development (IRD) in France says animal to animal transmission of COVID-19 has not been reported till now. "Therefore, the likelihood of SARS-CoV-2 transmission from Asian tigers to lions or to other kinds of animals is probably weak.” In April 2020, Leroy and colleagues studied the risk of transmission of SARS-CoV-2 in domestic pets and wild animals2 to find that infections manifest as asymptomatic or mild disease in in dogs and cats.
The first COVID-19 case in a companion animal was reported in a Pomeranian dog from Hong Kong in February 2020, and later from a pet cat in March 2020 in China3. In both cases, their owners were infected with the virus previously, and the genetic sequence of the SARS-CoV-2 from the owner and the pets was similar. Other cases of pet animal infections were also reported from Belgium, France, Germany, Russia and the United States, and tigers, lions, and minks in Denmark, Netherlands, USA, and Spain4.
The U.S. Center for Disease Control (CDC) advises people with suspected or confirmed COVID-19 to avoid contact with animals, including pets, livestock, and wildlife.
1. Mourya, D. V. et al. Canine Distemper Virus in Asiatic Lions of Gujarat State, India. Emerg Infect Dis. 25, 2128–2130 (2019) doi: 10.3201/eid2511.190120
2. Leroy, E. M. et al. The risk of SARS-CoV-2 transmission to pets and other wild and domestic animals strongly mandates a one-health strategy to control the COVID-19 pandemic. One Health. 10, 100133 (2020) doi: 10.1016/j.onehlt.2020.100133
3. Kiros, M. et al. COVID-19 pandemic: current knowledge about the role of pets and other animals in disease transmission. Virol. J. 17, 143 (2020) doi: 10.1186/s12985-020-01416-9
4. Mahdy, M. A. A. et al. An Overview of SARS-CoV-2 and Animal Infection. Front. Vet. Sci., 11 (2020) doi: 10.3389/fvets.2020.596391