After Bronx tiger tests positive, zoos, reserves put on high alert
This was in response to the report of a Malayan tiger testing positive for SARS-CoV-2 in New York’s Bronx zoo.
The environment ministry on Monday advised the chief wildlife wardens of all states to take immediate steps to prevent the spread of the coronavirus disease (Covid-19) in national parks and tiger reserves, including restricting the movement of people near national parks and sanctuaries.
This was in response to the report of a Malayan tiger testing positive for SARS-CoV-2 in New York’s Bronx zoo.
Is it far-fetched to imagine that wildlife in national parks or outside could be infected with Covid-19? No. In fact, scientists have flagged that information on potential animal hosts of the virus is crucial to deal with the pandemic. This is because the virus could find new hosts, which can infect other animals or lead to the re-emergence of the disease in humans. This kind of possible cross-species transmission of infection can be dangerous, they said.
A few reports of pet cats and dogs testing positive have surfaced in the past couple of months from Belgium and Hong Kong but a Malayan tiger testing positive (first infection in a wild animal after outbreak) has got many scientists worried about the potential of new animal reservoirs for SARS-CoV-2, the virus that causes Covid-19, outside China.
“Inter species transmission is extremely worrisome, whether it be from pangolins, bats, civets or tigers. Clearly mammals are vulnerable but we don’t know enough at this point. From the science so far, it appears that there are multiple strains evolving and the potential to find new reservoirs exist,” said Krithi Karanth, Chief Conservation Scientist at Centre for Wildlife Studies and Adjunct Associate Professor, Duke University (USA).
“Human activities, specifically consumption of wild meat, wildlife trade, habitat change and fragmentation, are leading to increasing contact between people and wildlife. Multiple zoonotic diseases have emerged, resulting in transmissions between wildlife, domestic animals and people. Covid-19 is perhaps the most destructive example,” she added.
On Monday, the National Tiger Conservation Authority (NTCA) also directed states to observe tigers for symptoms like dry cough or laboured breathing through direct observation and camera trapping, careful handling of post mortem of dead tigers in consultation with state veterinary officials and safeguarding of staff with personal protective equipment (PPE), among others. NTCA has asked states to send samples of suspected cases to laboratories approved by the Indian Council for Agricultural Research.
The Central Zoo Authority of India (CZAI) also issued an advisory to all zoos in India, asking them to remain on high alert and monitor animals for any abnormal behaviour. Samples of any suspect animals, if any, have to be sent to animal health institutes to initiate Covid-19 testing, the advisory added.
“Sometime in the past at an unknown time the SARS-CoV-2 crossed over to humans through an intermediate host. But we haven’t found that host animal. Cross-species transmissions happen all the time. The case of the tiger getting infected in Bronx tells me a few things. First, that there is a lot of infection in New York. Second, we should study if cross-species transmission is happening. Best would be to sequence the virus in the tiger and the humans working close to the tiger and to see the variables. We must also study the tiger very closely to see how long and how much virus it is shedding, and finally investigate if the human got infected by the tiger or vice versa. A body of knowledge on this is very important at this point,” said a senior virologist, who declined to be named because of government advisories on not commenting on Covid-19.
This can be done with more tests in labs and natural conditions, scientists said. “I’m not sure we have enough evidence to say that the Covid-19 virus has several potential animal reservoir hosts based on current spillback (transmission from humans to animals) evidence. We need to do a lot more testing and lab experiments to see if any other species can maintain reservoir host status for this virus. Thus far, all we know is that a few cases of spillback have been observed. What are the consequences of this? Does the animal get sick? Is it able to transmit the virus via the same routes (aerosol or droplets)? These are all questions that need further investigation,” said Abi Tamim Vanak, fellow, Wellcome Trust and senior fellow at Ashoka Trust for Research in Ecology and the Environment.
“We do not know much about the condition of the animals inside the forests, There is a possibility of tigers contracting the infection. So we have asked field staff to observe the animals very carefully and look for signs of Covid-19 while conducting post mortem,” said AK Nayak, member secretary, NTCA.
Several scientific studies in the past have shown how coronaviruses are common among several wild species, including bats, pangolins, racoon dogs, masked palm civet, monkeys and mice. According to United Nations Environment Programme (UNEP), 75% of all emerging infectious diseases in humans are zoonotic and that these zoonotic diseases are closely interlinked with the health of ecosystems.
While scientists have been stressing on the impact of loss of biodiversity, a new study estimated that there has been a 71.5% reduction in large forest patches (> 10,000 km sq) in Central India and the Western Ghats if the existing size of forest patches are compared to a scenario that excludes land taken up by infrastructural projects. The study, by scientists from the Foundation for Ecological Research, Advocacy and Learning (India), Centre for Wildlife Studies (India), University of Goettingen (Germany) and Columbia University (US), was released on Monday.
